Smart Pioneers

The making of a Classic Portland Snowstorm.

Just a short post about the weather because its the middle of winter and we just experienced a classic Portland winter situation. It wasn’t major or destructive but it was a classic set up that a gardener should be aware of in the future because it has happened innumerable times in the past and it will happen in the future. I’ll try to explain it in a way that is easy to understand and show some of the things to look for and how a classic Portland snow/ice storm sets up.

The Jet Stream and damn cold

We had a remarkably active jet stream throughout the month of December. It landed us with a record amount of rain for the month and aside from sodden hillsides and swollen rivers it pretty much soaked our gardens. For several weeks warm, then progressively colder storms streamed in, soaked us and then repeated. So it was not a surprise at all when the jet stream not only backed off it split. VERY El Nino. In fact, research shows that the strongest El Ninos produce some pretty prodigious rains for the PNW before turning the Jet Stream to the south. In the last week of December what is known as a REX block stopped storms from impinging on our region. High pressure- thats air that is sinking and drying- in a clockwise motion stopped the storms and with a slight northeast bent it ushered in very cold, (not quite arctic) dry air east of the Cascades. The jet stream dropped to our south into Northern California.

ICE STORMWintery Scene



A Bora Wind

Cold high pressure enveloped the Columbia Basin where dense dry and almost arctic air collected. The Columbia River Gorge is a sea level path through the mountains. As low pressure centers rode the jet stream into N. California it set up a dynamic sucking the cold dry air through the Gorge. So- there was low pressure to the south west and high pressure to the north east. The perfect set up for an easterly flow. Air flows from high to low pressure and in this configuration its sent blasting through the gorge.  A Bora wind. This steep pressure gradient was responsible for the wind that lashed Portland for several days at the end of December and beginning of the New Year. A pressure gradient can be likened to a ball rolling down a slope. The steeper the slope (closer the bars of pressure are aligned ) the faster the ball rolls and the steeper the gradient the faster the air goes. Confined to the slim width of the Gorge and you have yourself some wind. On top of this the Columbia Basin and eastern Oregon, the source of our cold air was refrigerating in a large and expansive low elevation snow pack. Cold. As you were aware  that frigid air moved into the Portland area and down the Valley. It even blasted out of the east facing canyons at the beach.

Dewpoint, down, down, down

Two things to watch when an east wind (Bora) wind sets up are the temperatures at the source of the wind and then the dew point. Cold air is dry air- the colder it is the less moisture air can hold. (The molecules are closer together). Without going into graphic detail, lets just say that you should be aware of the dew point in Troutdale because they are at the front doorway of cold dry conditions. I watched the dew point dip day after day through the twenties and down into the teens. Tell tale signs of not only the measure of the atmosphere but the depth of cold air at the surface. Typically several days into an east wind event the temperatures at Troutdale will not plunge- but the mixing of the air will keep the temperature up. The dew point however, is where to look, it edges steadily lower. The other important clue is the temperatures east of the Cascades. If it is in the teens or single digits in Pendleton and the teens or colder in The Dalles- thats where our air originates and pressure gradients are shipping it to us directly. Those conditions were present.

A (weak) moisture source

What happened on January 2nd was  a classic set up for snow and then freezing rain in Western Oregon. The cold, dry air that had been flooding the western part of the state became entrenched at the surface. Remember, cold air is dense and it follows the contours of the ground- it sticks close to the surface it fills up the valleys and canyons. Slowly, the rex block high pressure that had capped our atmosphere gave way to lower pressure edging north from California. Moisture rode northward and over topped the cold air. I should say that if a storm is strong and comes barreling in it will scour out the cold air at the surface and there is a faster transition. This time, the weakness of the system moving north left the air in place and after days of easterly flow cold air was deep. The first precipitation to fall into that air mass began as snow and ended in freezing rain. The large difference between the air temperature and the dew point (humidity) shows the large depth of cold air. And hence we got about 1.5″ to 2.5″ of fluffy snow in the morning of the 3rd. More was to come.


Grevillea australis all iced up.

A Silver Thaw

This is a term I learned as a child and its fallen out of modern favor instead replaced by more scientific lingo. Yes, we are all becoming junior meteorologists, but from the past I bring up ‘Silver Thaw’ because it was well known to our predecessors and it is so aptly descriptive. Freezing rain occurs when the layer of cold air over us is eroded and over topped by warmer air and moisture. Precipitation begins as snow, falls into warm air and melts and then if the layer of cold air at the surface is deep it refreezes. Technically, this is sleet – its the ice balls that bounce and pelt you. As the warm air becomes deeper (eroding the cold surface air) rain does not refreeze, instead it remains liquid but becomes super cooled and it will freeze on contact with every surface- the temperature is below freezing but rain is falling. Glazing, is the term but I prefer ‘Silver Thaw’- harkening back to true Oregonian roots. Typically, in this set up the East Wind continues to pour cold air into the western valleys and is met by more moisture over riding from the west and south. We were lucky this time that the storm was not particularly wet. Hence, we had only about .25″ of ice and we escaped real tree damage and a prolonged bout. Warm air then wins out- the perfectly applicable term ‘Silver Thaw’. The Pioneers knew what they were talking about.

That may be it for winter

I probably don’t need to point out that the window for truly arctic air to come into our gardens is waning quickly. Typically the final gasp of that kind of air dies around Valentines Day. It can get cold after that and certainly freeze but true arctic air is extremely rare and as far as I am concerned that is spring. So long term forecasts are not showing any real set up for arctic air. We could be out of the woods. I’ll continue to watch it closely and chime in if I see anything that looks dangerous. Until then, we are probably looking at the second zone 9 winter in a row. YAY.


Smart Pioneers

A sample of winning plants that I wouldn’t be without.

I thought I would do a different blog this time. Instead of talking about the weather I decided to share some of the plants that I couldn’t be without. I’m exposed to thousands of plants because of my profession. Greg would agree that we are are total plant whores. I love, love, love finding a new plant and testing it out in my garden. In fact my garden isn’t the most aesthetically consistent. I try new plants all the time. What this entails is plunking the plant straight into my un-ammended soil and getting it established. I figure that most people don’t have the time or resources or continuity to make the soil perfect for individual plants. In my garden its sink or swim. Here are some plants that I think are perfectly adapted to our climate. Plants that I wouldn’t be without.


Agave bracteosa (Zn7a) and Yucca linearifolia (Zn7a)

Agave bracteosa & Yucca linearifolia (Zn7a 0ºF)

Two plants that I find completely indispensable in my garden are these two easy to grow Mexicans. Agave bracteosa is perhaps one of the easiest Agaves to grow in Portland. Sometimes called the Octopus Agave I love its easy ways, and non-lethal leaves. This dear plant thrives in very well drained soil and forms a substantial plant quickly. Mine are located in the partial shade of a ‘Summer Chocolate’ Albizia. I love that it suckers freely and I can detach and move them all around my garden. On a scale of 1-10 I give this remarkably adaptable large succulent a 10.    Just north of the Agave in this picture is another nearly flawless plant. Its the ultimately symmetrical, always erupting stunning Yucca linearifolia. Its a new comer from Mexico as well but it LOVES the gravely well drained soil of my parking strip. I have three in a group and they have been spotless through five winters as well as precipitous lows. Its a perfect plant. I love to stare directly into the rosette, its symmetry is dizzying and always makes me smile, smile, smile. This Yucca has become very rare on the market and all I can advise is buy it immediately if you see it offered. Immediately.

Jasminum officinale ‘Affine’ (Zn7a)

Jasminum offiinale ‘Affine’ (Zn7a 0ºF)

On a totally different note I thought I’d share my favorite vine. Sure, it doesn’t have 6″ wide flowers and smother itself in color but what it does offer I love. Jasminum officinale ‘Affine’ earns top marks in my garden for several reasons. First, its totally adapted to our climate, cold hardy, drought tolerant, and remarkably vigorous. This regal vine, also known as Poet’s Jasmine takes up vertical real estate but its well worth it. Heavily in all of June and then sporadically through summer it delights with clusters of 1″ wide crystal white flowers with the worlds most exquisite perfume. June wouldn’t be June without the wafting perfume of this elegant, romantic vine. In fall the pinnate leaves turn to tones of apricot and fawn before dropping. To 15’+ it deserves a place on every large pergola in western Oregon. New growth on this vigorous cultivar is a stunning deep burgundy. Light summer water and nearly any soil. Full sun to quite a bit of shade.

Fatsia japonica ‘Variegata’ Zn7a

Fatsia japonica ‘Variegata’ (Zn7a 0ºF)

A good friend of mine and the owner of a large nursery in California once told me that “foliage is king”. I have to whole heartedly agree. Fatsia is a wonderful plant to grow in our climate. Its bold and undemanding and suffers the rigors of dry shade with nearly bionic aplomb. My favorite is plain old ‘Variegata’. Its huge evergreen leaves are irreverently edged in white. Perhaps its most remarkable trick is to have huge candelabras of variegated, pure white orbicular flowers in autumn. To 6′ tall and half again as wide. We will have an enormous amount of this exact cultivar for sale in the spring. Deer shun it even as it imparts the toughest display of tropical foliage. Easy and hardy.


Digitalis x ‘Honey Trumpet’ (Zn5b)

Digitalis x ‘Honey Trumpet’ (Zn5b -15ºF)

This is pretty self indulgent but I have to plug this remarkable hybrid Digitalis that emerged at our nursery. The product of a tetraploid yellow foxglove and a semi-shrubby species what you get is a sterile but blooming machine. Tubular amber imbued trumpets line tall spikes from May to October. Cut back the spent scapes on this long lived perennial and more will arise. It thrives in full sun and  many types of  soil. Its Iberian heritage means that it thrives despite our dust dry summers. To 28″ tall and producing multiple scapes. Perfect in a perennial border or adaptable to xeric realms. Regular water in full sun sends this foxglove soaring


Arctostaphylos x ‘White Lanterns’ (Zn7a)

Arctostaphylos x ‘White Lanterns’ (Zn7a 0ºF)

Manzanita. Everyone in our region should have at least one. They are the ultimate shrubs of the west. And WOW what they offer is a four season display of bark, foliage, and flowers. I’ve grown a shitload of Arctostaphylos and I can tell you that some are great garden plants but many species are determined to be feral. This smaller growing shrub is a perfect plant as far as I am concerned. Small, dapper leaves- held perpendicular to the sun to avoid moisture loss- are a fine textured bonanza. To just 3′ x 3′ it finds a home in the smallest gardens. And holy smokes it offers smooth cinnamon bark with age and a reliable display of  profuse white flowers in late winter. As with all in this wild genus it thrives on utter neglect. ‘White Lanterns’ has been a stellar performer at the OSU North Willamette Experimental Station. And I completely agree. Its a fantastic, adaptable, disease free, cold hardy cultivar.

Callistemon viridiflorus (Zn7b)

Callistemon viridiflorus (Zn7b 5ºF)

This groovy bottlebrush should be everywhere. Diamond shaped forest green leaves line the corky white stems. In May-July it erupts in delicious chartreuse brushes. This 7’x 5′ evergreen shrub loves full sun in our climate. Its a boon for pollinators as well as hummingbirds. A native of Tasmania it actually needs cold for a good flower set- and our region is ideal. In its native haunts it dutifully follows cold air drainages in canyons to achieve its perfect adaptation. We have been experimenting with this species and have selected three distinct varietals. ‘Shamrock’ is  a tidy compact but decidedly upright cultivar. ‘Xera Compact’ is exactly that but with an unmatched profusion of bloom. ‘Xera Hedgehog’ is but 2′ x 2′ with a copious display of chartreuse brushes. It could find a perfect home in the sun drenched tough life of parking lot islands. Light summer water.

Osmanthus x fortunei ‘San Jose’ (Zn7b)

Osmanthus x fortunei ‘San Jose’ (Zn7b 5ºF)

I have a thing for fragrance in my garden and when you pair that with a handsome glossy evergreen shrub…woo, I’m there. This hybrid Tea Olive is just the ticket. In time it achieves tree like status but I prefer it as a large shrub with leaves from the ground to the top. In Oct/Nov. it produces small parchment colored flowers with the penetrating perfume of apricot and freesia. Mine is 25′ from my back porch but when the weak but warm autumn sun blazes it sends the perfume on a roaming path to my house. Easily grown in almost any soil, once up and going it is completely tolerant of our summer drought. Whatever you do, don’t forget autumn where some of the most sophisticated plants shine.

Grevillea  miqueliana (Zn7b)

Grevillea miqueliana (Zn7b 5ºF)

This Australian shrub was a pure experiment and its turned into a winner. Round Leaf Grevillea is the not so original common name of this large shrub which is less than common. Undulating round suede textured leaves are dapper year round. This large, dense evergreen shrub is fantastic in bloom from January to July. Pendant sunset colored flowers decorate the tips and delight gardeners as well as hummingbirds. Best with exceptional drainage such as a slope, but one of the most tolerant of clay soils. Grevilleas can be a challenge to grow  but with careful siting and deliberate neglect they are more than rewarding. Last winter we experienced a small freezing rain event. My Grevilleas were in full bloom. Peering out the window I watched as a hummer perched on a stem waiting patiently for the ice encased nectar rich flowers to thaw. A natural bird feeder and an elegant shrub.

Remember every season

We are so gifted in this climate to be able to grow a nearly endless palette of plants. I love testing new plants and I’ve come to respect these as reliable and dynamic additions to the garden. Gardens are not static, we begin them and then follow where they go. This group of plants I encourage you to try, include, enjoy in your own space. I’ll continue to try new and old plants to discern their adaptability. Trial and error is the essence of growing plants. All of these plants we grow at Xera. Have a good early October, one of the nicest times of the year in PDX.



A sample of winning plants that I wouldn’t be without.

Summer 2016 and the blob redux

I can say that I’ve observed the summer weather in Western Oregon for more than 40 years- yes i was a geek that far back- and you if you guess my age based on that you will be pleasantly surprised that it all began in elementary school. I grew up in the country southwest of Eugene- there can be some boring times for a youth in summer in the country and a boy naturally turns to the weather. So, I can say I’ve observed many hot summers and few more tepid. So, heatwaves have always been of special interest to me. First, as a geek I am profoundly excited by extremes, second our short heatwaves must have just the right set up to really boil us, and third…it still surprises me that it gets as hot as it does in the Willamette Valley a climate ruled so often by the cool winds of the Pacific with a high latitude. It can get really freakin hot.

The one most dramatic thing about this past summer- and just so you know meteorological summer is June/July/August- was how incredibly normal it was.Temperatures and precipitation really didn’t veer too far off.  Here are some facts: We had 14 days above 90ºF- exactly average. Our highest temperature (which occurred three separate times was 100ºF) again precisely our average highest temperature.  Rainfall, which we all know dwindles to meager amounts with these months  was 1.27″/normal 1.47″ for June. .66″/July normal .65″  and .09″/normal 1.57″ for August- was just about right on the nose. If you thought August was dry you were correct but it did not even fall into the 10 driest on record. It may just be that it culminated with that late heatwave the third week of the month. 99º, 100º, 100ºF in a row  sucked what little moisture was left from the surface and deeper soil horizons. .


Remember that we just came off one of the warmest winters of all time- for averages the warmest and a really warm and dry spring.  This past summer could have just followed the pattern that we’ve come to recognize as up, up,  up. (Last summer was technically the hottest ever with a record 29 days above 90ºF, a record number of days above 80ºF and the most overnight lows above 60ºF.) But the climate is made up of averages and as I’ve shown those for summer 2016 were well, average. Now just in time for your freaky Fox News loving, touched in the head, climate denier relative to chime in and remark that the numbers have been skewed to keep those greedy climatologists rolling in the dough. well, no they haven’t. The numbers which are dutifully recorded every six hours are right where everyone can see them on the Portland NOAA website. No one is hiding anything from anyone. Thats just bullshit. Thank you world wide web from the geekiest part of my heart.


But our gardens? What about our gardens? One of the things that mostly bamboozles me about our climate is how little people, even the weather service seems confused that we have wet summers? Even they are forever talking about rain chances in the future. But as long as I’ve been an Oregonian our summers have been dry. Bone dry. See above for our three summer month averages. They add up to exactly 3.69″ for three months. Thats EXACTLY what we average for the entire MONTH of October. Yep EXACTLY. Add high sun angle, repetitive bouts of hot weather sucking away soil moisture and you have one arid scene. In addition to that if you are an avid or even meek gardener you know that certain things can’t happen in our climate without some juicy intervention. And if some forgetful person decides to challenge me then I simply tell them to plant a vegetable garden in May and then NEVER water it. This isn’t the muggy, summer rainfall eastern United States- you know how that veggie plot would fare.  (Don’t get me started on planting trees in May-July without follow up irrigation, the attrition rate is horrendous).



Fall to early winter is forcecast to have above normal chances of average temperatures. The above map is for November/December/January- Courtesy PDX NOAA


As an aside you wonder why we have so many lush native trees? Well a good deal of them are actually summer drought tolerant. In fact a winter wet summer dry environment actually favors conifers which is one reason why they dominate the PNW. They are by and large much more efficient at preventing moisture loss.  And trees that are planted and become established have roots that follow the sinking subsoil moisture of the drying surface soil of spring into summer. The roots can reach far down- as far down and wide as the dimensions of the canopy above ground. The rain that falls onto the soil for the rest of the wet year sinks deeper and deeper and the roots of trees follow.

Now that we’ve recapped summer lets look at the future. You have to know that we are not headed for another El Nino or even a La Nina, nope 2016/17 will be a winter of No Nino. And that can mean several important things. First for the most part predictions favor a normal climate regime for our region in the coming months. And if you thought the last two winters were abnormally warm you were correct. Don’t expect that this winter- there are slightly elevated chances of an arctic outbreak in a No Nino- and it has provided some of our coldest episodes-And as the recent past has been mild a normal winter would average 2 days below 20ºF, personally we could and I say COULD experience our coldest weather since December 2013. I’m not just making that up. The averages point us in that direction. On average we get an arctic outbreak, a Phormium killer, an Agave melter once every three years. So you do the math. And as gardeners we should be nothing if not prepared.

So a normal winter is a distinct possibility but this year there is wrench in the forecast story. What 18 months ago was deemed ‘The Blob’ was an abnormally warm region of sea surface temperatures in the north Pacific. It had a profound effect on last summers scorching temperatures.  It dissipated for quite a few months but then voila’ its back-as of  late this summer. This could have a pronounced affect on our winter weather, what that is remains to be seen. Its not widely reported, but I’ve heard whispers that this isn’t actually a manifestation of global warming  but more likely a shift in what is known as the Pacific Decadal Oscillation. Thats when every 10+ years or so the Pacific Ocean pulls a switch and warm water collects to the north and cooler water goes elsewhere (South),  think of it as a much much longer duration El Nino event but instead of warm water flowing  east and collecting against South America, it moves north and gets caught in the North Pacific. This could do several things, it could re-orient the jet stream, it could funnel immense amounts of moisture to our doorstep, it could modify our temperatures or it could move to the west causing the jet stream to plunge north to south.  We’ll just have to wait and see.


Screen Shot 2016-08-17 at 10.09.03 PM.png


July 2016 Climate Report-

Link to the current climate report. PDX NOAA

So far NOAA hasn’t mentioned the Blob redux. Instead they show a very straight line right down the climatological center. Which jives perfectly with a No Nino year. If you would like to do your own climate research, I encourage you. All the information is right there on the ‘Climate Portal’ of the NOAA Wesite. If you don’t like numbers they even carefully color code the highest and lowest temperatures of the month. There you can find daily temperature records for select sites around western Oregon as well as temperature normals and rainfall records. Its not only handy for geeks its a great way for gardeners to either figure whats what or to compare the records in your own backyard. Here’s to a happy fall.









Summer 2016 and the blob redux

Make your garden sing!

Every garden is different. Of course that is obvious but there are certain aspects that really set apart exceptional spaces. Things that form a picture in your minds eye that you retain or you wish you could emulate in your own garden.  I talk gardens all day so I thought I would would share some tips on what makes them memorable.  These are my opinions and we have to remember that opinions are just that and they are not right or wrong. Consensus, however, congeals around repetition and I’ll address that in my choices. There are  certain things that make a garden sing.


It could be colors, it could be textures, it could be well placed beer cans, repetition is the soul of a garden. I say that because it actually does sooth the human soul. It imparts a sense of comfort by creating familiarity and  simultaneously creates the illusion of continuous smooth transitions. Our minds naturally create relationships. A seamless sense of transition is what really sets a garden apart. I’m talking about things that are easily controlled and easy to achieve. As an example pick a color any color that you love and put it here and there in your garden. It should match surrounding hues and it should be deliberate.  In my  own garden I’ve chosen several elements to repeat and it has caused me unbelievable joy.

My repetition of color is bold.

Build a consensus

In my back garden I have chosen to repeat the theme of the color chartreuse. Grasses, hedges, ground covers all combine for a simple cohesion. Sometimes its repeated distantly or it is interconnected.  Both ways I can then use this as a backdrop for tones or contrast favorable to that color. Blue flowers, yellow flowers, pink, purple all form focal points against this bright canvas.  You are not limited to color. You can repeat just about anything. Textures, patterns, even trees, shrubs, hedges as well as specific plants that appear in groups or solitary.  Most importantly, follow your passion. If you really, really, love something why not plant a whole sweep?  If there is a color that thrills you then by all means plant in a saturating mass. Sometimes, in this favored climate, our gardens can be repositories of one of everything. I call this the pawn shop look. Here, a little repetition can result in a more satisfying experience.

The Odd rule

One thing you might encounter down the garden path is what is known as the Rule of Three. That dictates that you always plant in groups of three.  This exists for several reasons and it isn’t to get you to buy more plants. The first explanation is that this mysteriously echoes the great natural patterns of the wild. Well, that may or may not be true- I’ve seen plenty of solitary  one off plants in the wild and I wouldn’t say the effect was wrong. The more believable scenario is that three (or more) creates the appearance of volume. As humans we react to more. It gets us excited.  Volume creates continuity where a single plant could appear lonely or simply disjunct.  You actually get better contrast in groups of plants because there is more to compare.  So when shopping for plants it seems that more satisfaction comes in groups of three and more. This rule is purely contingent on personal aesthetics but I’m surprised again and again where the results prove superior.

Deliberate action

A garden is by every definition a deliberate act. There is untold effort to make gardens appear natural. Well, thats deliberate too. So why not just go with it. I know from observations that people react most favorably to deliberate gardens. When a garden looks organized- even if it is planned disorganization that influence subconsciously interacts with your garden brain.   Look around you- sometimes you can force the aesthetic to deliver a better effect. Choose the high drama of large tropical plants OR plant one distinctive tree in a focal point- you have the power of influence. In my garden I have four boxwoods arranged in a line spaced equidistant. Right in the middle of the garden and it really does work.  It may seem superfluous but I know that it imparts structure and anchors the whole scene.

Hedges can be rigid or like this informal with just light pruning once a year.<Choisya x ‘Goldfingers’

Hedges have edges

Hedges are one thing that modern gardeners (in the PNW) shy away from. I’ve heard it all, too much work, too rigid, unnatural, well there is a reason people return from Europe besotted with ancient gardens. And its almost always a use of hedges. I’m not talking about anal retentively hewn boxwood chess pieces. I’m referring to plants that can deliberately be repeated in lines, crescents, curves  and then pruned either a lot or a little. As humans we seek control over nature- even if you yourself don’t picture it that way I’m here to tell you that primal fear of out of control things unnerves us. Hedges can be comforting then. One thing I’ve found by planting hedges is that the onerous task of pruning is not that big of a deal. My boxwood which I at first thought would lead to slavery actually only require one light pruning a year. And that is just to remove errant growth. Its important to consider that pruning is stunting. That is to say it forces a change in plant growth that lasts.  Boxwood react dramatically to just a light clip by branching like mad and becoming dense. Many, many shrubs do this. So an informal hedge can produce surprisingly uniform results;  try Choisya, Daphne, Myrica (Morella), Abelia,  with one or two yearly snips- and lightly at that. And the results can last a whole season if not into the next.  Take your time, use your gardeners eye of balance and nature- you control the shears. Remember that gardens are deliberate and the amount of influence you have over them is a choice not a sentence.

My back garden, an empty center, a focal point and layers of shrubs conceal the fence.


Take a cue from the theatre

Picture your garden as a stage. In theatre the stage is strictly controlled to impart mood, focus, and dramatic crescendo.  I’m not talking about getting a huge curtain- but think of the backdrop, the edges, even the mood, and lighting. You have complete control over this and it really is fun to see just how much you can manipulate your space. In my garden I’ve interrupted the view off of the center. A row of Crape Myrtles (‘Pecos) with multi-trunks is fronted by the four boxwood and underplanted with a continuous ground cover of shocking yellow ‘Angelina’ sedum. To the side it frames my lawn whose focal point from the view of the house is a large Albizia (Mimosa) ‘Summer Chocolate’. Around the outside of the garden I have layered shrubs and vines to block and eliminate views of a chainlink fence that surrounds the garden and which I was not able to remove. Framing a central section- creating a focal point and layering shrubs have all created a garden where I feel enclosed in my own personal space. From the neighbors aspect it is just a haze of trees and shrubs. As the seasons change the colors come and go and the sun angle shifts but the central elements remain the same. I’ve even introduced high quality solar powered spot lights to amp up the drama at night. In this play the gardener is the director.

A simpler task

Garden making represents a HUGE spectrum of results. Let your passion be your guide and accept some simple tips to create EXACTLY what you want. For those recently initiated the combination of plant culture, in concert with plant design can seem like an insolvable mystery. But time, experimentation even a determination to learn something new is certainly surmountable and you will find that your own knowledge of your garden will grow and once unthought of details will become familiar. Most of all trust your own sense of aesthetics. Don’t accept anything less than you expect and use a nursery of high quality to guide you in your decisions. Visit gardens for ideas. Garden with a buddy to bounce ideas and decrease the labor. Stick with your vision- and I guarantee you will never have a dull garden.






Make your garden sing!

Its that time of year. Garden etiquette.

I am more than blessed to live in a city of gardeners. In Portland it is not just a hobby its an overwhelming passion for many people. I know that just growing up in Oregon my plant vocabulary was enriched immensely by what surrounded me. In our fair burg one of the great traditions is open gardens. Owners sign up and pick a date and then let members of groups and the public through. There is nothing more educating and enriching than seeing how a gardener interprets the climate, their own special aesthetic, and personal collection of plants. I’ve been in the nursery business for nearly 27 years in this state and this rich tradition allows a true democratic sharing of ideas. But, there are some points that are imperative to those who visit gardens.

You’re opinion is nice- in your own head

One of the most bizarre things I’ve experienced is people walking through a garden and and actually speaking out loud as they experience a space. They throw off their own opinions in some sort of free associating ramble. “I don’t like blue”. ” I don’t like Roses” “That isn’t hardy”. Well I would like to remind people- even some very mature folks that visiting another person’s garden is time for us to use our inside our head voice. Remember that this is incredibly hard work and it is an art- that having been said you do not need to rattle off your opinions. Most importantly, no one cares, and second its very, very rude. (Questioning plant hardiness is a pet peeve, I can tell you that I’m pretty good at this subject and way more than once I’ve been proven wrong.) This person has extended themselves in a very personal manner. A painting is open to interpretation. Someone who has been on their hands and knees, hucking mulch, and preening what can be a VERY substantial area deserves the most polite behavior. Save it for the car.

Keep your hands to your self

When I first worked at a nursery a dear friend and colossally amazing gardener would open her space each Mother’s Day to the public. That was years ago and the theme was flowers- really, really, well grown flowers. On that Sunday at work I was shocked when after the tour a person came to the nursery where I worked holding a not so small branch of a flowering shrub. Not only did she demand identification, she balked when I asked her point blank where she got it. She told me, I asked if she had permission and when she stammered no, I was not very helpful. NEVER, NEVER do this. If you were invited to a persons house and you ripped a swatch of fabric off their furniture likely you would not be asked back. Its 2016, time to use technology. First ask the owner’s permission to take a photograph and then use your telephone to record whatever the owner allows. I’m positive that a smart nursery professional will be more than thrilled to assist you in this form of communication.

Don’t touch.

Ripping off a piece of a plant is a really dramatic example of bad garden etiquette, but there are several other things that you should employ when visiting someone else’s personal space. Don’t touch.-No matter how obsessive you may be in your own garden that does not give you license to interfere. One of the worst things you can do on a garden tour is either point out or actually pull a weed. Don’t do this. Again, if someone came to your home and started dusting I’m pretty sure you would be pissed off. Every garden has a scale that the person is seeking to control. Some are informal and some are very precise, that doesn’t mean you should point out what you consider are errors. Instead, consider what the gardener is thinking , what they are trying to accomplish, appreciate each garden style and scale for what it is. Informal, formal, personal, wild. There are infinite categories of this medium. Open your brain to this.

Identity. Patience and polite

You most likely will encounter plants that are unfamiliar to you. Once again, this is a very complex subject in our town. And, people may use plants differently to achieve a certain effect. This combination of culture and design can confuse even the experts. First, ask the owner politely for the identity. Don’t be upset if even they don’t rattle off the name for you. There can be thousands of plants in a garden and some may know, some may not immediately. There may even be a tag hiding somewhere in the duff. Do NOT go  for it your self. Personal space. The owner may volunteer to search for the tag, crawling around someones garden is bad behavior. Sometimes its a mystery. No badgering the gardener. Leave it at that. Again, ask politely to take a picture- the owner may know where they got it- here, you can be a savvy investigator- do your own work. Technology is your friend.

Secret Spot

A few other tips

Botanical latin is a tricky business. We all know that its primary function is to refer exactly to a certain plant. Common names are often useless because they can be repetitive and even vague. The utmost important thing is that both you and owner of the garden realize that not every one has the same plant acumen. For example, as a nursery owner and plant sales person I have to constantly remind myself of this. One way that I have approached this this is to go into a bicycle shop in Portland. I know NOTHING about bikes and I’m completely intimidated by the subject- exposing myself to that reminds me exactly of how customers feel when people begin rattling off latin. So don’t expect people to know as much as you.  And as a garden owner, professional, or visitor- you must resist the urge to correct a persons pronunciation. Unless, it is hopelessly wrong and this prevents identification or if the person is struggling to pronounce it. Bikes, numismatics, physics- think of anything that has intimidated you- that is likely how the novice feels. You can be quiet or you can be gentle just don’t be an ass.

Visit gardens- there’s really nothing like it.

So- in this season of garden visits there is nothing more fun, more enriching than visiting another persons space. Take a moment to collect yourself, use your best behavior, appreciate what you see, how it is interpreted and above all consider the amount of work that has gone into garden making. There are so many styles and rich collections of plants you are bound to learn something that you didn’t already know. Don’t pick out errors, don’t shout out loud how much something costs. Personal control is key. Remember that it is 2016 and we all carry around not only the most powerful tools for research in our pockets but the means to visually record. Ask permission. Stay on the path and most of all point out to the owner of the open garden at least one thing that you liked. Because if you have nothing good to say just please fake it.


Its that time of year. Garden etiquette.

Native plants, strip clubs, and diversity.

Familiar orientation north to south

Years ago Greg and I were driving up to his father’s cabin in the mountains of eastern Humboldt county California. Its located at 4700′ elevation on Horse Mountain in the higher ridges of the Northern Coast Range. As we wound up the mountain on a scary one lane road a familiar feeling over came me. At about 3500′ the composition of the flora changed and I was stunned. The forest was primarily composed of Douglas Fir (Pseudotsuga menziesii), White Oak (Quercus garryana) and California Black Oak (Quercus kellogii). Interspersed occasionally were Ponderosa pine  and Western Dogwood, and the understory was familiar Amelanchier (Serviceberry) and Western Viburnum (Viburnum occidentalis). It struck me because that was nearly the exact composition of forest that I grew up in SW of Eugene in Western Oregon. That was at 500′ elevation but here 375 miles to the south it had shifted according to the climate at 3500′. This shows how our native plants orient themselves according to elevation from north to south. Half of Southern Oregon is clearly in the California Floristic Provence and that same composition of plants (with the inclusion of others) can be found higher and higher as you move south. The same zone can be located in the middle and then higher elevations of the Sierra Nevada inland.

Plants Migrate

You of course are familiar with the migration of animals. Did you know that plants migrate too? In college I studied this movement according to the changing climate from the ice ages to the interstadial warm period (between the ice ages) and then back as cooling took hold again. You can re-create the climate by collecting the mud of lake bottoms, washing it and isolating the pollen. The remains  are un-decomposed in the anaerobic conditions  with the specific characteristic of each species retained. You can then carbon date the pollen and reconstruct the taxa assemblage (plant composition) and relate that to an existing analog and recreate a picture of a past climate. For instance during the height of the ice age 11,000 years ago the Willamette Valley was very different. Pollen shows that the predominant trees were Picea englemanii , (Engelmann’s Spruce), Tsuga mertensiana (Mountain Hemlock) , Pinus contorta (Lodgepole Pine) and Aspen. Currently that assemblage is located just to the drier east of the Cascade crest at approximately 4500′. The climate was not just much, much colder it was drier as well. I won’t go into the weather /climate that accounted for that but suffice it to say things were quite different from today.  As the climate warmed the plants changed and followed. Low elevations species surged north and up and higher, colder adapted species were relegated to the higher elevations.  Up until 3000 years ago we had been (HAVE) been getting cooler going into another cold period and flora was beginning to switch its migration. We all know now that we have changed things and things WILL be drastically different in the next few hundred years.

Trillium kuraybayashii
Exquisite Trillium kurabayashii

We’ve gotten in the way

If humans hadn’t interfered- and gotten our big ass selves in the way the climate and plants would have adjusted and moved according to a much slower pace. Temperature changes of 1ºC per thousand years gives plants some time to reorient. Now we are looking at 3-5ºC warming in the next 60 years. That far outpaces the natural progression of plants and not to mention we are in the way cutting off corridors of migration. Dentist offices, farming, strip clubs are all in the way. So, without giving a bigger guilt trip I prefer to look at things in a more pragmatic way. Our native plants need our help. There’s no way they can adjust to the time frame we’ve thrust upon them and the results could be disastrous.

Diversity is the issue

So, we have national parks you say? Well yes but the climate will change and the plants will not have a reasonable amount of time let alone a corridor to move. This is where we need to step in. There are a select few species that have already been used – repeatedly, over and over again in our landscapes. Natives that make people feel good about spouting off sound bites that they  are using “native plants”. And this makes everyone feel better. What has happened is two fold. First the easiest to grow and most adaptable natives have come to dominate the field and what we have now is a great lack of diversity. Native plant ghettos as I call them. Where once in a particular location there was the diversity of scores of species now – for instance in the parking lot at Target there are four native species represented. What are they? Well, usually Ribes sanguineum, (Flowering Currant), Cornus sericea (Red twig Dogwood) Myrica californica (Pacific Waxmyrtle) and the most abused Mahonia aquifolium our ubiquitous state flower.  The plants may be native but diversity is slashed. Native annuals, perennials, shrubs, trees …..all eliminated for three or four species and it makes people feel good. If we want to maintain our native diversity this is going to have to change.

The hills are alive

So at Xera we have chosen not to exclude those few repeated species- there is absolutely nothing wrong with them but we’ve engaged on a path of the details that are getting left behind. We want to reconstruct the diversity that was present before  settlement and we want to expand peoples ideas about how plants move and need our help. And- as a gardener you have never been to visit our amazing native plants in the wild you are missing a great deal of the enjoyment of gardening. Much like viewing animals on a safari there is a great joy in viewing our native plants in their habitat. Not only does it swell your appreciation for beauty it teaches you to view the whole picture. Combinations, soils, aspects, all come in to play and can give us great ideas about how to construct plant communities in our own gardens. And though there is a great vogue for the latest plant from Taiwan or Szechuan I can tell you that we have thousands of our own  native treasures that should be discovered as garden plants and they need our help.

Its the details

We already have a climate that supports an immense wealth of diversity but we need to be stewards and use these plants as they are adapted. One thing that must happen to establish a native community is to protect those plants from invasive exotics that overwhelm and stress our native composition. Next, we need to adapt our aesthetics as gardeners to the natural ebb and flow of wildflowers and seasonal interest. Then, we must provide these protected communities with the little bit of care to protect them. And its not that hard. They are already adapted to our soils and rainfall patterns. Inclusion in our gardens is just one way to ensure that they live on and that diversity is preserved.

Vancouveria chrysantha
Vancouveria  chrysantha- Yellow Inside Out Flower is a fantastic native perennial for dry shade

Let the sun shine in

So, take a little time  to go out and visit our native plants. And its not a trek either -less than two hours into the Gorge in June sees hillsides replete in blue Ceanothus,  with pink nootka Roses and the penetrating perfume of Philadelphus (Mock Orange).  Underneath are wildflowers such as Alliums, Sidalceas, Lomatias, even nifty native clovers that make enchanting garden plants. Thats just one of a number of places that deserve a visit. Saddle Mountain in the Coast Range,  The Rough and Ready Botanical Wayside in the Illinois Valley of Southern Oregon. Visit and come away with some of the best garden ideas that are applicable to our climate and region. These plants are going to need our help. We must honor them and diversity. As gardeners its our job.


Native plants, strip clubs, and diversity.

Climate Change- Portland of the Future

I’ve gone through past records and given a summary of the changes that our climate has undergone in the past. I thought it might be fun to go through with a mock summary of what our climate could look like in the future. In the past 100 years Portland has warmed by approximately 1.5ºF. I’ve found that this has had an affect on our climate averages based on a compilation of extreme temperatures and their averages. In the past 60 years Portland Airport has moved from Zone 8a (15ºF) to near zone 8b/9a (20.3ºF).

The past shows us the future

In college when I studied climatology I learned some very important ideas about how you characterize the climate of the past. You actually look at the composition of flora and then reconstruct the climate based on the modern analog of plant distribution. For instance pollen records are found from the anaerobic mud of lakes (there pollen is preserved and does not decompose for thousands of years without oxygen) , carbon dated then re-constructing the flora at the time and comparing it to modern analog plant distribution. You can tell an awful lot about the climate by the native ranges of plants.  For example you can summarize our climate from the height of the last Ice Age approximately 10,000 years ago (much colder and drier- likely akin to east of the Cascade Crest at 4000′ ) and then through what is known as the interstadial (a period of warmer weather peaking 6000 years ago) and then to the present. Until the specter of global warming we were actually headed back into an ice age and long term temperatures were on the slide.

The climate is always changing

Studies of past climate perturbations show that there has been a very complex set of influences on climate. Solar activity, ocean currents, CO2 levels and more factors must be combined to get a clear picture. What this means is that some parts of the globe change their climate at different times. It does not all heat and cool like a cup of coffee in a microwave. Things dip and sway, heat and cool and this elegant dance is what drives global climate shifts. Overall, climate change on a global scale requires changes on a global scale. Global warming- greenhouse gasses is as profound a global influence as has ever occurred in the history of humans on our planet. That does not mean that we haven’t endured climate change in recent human history. The Little Ice Age (1350-1910) is one such switch which had a profound effect on humanity. Driven by a low in sunspot activity (The Maunder Minimum) – a lowering of solar insolation (the sun’s heat output) combined with enormous volcanic eruptions which pumped gasses and material to block the sun, this period of much colder weather caused winters in the Northern hemisphere to plunge and glaciers advanced. And all of this was just 1ºC lower than current levels. In Europe the cold had a profound effect. It has been tied to everything from famine to the outbreak of disease.  A good way to remember the influence of the Little Ice Age is its depiction in the art and literature of Europe at that time. Ice skating was common on canals in The Netherlands, in England Dickens idealized winters of snow and cold, in fact the very idea of a white Christmas originates from this time.

South Moves North

During the interstadial warm period several things happened that will likely be pertinent to our immediate future. For instance, this warmer period also saw the duration of summer drought expand in Western Oregon. What this means is that it favored drought adapted species. Oak and Ponderosa both expanded their range at the expense of more water loving species. In southern Oregon where there still occurs the hybrid oak the Mohr Oak (Quercus wislezenii x Quercus kellogii) we know that Quercus

Native plants will require our assistance

wislezenii – California Interior Live Oak- whose range now is exclusively Californian must have occurred in Oregon for that hybrid to be present as it is still. Most likely the Willamette Valley  of that period had the climate and plant communities now found 250 miles to the south in the Rogue River Valley.  Portland, you were Medford. Hotter and drier for a longer annual period.

Super compressed climate change

Even the Little Ice Age occurred over a period of centuries (with dips that manifested in decades) but the temperature overall fell just 1ºC over that time period. What if you ramped up the change and compressed it into just a few decades? Well, even if you stopped the input of all carbon into the atmosphere tomorrow what we’ve already contributed has set us on an unstoppable path of warming. According to the U.S. Fish and Wildlife warming will continue and actually INCREASE through the rest of this century and beyond.   Conservative estimates are that we will rise 2ºF in the 2020’s, 3.2º+F by 2040 and a whopping 5.3º+F by 2080. (Remember we’ve increased just 1.5ºF in the last 100 years.). What effect this will have on native plants has yet to be realistically described as far as I can tell. Species that are in the most finely balanced biomes are likely to fail and plants with greater adaptation to enhanced summer drought and longer growing seasons will likely persevere. Remember that great shifts in climate in the past offered plants plenty of time and un-human obstructed paths to move. But what about our gardens? Increased length of summer drought, longer growing seasons, much higher winter and summer temperatures all will have a profound effect.

A modern analog to Portland’s future climate

I looked carefully at the weather records of cities on the west coast to surmise a future for our gardening climate.  Location and climate is influenced just as much by local conditions (topography, latitude, ocean influences) so there will not be an exact analog ever. Instead my study of weather records showed some more general descriptions and I have to say that what I came up with is much more of an educated guess than purely scientific. If as during the interstadial warming period the climate appeared to have shifted north it was my estimate to look to our south for a glimpse at our future. And remember that we are not only at a higher latitude but we are closer to sources of arctic air as well. This also does not take into account annual precipitation which is slated to stay the same or increase. I focused primarily on temperature averages.

Welcome to…….

Santa Rosa, California- Portland, 2060. Yep. After poring over records and tying them to our projected temperature increase this one location stood out above the rest. You have to know a little about our climate to understand why we will evolve close to this. One is proximity to the ocean and marine influence. Santa Rosa is closer but we have just about the same amount of modifying ocean influence- this holds down both their and our summer time highs. Santa Rosa is also drier than we are (but not by much 32.28″ for them, and 35+” for Portland). So, I compared overall average temperature as well as days above 90ºF as well as days below freezing and Santa Rosa kept popping up on the list. This is based on the rate of increase given by experts. In 2060 our climate will have undergone a striking change and I surmise what we grow in our gardens will have as well.

Portland vs. Santa Rosa

With a projected annual increase in temperature of 4ºF by 2060 there will be stark differences from today and even more stark differences in what we can grow. For instance, Santa Rosa of today experiences 30.2 days below freezing- compared to Portland’s current 44 days. 28.9 days in Santa Rosa rise above 90ºF (Portland’s current average is 14- and remember last year broke the record for the most days-29).  Portland’s winter time temperatures will increase dramatically. From an average high in January of 47ºF we could see the mid 50’s.  So what will grow here? I anticipate a lot more Palms. Heh. We will be squarely zone 9 by that time. Many more Australian plants as well as possibly even subtropical plants. We will have a much longer period of summer drought. Water use will have to become much more responsible.

Climate Change and our Responsibility

Plants are adaptable but the pressure we are going to place on native plants means that we should be stewards above all else to ensure their survival. Gardeners are adaptable and I have absolutely all the faith that our gardens will be just fine. Most of all we have to pay attention, learn, and adapt with our rapidly changing climate.



Climate Change- Portland of the Future

The Facts in a Changing Climate

I recently did a talk at the Yard, Garden, and Patio Show in Portland, entitled ‘Plants for a Changing Climate’.  Some shared interest that I post my talk so I will describe it in this blog and I hope you find it informative. The first half of the talk was describing the weather over the past 60 years. The second half was plants. I’ll just be talking about the weather here. I’ll try to keep it as cut and dried as possible- I won’t veer off though I have a habit of that. Heh.

The Record

There are many ways to approach the climate over time. And I won’t bore you with intricacies but I will show how I arrived at my information. To be simple and precise I chose to compare our extreme temperatures as a way of showing change.  I won’t be focusing on monthly averages or even yearly day to day averages. To make it more comparable, this is how the USDA arrives at their zones so it seemed appropriate. The weather record in Portland is not exactly as long as you would think so I used two records to make up for that. The official record at Portland International Airport only extends as far back as October, 1940. Thats when the airport was moved from Swan Island to its current location. Why there isn’t a published record on Swan Island, I don’t really know, but I have seen it mentioned in old literature. The second record which extends back to 1875 is that of downtown Portland. I’ll talk about why that is useful but also limited. Be aware that these two records are urban- well not as much the airport but they are our official records and there is quite a bit of difference between them and the suburbs. I’ll also review the distinct microclimates in the metro area.

Screen Shot 2016-02-10 at 8.20.19 PM

20ºF, 100ºF- Life above and below

In my search through records I had to delineate certain temperatures to make it more simple. For instance, I chose 20º above (zone 9) and 20ºF and below (zone 8 and colder) and that was fortuitous. Think of zone 8 as the line we cross into what we consider arctic air in our region. It turns out that is exactly how our winters fall, to give away a simple fact our average annual low at the Portland Airport in the last 30 years is 20.3ºF (-6.9ºC). And our winters have a distinct percentage above and below that line. This is arbitrary, I know but it really works for our discussion. Also, I reviewed our annual highest temperature and would you believe that is exactly 100.0ºF for the past thirty years? Tracking the ultimate high might mean less to gardeners than freezing temperatures, but I wanted to see if that foretold a trend in extremes as well.

30 Year average

The official USDA zone maps are compiled by averaging the yearly low temperature extremes at official reporting stations. This is done in 30 year increments and the last thirty year review was 1980-2010. In my review I chose to look at 1986 to 2015 in order to see if there had been any more change in a more modern appraisal. The information is there so, hell, why not? The official temperatures at official reporting stations are compiled and then isothermic lines are drawn to delineate the zones in the region. For instance, in the Portland Metro area those official reporting stations are: Pearson Airport- Vancouver, Scappoose Airfield, Hillsboro Airport, Portland International Airport, Troutdale Airport and Aurora Regional Airport. Those 6 stations are relevant to our immediate area. By the way if you look at our current observations page at the NOAA website those are what come up and those are the only stations with official records. Of course there is a significant amount of difference between each station. Topography, elevation, exposure to the Columbia River Gorge and distance from it all play into the local climate.

Microclimates: Macro differences

Microclimates in our region are distinct in several different ways. First, elevation has several effects. You might think that the higher you are the colder you are, well thats only partially true. Honestly, cold air sinks and the most extreme cold temperatures in our area are recorded at the lowest elevations. Once you get above about 700′ the temperature again begins to drop. So, slopes between 700′ and about 200′ in the metro area (and Willamette Valley) are considered thermal belts. If thats difficult to picture just remember that is where you see wine grapes grown in our region- there they avoid late and early valley frosts and the cold air sweeps downhill and does not collect. The most important aspect of elevation in western Oregon is that the higher you are the wetter you are. Elevation is the key. The Portland Airport at 21′ above sea level records the least amount of rain in the metro area at 35.10″ annually. In the west hills of Portland above 800′ that average spikes up to 55″ and more. As far as precipitation is considered elevation is everything. By the way downtown Portland at 110′ elevation averages 42.30″- so you can see how sensitive that is. A few feet and wow. Also, there is much more snow at higher elevations and this increases even more dramatically.


The longest records and what they tell us

The longest record of Downtown Portland- taken at the KGW Television Station currently tells us a lot about the trajectory of our climate. Computing the averages 30 years at a time from 1875 until 1955 and guess what? Our climate was colder. There were warm years and very cold years.  What is interesting about this time frame is two striking things. First the 19th Century was very much colder than the 20th century- we were exiting the Little Ice Age which ended in approximately 1910- most likely that was caused by what is known as the Maunder Minimum a period of less sun spot activity and some pretty honking big volcanic eruptions (Tambora 1815) contributed to significant cooling. Then in the late 18th Century the industrial revolution began spewing CO2 into the atmosphere and sun spot activity changed. A combination of the two shows a turn in climate. And you can see a change. An example that shows warming sensitivity is average annual snowfall. In 1900 downtown Portland averaged 18.1″ of snow per year. Thats an awful lot. Currently, we only total an average of 3.1″.  Also, there were regularly widespread regional arctic outbreaks that lasted for weeks at a time. In fact the Columbia River and the Willamette both froze over regularly. That speaks not just of intensity but duration of freezes. The last record of both rivers freezing completely is 1933. Also, exceeding 100ºF, rare in the 19th Century became much more frequent following 1910. This is a trend that has repeated all over the west so we know some sort of transition was taking place. Just for fun there was only one year that never dropped below freezing, that was 1934- and as you know from history the 1930’s showed great perturbation in climate- not just the dust bowl but in the PNW as well.

The Ultimate Extremes

I chose the last two thirty year increments to really delve into details. And before that just how cold was it? Downtown Portland’s coldest temperature officially was -2ºF in January 1888- a month that saw more than three feet of snow- something unfathomable now. At the Portland Airport the coldest temperature was -3ºF in early February 1950- a winter of intense cold and and snow. In an aside the coldest temperature recorded that winter  night in downtown Portland was a relatively warm 7ºF- remember microclimates are everything. It could be that by that time the urban heat island was beginning to emerge. The urban heat island is just that- an area like an island in urban cores where glass and asphalt absorb heat and then release it gradually.  It becomes very apparent in averages.  Surprisingly the warmest temperature prior to 1955 downtown was 107ºF in 1942 a high that hasn’t been achieved since.

1956-2015- Downtown Colder then…

To really get a handle on our climate I chose the last two 30 year increments to see if that showed valuable change. I figured the last 60 years is about relevant to the older plants in gardens (heh). And what I discovered was not a huge surprise. In 1956 to 85, downtown Portland had an average annual low of 19.3ºF- Zone 8b. There was just one winter below 10ºF (Zone 7) 6ºF in 1968. 13/30 winters were Zone 8 or colder and that averages out to 43.33% in that time frame. Conversely, 17/30 winters were above 20ºF- or 56.66%. Now, this is in the urban core so it is only surprising in that it is way warmer than most people would surmise. The warmest winter was the El Nino year of 1958 where the lowest temperature was a paltry 31ºF. Barely a frost. The average annual high was 99ºF with an ultimate high of 106ºF in the great heatwave of August 1981.  In 1985 to the present the downtown recording station showed slight warming. In that time the average annual low rose to 22.3ºF (Zone 9a) and zone 9 winters increased slightly to 60% of average. The highest temperature remained stagnant and the highest recorded temperature was 105ºF in July, 2009.

1956-2015  Volatile weather at the Airport

The average low temperature at PDX in period 1956-85 was exactly 15ºF (Zone 8a). There were 21/30 years in those 30 years with winters zone 8 or colder. (70% of winters). Five of those winters were zone 7 (10ºF) or colder with ultimate lows of 6ºF in 1957 and 1964. Just 9 winters were zone 9. What is striking is that in the last 30 years the percentages have reversed. Fully, 56.66% (17/30) winters were were zone 9. and just 43.33% of winters of zone 8 or colder. The most striking statistic is that the coldest and last official zone 7 freeze at PDX was February, 1989 with a low of 9ºF (a particularly brutal freeze with highs in the teens for 3 days). Thats 27(!) years since a true zone 7 winter.  Something has changed. Nothing like that expanse of time shows up anywhere in the previous records. The highest temperature was 107ºF in 1965 and again during the phenomenal heat wave of August 1981 where 107ºF occurred twice in one week. So, the average annual low- as I said rose to the current 20.3ºF (Zone 8b)- unless you want to believe we are .3ºF into zone 9. The warmest winters were 1999 and 2002 and where the lowest temperature was just 26ºF.  (This year the lowest was 24ºF and last year it was 23ºF).

Microclimates show much greater extremes.

Those are urban records and I took a look at the records from the other reporting stations and they show quite a bit of difference. In Hillsboro for instance the coldest temperature of 4ºF was achieved in 1989, 1998 and it dropped to 7ºF as recently as December, 2013. Cold air sinks and away from the Columbia Gorge in the Tualatin Valley where there is less air mixing and greater radiational cooling as well, it gets quite a bit colder. This pushes Hillsboro down to Zone 8a (11ºF) and it averages a zone 7 freeze at least twice every ten years.   Another surprisingly cold part of the metro area is Vancouver as well as rural Clark County. Cold air collects and in 2013 the mercury dropped to 7ºF in the last big freeze. This area though officially zone 8a (14ºF) averages one out of ten years with a zone 7 freeze. In both of these locations that should be taken into account when choosing longer lived plants (shrubs, trees).

Our current climate

So, what is our climate like in the 21st Century? And remember that averages are made up of extremes. There will be colder winters as well as warmer winters- that is part of climate. The way it affects gardens is real. And you should always record the temperatures in your own garden- you may live in a frost pocket. Remember that exposure to subfreezing winds (from the Gorge) knocks off a lot of plant hardiness. I like to remember that at 20ºF a 30mph wind causes the equivalent damage to a wind-free 10ºF- thats how zone 8 plants can be damaged or killed at a zone 9 temperature. And gardeners here know that sodden plants can be injured in combination with low temperatures. We can expect one day a year with a high temperature below 32ºF. One day a year with a low below 20ºF, 44 days below freezing, one day a year with a high above 100ºF and 16 days above 90ºF.

The future looks very different

In the last 100 years our temperature in the PNW has risen by 1.3ºC. And you can see that has had a distinct effect. We will continue to warm. 2015 was our warmest year ever, we broke the record for most days above 90ºF (29) most days with highs above 80ºF and most lows above 60ºF, 6 of the 12 months were the warmest on average ever recorded. And the number 2 year? 2014. Its a trend- last year was a glimpse into the future. Experts expect that our climate will warm in the PNW by 3-5ºC by the year 2060. Thats kind of hard to imagine. Snowpack will become more volatile, low elevation snow will likely disappear and water will take on more importance. More than ever we should learn about our climate and prepare.












The Facts in a Changing Climate