Zoning out in Portland

A grasp of Zones in Portland

Everybody who gardens has at least a rudimentary grasp on the USDA climate zones. At our nursery I will often hear someone shout out that we are Zone 7 and yet the USDA map clearly shows Portland in Zone 8b. Which is correct?  Well, both technically. I know that is confusing but I’ll explain the USDA Zones what they mean, how to interpret them, how I interpret them when choosing and describing plants for garden success.

Context and zones:

0º to 5ºF     Zone 7a

5º to 10ºF   Zone 7b- Portland’s coldest winter of the past 30 years. (9ºF February 5, 1989)

10º to 15ºF Zone 8a

15º to 20ºF Zone 8b

20º to 25ºF Zone 9a

25º to 30ºF- Zone 9b Portland’s mildest winter of the past 30 years. (26ºF, 2002)

Hook yourself up with a weather station

Kissed by the Pacific

We are extremely lucky to garden in Western Oregon, its a benign climate with certain factors built in that leads to success with an amazing palette of plants. What makes this possible, abundant winter rainfall, dry summers, sufficient winter cold and abundant summer heat- all of these factors mimic climates from around the world. Perhaps our greatest attribute is lack of real winter cold. Arctic intrusions are brief and the moderating effects of the huge Pacific Ocean impacts our climate more than 80% of the time- we are literally kissed by the warm winds of the Pacific. Just as important the Cascade crest blocks arctic air from frequently intruding to the west and the east trending jet stream sweeps the coldest air predominantly to the lee of the mountains.  All of this and we are at the same latitude as Minneapolis but escape any real arctic nightmares.

Get your weather geek on

This may be geeky but its incumbent upon the gardener to have a certain grasp of the details of their climate. Zones, I see you zoning out – stick with me, I will attempt a summary of our climate as a refresher and I’ll show you what USDA zones really mean as well as the finer points. For instance I garden in the city of Portland. Officially, this is USDA Zone 8b. That means that official reporting stations in the city average their coldest overnight lows over the past 30 years and come up with an AVERAGE annual low between 15º to 20ºF (-9ºC to -7ºC). To be more precise our average annual winter lowest temperature is 19.7ºF(-7.5ºC) at the Portland Airport. Wait a minute you say, I have been colder than 19ºF in the last 30 years. Yep, its an average and averages are made up of extremes. In the past 30 years we have been as cold as 9ºF and have had winters where the ultimate low was a balmy 26ºF. So, how do I use the USDA climate zone to garden?

In the zone

At Xera we use the USDA zone designations in a different way. When we grow a plant we take into account the coldest temperatures in the past 10 years. (11ºF).  All plants have a lifespan and for instance, if you were to plant a shrub or a tree with a very long lifespan you would be in danger if you relied on the average lowest temperature- in a ten year period you would expect colder temperatures, which could lead to severe damage to death. So we use the framework of the USDA zones- the 5ºF increments but we adapt that to our climate. For example our arctic events are very short lived and have several components that I factor in. During our coldest events which occur every three years or so we not only experience cold overnight lows- but true arctic air makes subfreezing high temperatures occur as well. This adds stress to a plant and has to be factored in to the equation.

Australia offers up an example

One of the best examples of specific climate adaptation comes from many Australian plants. Alpine plants from Australia can be grown very successfully in our climate. And ultimate lows there are comparable to ours. But, Australia, though it can get cold, has no real source of unmodified continental arctic air as we do. There elevation plays a much more important role in the coldest temperatures. And even that is misleading as their very highest elevations pale in comparison to ours. Remember that cold air sinks and it is in mountain valleys in the Australian Alps that you find the ultimate coldest temperatures. And the coldest ever recorded is just -9ºF for the WHOLE continent. Compare that to Portland’s ultimate lowest -3ºF (February 2, 1950) and even the coldest ever recorded in Oregon which was an insane -54ºF in the Bear Valley at Seneca in Eastern Oregon. In Australia very cold overnight lows are often followed by fairly mild- above freezing high temperatures. This wide diurnal stretch allows plants to recover daily from some pretty bitter night time temperatures. As I said when arctic conditions occur here we can expect some very cold high temperatures- in the 20’s for at least several days. Thats the difference between us and Alpine regions of Australia. So a plant there might be zoned as 8a and survive 12ºF but daytime highs mitigate the exposure. Here it may survive 12ºF lows but succumb to daytime highs that don’t budge above freezing. It is one of the reasons alpine Aussie Acacias should work here but don’t. This large diurnal temperature pattern is also common in inland California as well as parts of the southwest.

Freeze the hell out of that plant

The trick then is to find plants that can handle our 10 year coldest temperatures as well as the inevitable subfreezing highs that accompany an arctic outbreak. And- each freeze is different (duration, depth, wind, snow cover) So how to come up with a hardiness rating? Observation over many years, provenence (a plants specific native origin- including elevation and latitude) and testing plants. For Xera that means we’ve killed a lot of prospective plants in order that they do not die an untimely death in your garden. And even all of that does not mean that a plant is full proof. As you know wind can have a MUCH greater element of stress to a plant. Our arctic events almost always are accompanied by arctic ouflow from the Columbia Gorge. Portland has a unique orientation to the powerful winds that roar from the much, much potentially colder source of air that is the Columbia Basin. In my best estimation of gardening here for 35 years I can say that observation of wind- precisely SUB-freezing wind, leads to a profound effect on cold hardiness.  For example, a temperatures of 28ºF and a persistent 25 mph wind can cause the same affects as a calm 18ºF. Thats 10ºF of cold adaptation that must be factored in as well. This is how plants can die even though we haven’t technically achieved their coldest tolerance (in calm air) and they are rated for much lower.

Hardening off

Ideally you would like the temperature in Fall and early Winter to become steadily colder exposing plants and naturally hardening them off. I welcome light freezes in November and December that naturally prepare plants for possible colder temperatures later on. And almost all somewhat hardy plants can be affected by this- even surprising plants such as Phormium benefit from gradually cooling temperatures. Unfortunately, that is almost never the case. Arctic outbreaks can come rushing in following mild temperatures and this can wreak havoc on the garden. So, I also factor in that element as much as I can.

Achieve the ultimate

In order for a plant to achieve its ultimate tolerance of cold it must be grown in the most optimal conditions. Make certain that if a plant requires full (all day) sun that it receives it. An example of this is Callistemon (Bottlebrush) which can be significantly more tender to cold in shaded locations- it really requires exposure to harden off. Establishment is a very potent factor- the older and more established a plant the hardier it will be to cold temperatures.  A bold example of this is Fringebush (Loropetalum) small new plants succumb to 20ºF and established large specimens roll through 0ºF with no problem. Its important that if a plant is borderline hardy Zone 9a or even Zone 8 that you plant it no later than May 15- that allows it to maximize establishment with the longest growing season possible. Agaves are another case in point.  If they have put down a taproot in a long growing season they are many, many zones hardier to cold than when not. Greater summer heat also creates cold hardier woody plants as well and luckily we have just enough days above 90ºF for this to be a benefit.

Sodden and frozen

Our heavy winter rainfall can also have an adverse affect on cold hardiness. Sodden soils do several things to plants in combination with severe cold. Wet soils mean that a plant is full of water- thus restraining dormancy and when jack frost hits- it results in injury or death even at temperatures much warmer than a plants native haunts. Cold and dry- well drained conditions that many plants are adapted is a much better state of things. Many southwest natives such as woody Salvias, Agastaches, Yuccas, Cacti and Agaves can take incredible cold if they are in dry conditions. Even alpine South African succulents- ice plants (Delosperma) sail through winter in places like Denver- exposed to temperatures well below zero for many weeks but in dry conditions. In western Oregon Delosperma either freezes out at wet and 20ºF or is seriously compromised. These plants cannot tolerate the lack of oxygen in the soil that sodden frozen conditions create. If a plant calls for good drainage, amend the soil with non-organic material, plant it on a slope and do not cut back the frosted foliage until all danger of freezing conditions have passed- usually mid-April. The rainfall averages vary greatly over the city of Portland and this often shocks gardeners who find that from a low of 37.5” at PDX which is at sea level to more than 65” annually in the West Hills above 700’+. Thats a huge difference in just a few miles. In western Oregon its all about elevation. Not just because of snow levels but influencing overall precipitation accumulation as well- the higher you are the wetter you are.

Outlying regions are colder

I’ve been discussing Portland but its important to know that areas away from the city are quite a bit colder. Hillsboro, Vancouver, and Salem are generally a half to a whole zone colder. So look for plants that are hardier for those locations. The urban heat island is not only apparent in Portland it appears that it is having a much more profound effect on our gardens. In those locations take advantage of favored microclimates if you are unsure of a plants cold hardiness. That is south facing aspects, at the top of a slope or adjacent to asphalt or concrete. Also, many slightly tender plants benefit from the over head protection of a tree canopy.

Your own garden climate

So you can see how we can be considered both Zone 8b (annual) and Zone 7 (30 year stretch) and the many factors that play in to cold hardiness in plants. It is great to set up your own thermometer and get to know the intimate climate in your own garden. Microclimates can really vary between reporting sites and everything from amount of asphalt in your neighborhood to elevation can play an important part. If not the National Weather Service has a wide web of reporting stations and its not difficult to locate the closest to your garden on the observations page of their excellent website. Get to know your own zone and improve your gardening acumen. There are more complex factors than just a simple low temperature.      -Paul

Portland/Vancouver Metro Weather Recording sites:


Portland weather: Fun Facts

Portland’s coldest temperature was -3ºF on February 2, 1950.

Portland’s warmest and only frost free winter was 1934/35

Portland’s average lowest temperature (at PDX ) is 19.7ºF USDA Zone 8b

Portland averages 2 days per year with subfreezing high temperatures

Portland averages 33 days a year below 32ºF  (Ave. Freeze date Nov. 20 to March 19.)

Portland’s coldest high temperature ever 14ºF January 1968

Portland’s highest temperature ever is 107ºF in 1965 and twice in one week in August 1981.

Portland’s warmest overnight low was 74ºF on July 30, 2008.

Portland averages one day above 100ºF per year (101.3ºF) and 14 days above 90ºF

Portland’s most days in a year above 90ºF was 2015 with 29 days.

Portland averages 37.50” of rainfall at the airport  55”+ above the elevation of 500’ and higher

Portland averages 4.3” of snow per year in the last 30 years.

In the last 30 years PDX has been as low as 9ºF and as high as 106ºF (twice).

Zoning out in Portland

Seasonal Affect Solution

I don’t know about you but after the first 14 days of December drenched us in more than 10″ of rain and we broke the record for most days in a row with .25″+ of precipitation me and my garden are a sodden mess. Its not only the damned rain, its the darkness and even myself a dyed in the wool Oregonian has had more than enough. Screw the “drought” and to hell with the snowpack. I’ve even taken things by the horn and booked a week in Palm Springs in late February. I have a feeling by then I will have eaten my umbrella and I’ll need many hours perched in blinding vitamin D. Staring at cacti. Cacti that are actually happy to be there in their appropriate climate.

Circumvent the SAD

My friends and co-workers are quite aware of my grumpy disposition by mid-winter and though I have shiny palms and bougainvillea to look forward to I have another plan to circumvent the blues. Its called flowers. A friend and owner of a big nursery once told me that foliage is king. While I agree I have to admit to the curative power of flowers. When I began my current garden four years ago I set aside a portion just to counteract my seasonal asshole disorder. Its my winter garden. And with experience and circumspect planning I can say that it has achieved its purpose.

Do it for yourself, do it for a smile.

Over the years I’ve kept a mental tally of all the winter blooming plants in our climate and when they arrive to shine. Its not so much about an orgasmic show but more about actual movement and growth in the dormant season. Its about freakin’ hope. These plants shirk the cold, shrug off the wet and push right through. I’m not saying that you should have an entire garden of winter interest plants- to ignore the other three seasons would be a travesty. But to let a little smile creep across your face on Martin Luthers birthday or to greet Valentines Day with actual flowers in nature can set you free. Let me describe:

Pick a spot, any spot.

My own winter garden is behind my garage. Unless you know to look it escapes the notice of just about everyone that visits my garden. Tucked away just for me it houses a months long display of plants that quietly rock my world. There is an obvious advantage to cool season bloomers- not only are they brightly conspicuous in the dank of winter they bloom for such a long, long time. Flowers last forever in the natural vegetable crisper that is an Oregon winter. And it doesn’t take a whole lot to make a big impact. In my case I’ve shoved together a trove of plants in a 10′ x 12′ area that reliably perform.

Where to begin?

On my path to plant discovery I’ve amassed quite a collection, I’ve tried literally thousands of plants and killed many hundred. Now I know how to maximize the impact in just a small space. The first and most important thing you need for a winter garden is Hamamelis. (Witchazel) a small tree that will perfectly set the mood. They range from luminous yellow to orange and red- even purple with curly curious flowers. My own is Hamamelis x intermedia ‘Aphrodite’- large, fragrant orange flowers crowd the twigs of this cultivar. In a normal year it begins to shine in late January and persists to early March. Everyone should have one- part shade and moisture retentive soil suit it and not just flowers but the graceful angel shaped crown and fall color endears them as well.  Trust me, you will never regret a witch hazel. And if you can’t wait until January cut stems force easily inside once their flower buds have set. These are easy to spot.

But back to the beginning.

I should start at the beginning of winter. Thats not technically the calendar equivalent but I base the beginning, November 15, on the first week we could have an intrusion of arctic air. And my own end of our short winter is February 15 when its rare to impossible for Jack Frost to piss us off. One of the great glories of gardening is discovery and once I discovered Sasanqua Camellias a whole new world arrived. Typically they flower from October to January and even if you are not a Camellia fan you have to admit there’s a certain amount of cheer in flowers at that time of the year. They come in many colors, take shade or sun and are easy, easy to grow shrubs. They pop off masses of lightly fragrant flowers for months. Just when you think that they have frozen barren of blooms a whole new set erupts. In my own garden I have two that I cherish for their display.

Camellia sasanqua ‘Hugh Evans’

Simplicity to opulent fragrance.

‘Hugh Evans’ is a single bright pink and it pops out vividly colored flowers for months. I adore its small forest green glossy leaves. And now that I see the combination of Sasanqua Camellias with vividly colored fall leaves it opens up a whole new tableau of aesthetic joy.  My second is ‘Yuletide’- true red flowers- no pink, strongly in the orange spectrum with a yellow center. And true to its name it peaks right around Christmas. Other species of winter blooming Camellias offer a huge compilation of choice as well. My favorites- which are hybrids are ‘Tulip Time’- huge, chalice shaped pink flowers and  ‘Minato-No-Akebono’. Both open flowers beginning in mid-January and the latter has single pink flowers intensely fragrant of freesias. These I train to a wall to maximize space. They endure dense shade or a lot of sun and require only a few diligent soaks in summer.

Let the leaves be your canvas.

The heart of my winter garden is a shrub that I dearly love. It is Fatsia japonica ‘Variegata’. Huge 18″ wide leaves are touched on the edges in white. In October to December enormous flower structures emerge from the foliage and like a 60’s light fixture they host cream colored balls that are flowers. It takes me by surprise every year. The bold evergreen foliage is part of a wall of foliage that separates me from my neighbors and their yappy dog Paige and chickens. (Nothing against chickens). A pair of clumping bamboos provide an arching wall of dainty foliage on my favorite species Boorinda angustissima. It loves shade, its incredibly drought tolerant and has risen to 16′ tall arching to 8′ wide. I love everything about it. Its the epitome of grace. On a west facing partially shaded wall I host an espaliered Pyracantha x graberi a hybrid I prize for its true RED not orange berries and glossy foliage. The berries are a vivid decoration and treat for birds. Adjacent to that is a shrub I find indispensable- Grevillea x ‘Neil Bell’. Dapper sage green foliage perfectly combines with spider shaped tomato red flower clusters. This large growing evergreen blooms YEAR ROUND and once the hummers have found it expect a lot of riotous territorial spats. To 8′ x 8′ tall- it gets absolutely no care or water from me. The red flower tones work perfectly with the long lasting fruit of the Pyracantha.


Fatsia japonica ‘Variegata’

The lower layer flows with fun.

On the ground I have arranged what I now regard as the most reliable winter treasures. Behind a deep green dwarf boxwood hedge I’ve placed Hybrid Hellebores- 3 whites, 3 pinks, 3 yellows- in various double to single flower forms. Arranged at their feet is the remarkable winter flowering Cyclamen coum. I pick the varieties with the most dramatic leaf coloration because that in itself is a show before the scads of dainty pink/purple/white flowers amass beginning at the new year.  Its a floral combination you cannot beat rivaling summer opulence. Cyclamen coum is a prodigious seeder so you need only start with a few and in subsequent years the tapestry of leaf coloration and flower color is a delight. Here a single clump of a favored and easy to grow perennial Iris unguicularis (Winter Iris)  alights with violet blue flowers continuously from November to March. It tolerates dry shade as well as full sun and forms grassy clumps that cradle the fragrant flowers.  All of this is at the foot of a winter flowering Mahonia x media ‘Charity’. Its a tiered evergreen of total refinement and the luminous spikes of yellow flowers also beckon to hummingbirds. Its a big plant so give it elbow room and remember that the leaves pack a prickly punch.

Cyclamen coum – selected leaf form

Tommy to the rescue

In January bulbs make their appearance. Massed beneath the Witch Hazel is the fantastic winter blooming Crocus tommasinianus- or Tommy Crocus for short. I’ve chosen the cultivar ‘Ruby Giant’ which is a bit misleading- the flowers are large but vibrant purple. Nothing bothers this bulb. Squirrels seem to shun it, winter slugs avoid it and it cheers me immensely that its grassy foliage has the good manners to disappear into dormancy by mid spring. In time it seeds itself prolifically and shows up wherever it wants- this means you can start with just a handful and before you know it you have colonies. An ideal counterpart is Galanthus nivalis – Snowdrops. I brought them from my old garden and I don’t regret it a bit when their snow white drops of charm emerge. They too disappear cleanly by mid-spring. If you are a fan of blue flowers take a look at the demure Chionodoxa luciliae (Glory of the Snow) with star shaped flowers of ultra marine. It too seeds itself around in rich soil that can even bake in summer.

Garlands of love

Finally, I have two vines that bring immense happiness. I’m a total fool for the genus Jasminum and winter flowering Jasminum nudiflorum is a joy. More of an arching scandent thing its tubular glimmering yellow flowers appear off an on in mild weather. I once saw it trained dutifully on a wooden white painted trellis- it was sunshine itself. Give it room and at least half a day of sun. Another enchanting plant is the vine Clematis cirrhosa ‘Wisley Cream’. I’ve grown other winter flowering C. cirrhosa cultivars and they were NOT that great. Kind of weedy actually- but this is exceptional.  Its finest attribute is 2″ wide luminous yellow bells from October to February. Its a vigorous but not obnoxious vine with fine glossy  evergreen leaves. Shade or sun it prospers. If I had the room I would let it decorate the superb winter blooming shrub Viburnum x ‘Charles Lamont’   with large white/shell pink clusters of fragrant flowers initiating at the beginning of the new year.

The tip of the iceberg.

This is just a sample of all that is possible. Don’t forget Heaths (Erica)- and there are other colors beside Good N Plenty pink and white, Grevilleas have a host of species and cultivars for nearly year round interest and its a genus whose time has come to Oregon. Winter honeysuckle emits its mysterious perfume- Lonicera x standishii- a large shrub tolerant of any condition. A personal favorite at Xera is Arctostaphylos x ‘Austin Griffiths’ a large Manzanita with extravagant mahogany bark and masses of clear pink urn shaped flowers for two months beginning in January. I’ve focused on blooming plants but don’t neglect architecture- bark, the total art of Agaves and Yuccas whose form and sunny origins can send you away from the dismal gray.

El Nino- One wet mother.

We are on track to have the wettest December on record. Thats a tally of more than 13″ of rain. This isn’t surprising for an El Nino. And the projected forecast is showing not much change in the next three weeks. Long range forecasts hint at a southern intensification of the Polar jet possibly merging with the Subtropical jet and dipping southward bringing storms into California. I hope this pans out for their benefit and it may just give us a little respite from the the deluge. Happy Holidays.








Seasonal Affect Solution

Vines: You Spin Me Right Round


Vines add romance and luxuriance to gardens. They allow the gardener to extend vertical space- you can garden up and over your head. They make use of not just the ground but the sky. Many people shy away from vines because they either don’t consider the space or they think that they are a pain in the ass. Its been a personal goal of mine to use vines to their best advantage and to solve any problems that the gardener might incur. There is a spectacular array of vines that are available in our climate and it is a pity to not take advantage of that bounty. I’ll discuss some of my favorite lesser known vines that are as spectacular as they are useful. There are several things you should consider before planting but with a little planning and information you can make an informed choice, achieve what you want, and have a long lasting easy to grow bower.

Wind it up

The most important aspect to vines is to understand how they climb; match the support to that adaptation, and proceed. First: there are twiners. These are vines that grow around supports attaching with firm spiral effect. These vines as all plants grow from the tips and as they grow they literally spin around and adhere to whatever support you offer. Generally the smaller in diameter support you supply the easier it will be to get the vine to soar. For instance, don’t expect a twiner to vine around anything wider than 5” in diameter. The very best way to deal with these is to train them to an appropriate support when young. That means you should start with a support no more than three times the diameter of the vine’s stems that you intend to train. This will allow the vine to twine and purchase with minimum effort and it will adhere more quickly.  In time their trunks will swell prodigiously and hold themselves in a free standing habit.  My favorite way to deal with this is to provide a permanent guy wire for the twining plant to adhere.

Can I have your support?

The very best support is #4 size copper wire. Not only is it the perfect diameter it is easily conformed to whatever shape or size you deem appropriate for your twiner. This means you can effectively wind the wire in a spiral shape up walls or along fences and the vine will follow. I like to attach it to a fair sized eye hook at the top or along as I go. The wire may be threaded through the ‘eyes’ and this will not only guide it but hold it in place. If attached to an eave on the house this means that you can easily unhook the vine and lay it down if you need to wash or paint the house.  Additionally, this keeps the foliage away from the house which encourages air circulation and prevents wear on the house surface. If done gently this means the vine can be carefully lifted and reattached when the chore is done. Number 4 copper wire is incredibly strong, but is readily bent and will hold its shape. Its tough and can support some of the heaviest of vines with no issue. It is easily obtained at home improvement stores in the electrical/wire section. Usually it sells for approximately .90-1.05/per foot and this may sound expensive at first, consider that it lasts for many decades and you can  re-use it indefinitely if the need arises. Just as charming it will take on a natural verdigris finish with time. It is the epitome of versatility. You can string it up and along fences and walls- you can have a vine and train it virtually anywhere. My favorite application is to wind it around stout pillars in a spiral configuration. The vine will then follow the wire and appear effortlessly to float around the pillar.  Evergreen twining vines such as Apricot Star Jasmine (Trachelospermum var. mandianum  Zone 7b) conform to this beautifully and clothe pillars from the base to the top with a garland of dapper evergreen foliage and spangles of fragrant citrus scented pale yellow/apricot flowers.  Copper wire can be used to train vines to the top of pergolas or arches- it will get you there and up and over the top.  Its only limit is your imagination.

I can have it all

If you have ever lost a Jasmine to a freeze you may be wary to try any other. Well, it turns out  you were growing the wrong Jasmine. Florist’s Jasmine (Jasminum polyanthum Zone 9a) is frequently sold- especially at late winter and early spring garden shows as hardy. Well it isn’t- and though it will often reemerge after freezing to the ground in winter it blooms on wood from the previous year so that it will never bloom again. A huge downer.  Enter Poet’s Jasmine (Jasminum officinale Zone 7b) which is the Jasmine we should be growing. There are several extraordinary selections of this anciently cultivated cold hardy vine. My favorite is the cultivar Jasminum officinale ‘Affine’.   Vigorous new growth is tinted maroon and in June to September a phenomenal display  of individually 1” wide pink budded powerfully fragrant flowers in clusters that open to sugar white. Its sweet perfume wafts far on warm summer nights and for months the starry flowers are shed in a fragrant cascade. In autumn the deciduous foliage takes on apricot and yellow tints before shedding. It is incredibly drought tolerant- and its shunned by deer.  I could never be without this lovely vine.  And it will NEVER freeze away. Its a large, vigorous twiner to 20’ tall and 10’ wide in 8 years. Consider it for a pergola or long fence.

Jasminum officinale ‘Affine’

Xera’s Top 5 Most Fragrant Vines:

  1. Trachelospermum j.var. mandianum (Zn7b) Citrus scented. Apricot Star Jasmine
  2. Lonicera x americana (Zn5b) POWERFUL fragrance carries 30′. Pink Honeysuckle
  3. Jasminum officinale ‘Affine’ (Zn7b) The sweetest perfume. ‘Affine’ Poet’s Jasmine
  4. Trachelospermum jasminoides (Zn7b) A classic summer fragrance. Star Jasmine
  5. Mandevilla laxa (suaveolens) (Zn8a) Sweet, subtle cologne. Chilean Jasmine

Regal pedigree for shade

Gardeners tend to go to pieces for certain types of variegation. Not all variegated plants can pull off what can be gaudy, busy, mismatched. This vine skips gaudy and goes right for beautiful. Kadsura japonica ‘Fukurin’ (Zone 7b) is a regal evergreen vine with a fine pedigree. This member of the Magnolia family has glossy leaves that are large and tapered with the edges picoteed in  bold cream and a center of sage green. New growth is liberally flushed with pink on its way to maturity. This vigorous twiner prefers a fair amount of shade- ideal in a woodland. Its small double petalled white flowers transform into strings of bold red berries by fall. It is fairly quick in its ascent and can easily cover a pergola or arch. 15’ tall and 10’ wide in time. It appreciates rich, well drained soil and regular summer water for maximum growth and impact. As far as I can tell it is perfectly hardy and evergreen to zone 7b (5ºF).  I suspect it could endure colder by simply becoming deciduous. Its my number one choice for a vine in shade.

The queen of vines and a prince for winter

Clematis which adhere to supports by modifying their leaf stems and using these to hoist their way along can also be made to climb copper wire. Perhaps gridded trellis (again with small diameter wires to surround) is the best way to display these prodigious bloomers. They, as many vines, are famous for becoming bare at the knees. Plant a shrub in front of the base of the vine and all is well.  The large flowered varieties are so well known that I will forego any more mention in favor of a species/cultivar that I find has great charm at a wonderful time of year. More gardeners should know and grow Clematis cirrhosa ‘Wisley Cream’.(Zone 6b) From October to February it is clad in luminous light yellow/cream pendulous bells. It wears small, evergreen glossy leaves and is vigorous but not rambunctious.  In fact, this and many Clematis are seen to their best advantage, I think, not on artificial supports but trained wildly into shrubs or trees. In my own garden  ‘Wisley Cream’ displays its bell shaped flowers as a garland ascending  a 20’ tall Italian Cypress.  The cream colored bells are brightly conspicuous against the deep green foliage of the cypress. This mediterranean native is tough, despite its diminutive scale of leaf and flower and cold hardy as well as drought adapted when established. It tolerates a fair amount of shade surprisingly. Blooms appear for an extended period and are welcome and cheery in the dullness of winter. It is also a prized food source for overwintering Anna’s Hummingbirds. To 15’ tall or taller and 6’ wide. Prune after blooming if needed.

Clematis cirrhosa ‘Wisely Cream’

Self determination

Vines that attach by rootlets that emerge from the stems must be treated in a whole different way. Self clinging is an an apt description. They should never be allowed to climb the walls of a house or structure where you do not want potential damaging long lasting effects. A fence, a pole, a barren ugly wall is the appropriate home for this group of self determined plants. A perennial favorite in this group is the hybrid trumpet vine Campsis x ‘Madame Galen’ (Zone 6a) Enormous fluted tubular flowers are saturated on the inside and out with bold apricot orange. The huge flowers virtually obscure tiny visiting Hummingbirds that pursue it voraciously.  This vine is a tropical appearing floral crescendo for summer into autumn. Not small it requires ample space, 10’ x 20’ to really show its potential. Once established it is tolerant of every condition save for dense shade which deters bloom. Its completely deciduous dropping its compound pretty leaves after they switch to yellow in fall.

Sometimes clingy is a good thing

If sunshine is at a premium there is a duo of self clinging vines that are poised to explode in popularity  These seldom seen species of climbing Hydrangeas have everything required for greatness. They are evergreen with incredibly glossy handsome leaves a trait that leaves them perfect for clothing nearly any surface in part shade to shade. (I have experimented with these in full sun and have had great success as well.) Hydrangea seemannii (Zone7a) is the first to gain notoriety and among those who have grown it has a legendary reputation. The 3” long by 2” wide shiny leaves appear densely and form a curtain of layered foliage. In summer and on wood from the previous year huge 2” wide round white buds erupt to reveal a circular configuration of white  fuzzy true flowers surrounded by large creamy sterile bracts. I have grown it in very dense shade as well  and had excellent results. Most spectacular is its display in the Heronswood Garden. There it was sent soaring up the trunk of a 75’ tall highly limbed Douglas Fir. My first encounter with this vine and it was in spectacular early summer bloom. Very similar and just as adaptable is the species Hydrangea integrifolia (Zone 7b) which adheres itself to any surface by strong rootlets and it has juvenile leaves which display deeper serration before maturing to entire and glossy. On mature vines they are host to a massive display of white flowers in late spring to early summer. As with Hydrangea seemanii these can be slow in their youth but as they establish growth increases at an exponential rate. Not only are they tolerant of shade, they also shirk drought- ideal for life among the greedy tree roots of the Pacific Northwest forest floor. Each achieves 35’ ultimately- give them as much time and space as they require.

I wanna reach out and grab ya!

Vines that attach by tendrils are another ingenious adaptation to achieve altitude. The modified curly stems that emanate from the canes attach to any support that is not too huge. Passion vines  (Passiflora species), and Grape (Vitis species) are examples of vines that attach by this method.  This adaptation demands that a trellis or wire should be sturdy. (Here, again, #4 copper wire works beautifully). Their best display, however, is along wire fences and fine wooden lattice.  Nearly all tendril climbers represent vigorous species so give them ample room. Blue Crown Passion Vine (Passiflora caerulea Zone 7a) is a perfect example and a very, very easy to grow vine tolerating the poorest soil- which actually improves the amount of blooms and thrives on the barest minimum of summer irrigation.  The first nursery in which I worked had a 6” wide patch of gravel between a wire fence and a paved alley on a hot southern aspect adjacent to the nursery.  I literally carved a hole in the gravel and plopped in a Blue Crown Passion Vine and I never expected it to survive. It did spectacularly and with nearly continuous runoff from the nursery irrigation it exploded and eventually spread nearly 25’ in either direction on a wire fence and shading the whole nursery in verdant foliage and fascinating flowers. This spring we are offering a trio of new hybrids of Passiflora caerulea.  These are  free flowering and permanently compact Passion Vines brand new to the market.  Slightly less hardy than the standard species  these (Zone7b/8a) will be much, much easier to accommodate in small gardens maturing at just 8’ to 12’ tall.  They are: ‘Silly Cow’  with round, vivid, blue and purple flowers, ‘Star of Sorbitron’ with purple filaments transposed on creamy white sepals, and ‘Betty Miles Young’ with lavender sepals and deep- nearly black filaments in the center. Not only improved in hue, they incorporate the variety of flower form from semi-tropical species in this enormous North and South American genus.

Garden in the sky

This is just a hint of what is possible with vines. We continue to search out new species and varieties that are adapted to shade, drought, deer, that support spectacular flowers and fragrance. Literally, the sky is the limit. Take note of #4 copper wire and let it guide your imagination. Remember that vines make use of unused space in a garden. In your search find out how a vine climbs as well as its ultimate size. Does it require pruning? Does it bloom on new or old growth? Evergreen? Fragrant? Arm yourself with the facts and you will become addicted to vertical gardening.


Vines: You Spin Me Right Round

Cold snap and saggy Bananas.

A brief weather update and review of the surprisingly sharp freeze in late November. This freeze was memorable for several reasons. It didn’t break any records by a long shot but it was prolonged and in the realm of global warming sufficient to be of note.  Portland recorded 6 and as of this writing 6 days below freezing in a row. After the warmest October on record this is a departure. Portland dropped to 24º on two non-consecutive nights but the real story was in the outlying areas. The NOAA hinted ONCE that temperatures in the most wind sheltered areas MIGHT see upper teens. That was more than true in several locations. Highlighting this period of weather was a rex block and N. N-easterly flow. The offshore flow that dominated out of the Gorge was not especially strong but it did have an effect on the ultimate lows. When the wind stopped the temperatures dropped.

Those chilly hinterlands

Remember that cold air sinks. That is counter intuitive to what you hear about elevation. But in a stable, cold, dry regime the lower you are the lower you go. So the wind sheltered valley areas with the least wind had the lowest temperatures. Eugene was the clear winner with four days in a row with minimums in the upper teens. (19º, 18º, 17º, 18ºF). Thats impressive even for the coldest time of the year. What was striking was that on all but the final day of the cold snap the daytime temperatures recovered to the low 40’s. This is unusual for an inversion. Portland recovered to 50º+ on two days- unusual.  Other calm low elevation lows were 19ºF at Hillsboro, Corvallis,  and Vancouver (which often records exaggerated lows so that recording station is suspect), and 20º on two nights in Aurora and Salem. Those are all official reporting stations. You might have noticed much different values in your own back yard. I’ll get to that.

Wind is a mixer

Portland was especially prone to mixing from east winds. These winds when they surfaced kept the ultimate lows from plunging. Many neighborhoods where the east wind prevailed failed to record a hard freeze while others dropped precipitously. Location, location, location. Troutdale where the wind was steady 20-30mph gusting to 35-40mph for 5 days straight had only two nights below freezing. Match that to PDX just 8 miles to the west with 6 nights. Wind mixes things up. Also in this episode the calm conditions really allowed cold air to settle thats why reporting stations in the bottom of the valley recorded such cold temperatures. In the end a weak low  from the SW intruded with a dying front on the final day and gave weak spats of sleet and freezing rain in spots.

Compare this to the past- No comparison

The last great November freeze was unarguably 1985. For nearly two weeks arctic air held sway with lows ultimately dipping to 13ºF at PDX and throughout the Willamette Valley. High temperatures were below freezing for 9 days and snow fall occurred early and then spectacularly late in the freeze. This freeze was more representative of what you would find in December-February. And it wasn’t unprecedented. It happened in 1952 and 1955, 1978. But there has been nothing approaching it since. (Global warming?).  All four of these freezes were of note not just for their record breaking early occurrence but were ruinous to agriculture (and gardens).  Even more surprising was that arctic air never really re-0ccurred in two of these winters. 1978 was an outlier- arctic air came back later in the year and 1985 was a cold year but after November nothing of arctic note really impinged. And its worth noting that in many years when the lowest temperature happens in November it isn’t exceeded later in the year. Thats it. Thats winter. Will it be this way this El Nino winter? Time will tell.

The next several weeks show a zonal flow with an active jet stream and mild and wet conditions. Not necessarily a classic El Nino pattern but we haven’t even reached winter yet so we have to wait and see. I’ll  update this blog as weather and my ideas for blogs hit me. Until then, clean up the weeping snot of your bananas and kiss those annuals good bye. heh.


Have a great Holiday season.






Cold snap and saggy Bananas.