Pruning guide- Shrubs, Manzanitas

Shrubs and pruning

Working in both wholesale and retail and selling a LOT of unusual shrubs I can tell you that one of the most perplexing issues facing a new gardener is pruning. People are deathly afraid of doing it wrong and as we’ve seen more than our share of butchering by landscrapers in this climate there should be some healthy fear. The problem is there are literally thousands of shrubs that thrive in our climate. And I’ll try to impart my best advice on how to approach this. This blog post is about pruning shrubs, I’m not going to go into trees and vines but some of the advice may be applicable.

Do you need to prune at all?

That is a great question. Most pruning is done to restrict the size of a shrub that is too big for its allotted space anyway. The first and most important thing you should do before planting is get a realistic size for your prospective beauty. When I write our tags I try to give the best estimate of what that ultimate size may be. To be honest very few shrubs stop growing- they may just grow slower and so that adds to my dilemma. In some cases I give the size in 5-7-10 year increments. A garden changes an awful lot in that time frame but at least it gives the gardener perspective. Some of the most important ideas to consider are the location, water availability, and soil conditions.

Too Fat and Happy

For instance, many cultivars of Ceanothus that we grow are California derivatives. They were selected in a climate with MUCH less spring rainfall and soils that are less than perfect. I learned early on to factor in the PNW conditions and basically double the size of these shrubs on our tags. Remember, rich soil (ideal conditions) and availability of water can send a shrub from a less fat and happy climate soaring. That little Ceanothus ‘Concha’ that you plant here can reach tree-like status very quickly. Its funny to see it growing in California where it is a nice restrained plant. Thats why we don’t advise improving the soil with many west coast, mediterranean, Australian, Chilean shrubs. Not only is there no reason to do this you may actually shorten the plants lifespan or leave it open to fungal root pathogens, it can also nudge slightly tender plants into perpetual growth- they never shut down for the approaching winter. That means that they are MUCH less hardy to cold in winter. Summer drought adapted shrubs (West Coast, etc) are used to growing in spring and then going into a second dormancy related to summer drought- they require this to meet their ultimate cold hardiness. Some shrubs that fit into this category are the aforementioned Ceanothus- Cistus, Arctostaphylos, Rosemary, Myrtus, Grevillea- and many other broadleaved evergreens can be nipped or killed, especially by a November or early December Arctic event. The moral is to trust the plants and give them what they are adapted to do. Organize them in your garden by water need or neglect- think of your garden in terms of biomes that you create.  What does this have to do with pruning?

You made me do it.

Pruning can do quite a few things to a shrub. It can restrict the size, it can make a lanky plant fuller, and it can spur many plants into boisterous growth. The first thing you need to know about pruning is how it will affect the plant. Imagine when a plant is pruned in its native habitat. Deer, as an example, can browse many shrubs and the shrubs best defense is to sprout like crazy and replace the lost photosynthetic material with much more. The plant grows into a dense ball of foliage. It may also be said that more light and wind makes a more compact plant and even small compact shrubs can grow openly (lanky) in less sunlight. But if you are unsure how a shrub is going to react- and no tag is big enough to address that and books almost NEVER mention it. Then you need to rely on that most important of all gardening skills OBSERVATION. Make a little test cut on the shrub and see how it responds. Stay tuned and I’ll give you an example of when to do this. But Its important to note that where on the shrub you prune, how you prune it, and most importantly where the shrub is adapted to grow dictates your results.

Some important terms to guide your results

One of the most disastrous outcomes of improper pruning is to eliminate the flowers and thus render a flowering shrub a foliage only plant. Many people who go whole hog pruning on the first warm day in March probably can’t understand why their Rhododendron, Camellia, Lilac, and many other shrubs then don’t bloom- they’ve eliminated that years flower buds. So, I like to refer to OLD wood- shrubs that bloom on one to two year old wood and NEW wood- flowers born on current season growth. This is where observation is your guide. If you HAVE to prune make sure that your first test prune is right AFTER a plant has bloomed. This will almost always put you in safe territory. Shrubs that bloom on old wood grow  after flowering and then set their buds in the summer to fall for the following season. If you then prune when the shrub is in its current season of growth you can still allow the shrub time to grow and set buds in the ensuing summer. Some shrubs besides those already mentioned that bloom on old wood are Viburnum, Berberis, Leptospermum, Osmanthus, Pittosporum, Pieris. If you do measured and careful pruning right after bloom and before flower bud set you won’t wreck next years show.

Lagerstroemia x fauriei ‘Wichita’- Over pruning Crape Myrtles is not necessary and is called ‘Crape Murder’. Little or Light pruning is sufficient. An example of pruning on New wood.

Why would I prune on new wood? 

The most immediate reaction of a shrub to pruning is to branch. On most when you take out the terminal branch bud then that causes the plant to double its growth output. Like a deer browsing the effect is to cause the plant to increase the amount of wood and foliage. Its what nature tells them to do. So, on shrubs that bloom on NEW wood- the current seasons growth pruning can increase the amount of flowers that you achieve in the season. The most applicable example of this is Hybrid Tea Roses. By pruning them back you increase the amount of blooming wood. (Remember that ALL roses do not bloom on new wood- so you should, YES, OBSERVE for a season and do a few test cuts-most roses that bloom on old wood are once blooming.) Pruning of these plants should be done in our climate on or AFTER Presidents Day, Valentine’s Day- mid February. Then we are safe from arctic cold and the growing season has not yet started. Some shrubs that benefit from this are Vitex (Chaste Tree), Shrubby Crape Myrtles (prune lightly), Buplerum fruticosum,  Deciduous Ceanothus (‘Topaz’, ‘Henri de Fosse’, ‘Glory of Versaille),  Indigofera, Oleanders, Jasmine.

Radical Pruning- if you really have to do it.

Sometimes a tired old plant or enormous thing you’ve been gifted by a previous gardener can benefit from some hard core intense pruning. You may be able to resize the plant, reshape it, and reinvigorate it with hard pruning. I’ve seen this accomplished on arboreal Camellias, Rhododendrons, many things. First the plant has to have what are referred to as dormant buds. That is leafless wood on the large branches or trunk that has dormant buds that you can’t see but will be activated in the case of a radical pruning. The best way to achieve the results of a radical pruning is not to just chop the whole thing down all at once. This shocks the plant and though it will respond with the resources of a large root system it can be too much. Rather do measured removal in a few seasons of  no more than 1/3rd of the plant at a time. Though its not pretty and it undoubtedly sacrifices a year or more of bloom it can work. I suggest that you keep the plant well watered during the dry summer to decrease stress.  Some plants that benefit from radical regenerative pruning are: Yews (Taxus), Osmanthus, Lilacs, Hibiscus, Arbutus unedo, Pyracantha. Plants that definitely don’t are Cupressus, Cistus, Ceanothus (evergreen kinds).

Pruning Manzanitas follows slightly different rules.

Manzanita- a pruning primer

One shrub that we LOVE and sell a lot of is Arctostaphylos (Manzanita). I’m going to go into a more specific example of how to prune them because its a little different. Arctostaphylos are grown for their foliage, flowers, AND dramatic bark. Here are a few pointers to get the most out of them. They bloom on OLD wood. That is they grow after winter and spring blooming then set the flower buds for the following season. Tip pruning- is a term that you hear and this is what it is: twigs of the most recent years growth will be clothed in leaves. Tip pruning is just that, after blooming you tip out the bud on the new growth. Thats between any leaves on the stem. On Arctostaphylos the wood grows distinctly. What we call green wood may be pruned and dead wood or leafless wood which will not re-sprout if hard pruned- think of the bare trunks of the Manzanita- there are NO dormant buds.  Tip pruning can apply to any shrub and it does a few different things. If forces the green wood to branch and can lead to an over all denser habit. It will then lead to more tips to produce flowers. This should be done directly AFTER blooming has finished. In the case of many evergreen shrubs the canopy of leaf cover will shade out the lower leaves and they will drop leaving bare legs. If you want to expose the dramatic trunks simply prune off any dead stems cleanly at the surface of the trunk. This increases not only your view but enhances air circulation which Manzanitas dearly love. To complicate it a bit more certain Manzanitas will create what is called a burl at the soil base. This swollen rounded dome of wood contains  dormant buds. It is an adaptation of fire in its native environs. If a burl is present the whole shrub can be cut back to that and regeneration will occur. So, leafless wood on a Manzanita will NOT sprout if cut, green wood with leaves will sprout and if a burl is present regenerative radical pruning can be done.

Slicing and dicing

Remember that when you prune that hygiene is of utmost importance. Keep a clean, sharp secatur and make your cuts thoughtfully. Make cuts on a slight diagonal plane and make them firm and hard. No wimpy cuts that tear or mangle. If you are pruning for shape and results don’t just get in there and start hacking. Make a cut. Step back, look at it and then make the next cut. To be honest most shrubs are fairly forgiving. Be thoughtful and you will achieve your desired results.

Xera Plants will be closing on November 6th for our winter hiatus. We’ll be back open in February barring any arctic events. I’ll still be blogging and posting them on our Facebook page and website. Look for a new website in January 2017. Happy Thanks Giving.


Pruning guide- Shrubs, Manzanitas

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