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Gardening Answers Knowledgebase

Plant Answer Line Question

Keywords: Pruning shrubs, Effect of storms, Arbutus unedo, Frost

I live in Monroe (Zone 7). Two years ago I planted 3 Arbutus 'Compacta'. I have never pruned them. This year they took the cold winter pretty hard: over half of the leaves are golden/brown/black, with some already falling off. Will the leaves be replaced or do I need to cut the branches and stems to those leaves and hope for the best? The tree/shrubs are in well-drained soil, mulched, facing south/southwest. The leaves hurt the worst were on the upper and north facing side.


It sounds like you are seeing winter damage on your plant. You should probably wait and see if the plant returns to more robust health, and to see if new growth develops where those leaves have dropped before deciding whether to prune it at all. The local web site Great Plant Picks indicates that Arbutus unedo 'Compacta' can be cold-sensitive. Arbutus unedo 'Compacta' tolerates a wide variety of soil conditions. It grows best in part or full sun and is drought tolerant once established. There are few insect and disease problems, though it can occasionally get aphids and there may be fungal spotting on older leaves if grown in very poor soil. Foliage and flowers may be damaged in extremely cold winters. If you think that there is something else going on besides winter injury, I would recommend taking a sample to a Master Gardener Clinic for diagnosis.

Below is information on winter injury from Washington State Extension and the Pacific Northwest Plant Disease Management Handbook.

Date 2017-05-11
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Plant Answer Line Question

Keywords: Arbutus unedo, Pruning shrubs, Osmanthus, Quercus, Viburnum, Pruning trees

When is the proper time to prune Arbutus unedo? How much can be pruned at a given time? Same question for Osmanthus decorus, Viburnum odoratissimum, and Quercus reticulata.


According to The American Horticultural Society's Pruning & Training edited by Christopher Brickell (DK Publishing, 1996), you can prune Arbutus unedo in spring, as soon as danger of frost is past (that would be early April in Seattle), but keep pruning to a minimum. Some people choose to remove lower branches to create a taller trunk on younger trees.

The book Pruning: A Practical Guide by Peter McHoy (Abbeville Press, 1993) says that Osmanthus decorus can be clipped in late summer. If you want to limit its size without clipping, prune back long shoots to points far inside the shrub in late spring or early summer, after flowering. If the plant is overgrown, you can spread this type of pruning over two or three years, but do not do it annually. I am not familiar with this species of Osmanthus, but I do know Osmanthus delavayi, and grow it as a hedge. It is sheared after it flowers, and then probably two more times before winter. I did have to prune the top back quite hard last year, and this did not seem to cause any problems, but O. decorus may have different needs.

I could not find information about Viburnum odoratissimum specifically, but most pruning books have general guidelines for Viburnum species. Unless you do not mind losing the flowers, it is best to prune when flowering is done. If you are growing V. odoratissimum as a tree, then special pruning may be needed. George E. Brown's The Pruning of Trees, Shrubs and Conifers (Timber Press, 2004) says V. odoratissimum is somewhat tender, and may grow best as a standing bush with the protection of a wall, using ties in places to keep it close to the wall. The only pruning he mentions is cutting out older wood after flowering, and tying new growth back to the wall (if you are growing your plant in a site where you can do this).

According to the Peter McHoy book, oaks do not require routine pruning. Brown's book says not to prune oaks between mid-spring and mid-summer, as a means of protecting against oak wilt and beetle infestation. If you must prune, do it in winter.

Quercus reticulata is not a common tree, nor are the species of Viburnum and Osmanthus you are growing. Unless there are compelling reasons to prune harder, I would suggest sticking to the 3 D's of pruning: take out only dead, diseased, and disordered branches. Another general rule of thumb is never to remove more than 1/3 of the plant at one time. You might want to consult a certified arborist as well. You can find arborists through Plant Amnesty's referral service or the Pacific Northwest Chapter of the International Society of Arboriculture.

Date 2017-05-26
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Plant Answer Line Question

Keywords: Morella californica, Arbutus unedo, Trachelospermum, Osmanthus, Native plants--Washington, Screens, Wisteria, Viburnum

A friend asked me about screening two large propane tanks that, unfortunately, have had to be placed in front of their home on Camano Island. She mentioned wisteria to me and I shuddered. I've seen this plant do a lot of damage to trellis and home alike. Can you recommend, instead, an evergreen solution to this problem?


I am not familiar with the size and shape of propane tanks, but perhaps evergreen shrubs might work to screen them. A concern would be the proximity to the house, and any needed clearance for paths, doorways, and windows. I think you are right to avoid Wisteria. Does your friend prefer the idea of planting vines, or would shrubs be acceptable?

Here are a few suggestions for evergreen shrubs, with links from the local web site, Great Plant Picks:

Some good information is also available about plants for screening (from Virginia Cooperative Extension) and vines, especially evergreen vines such as Trachelospermum jasminoides, which might be a good solution. Local garden writer Valerie Easton on has written helpfully about hedges, as well.

Date 2017-05-26
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Plant Answer Line Question

Keywords: Pittosporum, Wind-tolerant plants, Morella californica, Arbutus unedo, Osmanthus, Pyracantha, Chamaecyparis, Arctostaphylos, Pinus, Cotoneaster, Ceanothus

I am looking for evergreen hedges that will tolerate a windy site. Do you have any suggestions?


Sunset Western Garden Book (2007 edition) has a list of wind-resistant plants. From that list, there were a few plants which meet some of your site's needs (evergreen, fast-growing, about 7-10 feet tall). They are:

  • Arbutus unedo (Strawberry tree)
  • Arctostaphylos (Manzanita)
  • Ceanothus
  • Chamaecyparis
  • Cotoneaster
  • Escallonia
  • Morella californica
  • Pinus species (you would need a dwarf pine for your size limits)
  • Pittosporum (many of these grow taller than 10 feet over time, but P. tobira might work)
  • Pyracantha

I don't know if it is tolerant of winter winds, but Osmanthus delavayi makes a nice, dense evergreen hedge with flowers, and reaches about 8 feet. It grows fairly quickly also.

Two good resources for finding more information on the plants above are Oregon State University's Landscape Plants and Great Plant Picks.

Also, I found an article (no longer available) on wind tolerance from Colorado State University Extension which may be of interest. Here is an excerpt about the physical characteristics of wind tolerant plants:

"When considering which trees and shrubs do well in windy conditions, examine the shape and thickness of the leaves, stems and branches. Wind-resistant trees usually have flexible, wide spreading, strong branches and low centers of gravity. Wind tolerant shrubs often have small, thick or waxy leaves or very narrow leaves (or needles), to help control moisture loss. Plant species that have large, flat leaves "catch" wind. These plants have a tendency for branch breakage when strong gusts blow, or if laden with heavy, wet snow. Evergreen (conifer) trees are an excellent choice, having needles and being flexible in high winds."

Date 2017-04-22
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Plant Answer Line Question

Keywords: Arbutus unedo, Pruning

I have an Arbutus unedo 'Compacta' planted in my garden, close to the property line. My neighbors want me to shear the top and sides so that they can see the view beyond it while seated on their sofa. I really don't want to do this, but I need to provide a convincing argument that shearing is not the best way to prune my Arbutus.


It's difficult to imagine topping and shearing the compact form of Arbutus unedo which is unlikely to exceed 10 feet. Ideally, it would need no pruning whatsoever. Local pruning expert Cass Turnbull of Plant Amnesty classes Arbutus unedo with other "tree-likes," shrubs or small trees which should be maintained with a tree-like shape. Below are excerpts from her recommendations on pruning (and there is a brief guide on Five Reasons to Stop Topping as well):
"DON'T: Ornamental trees should never, ever be topped. And shrubs should rarely be sheared (except real topiary and formal hedges). Stripping all of the side branches off of a mature pine or any other tree or shrub, is also a no-no. Stripping is not to be confused with selective thinning, which can also make shrubs and trees look open and Oriental.
Best let to get big. Not to be pruned heavy-handedly. Good selective pruning can open them up and make them look less oppressive, can train branches around gutters and off of houses, and can bring more beauty out of your plant. These shrubs are the hardest to do. Never remove more than 1/8 total leaf surface in one year. It stresses them or it can cause a watersprout-rebound effect --- ick! Tree-likes have stiffish branches, generally. Examples of tree-likes include rhododendrons, andromeda (pieris), magnolias, deciduous Viburnums, camellias and witch hazel.
Most tree-likes just need to have all of the dead wood taken out.
If you still want to do more:
Take out suckers (straight-up, skinny branches from the base and trunk of the shrub or tree.
Take out any big crossing, rubbing branches and double leaders (two main top branches with a narrow branch-crotch angle) on trees.
Take back or remove any branches hanging on the ground, if only up 1/2".
Take out the worst of the smaller crossing, rubbing branches --- choosing the healthiest and best placed branch to remain.
Prune to shorten or completely remove the worst wrong-way branches that start from the outside of the shrub, and go the wrong way back into the center and out the other side. Sometimes a side branch has a smaller branch that heads too far up into the next "layer", or goes too far down. You can cut some of these off to add more definition to your shrub's branches.
If you have two parallel branches rather close together, it may look better to remove one. If you, have three parallel branches you may want to remove the center one. This will make things look nicer.
Before you finish, stand back and observe. If necssary, you may sparingly shorten some branches on tree like shrubs (not trees). Cut back to a side branch."

Another resource, Peter McHoy's A Practical Guide to Pruning (Abbeville Press, 1993), says that Arbutus unedo "can be trained with a single trunk, as a multi-stemmed tree, or left unpruned to form a dense shrub." He does not mention shearing it like a hedge. According to The American Horticultural Society's Pruning & Training edited by Christopher Brickell (DK Publishing, 1996), you can prune Arbutus unedo in spring, as soon as danger of frost is past (that would be early April in Seattle), but keep pruning to a minimum. Some people choose to remove lower branches to create a taller trunk on younger trees.

Your neighbors may be under the misapprehension that shearing will control the size of the plant. In Cass Turnbull's Guide to Pruning (Sasquatch Books, 2006), the author says, "Because shearing is nonselective heading, it will stimulate bushy regrowth, creating a twiggy outer shell on sheared plants. This layer of twigs shades out the interior which then becomes leafless and full of dead leaves and deadwood. Meanwhile the outher shell becomes thicker and larger every year because, as it is sheared repeatedly, it must be cut a little farther out to retain its greenery. This dense, twiggy outer shell makes size reduction difficult because cutting back too far exposes that ugly dead zone inside the shrub. [...] Therefore, shearing is not a good way to control the size of a shrub. [...] Shearing is also a drain on the health of plants.[...] Shearing plants creates the antithesis of a healthy environment, making shrubs more prone to insect attack, deadwood and dieback. It adds a general stress on plants because the rapid, profuse regrowth promoted by repeated heading depletes their energy, and their resulting weakness and tender growth makes them more susceptible to injury from freeze or drought. [...] shearing often defeats the purpose of shrubbery, usually by cutting off the flowers, but other characteristics get subverted as well." If these are not reasons enough, it is not cost-effective to shear, as it must be done repeatedly."

You may wish to contact Plant Amnesty to obtain a referral for a consulting arborist who will speak on your behalf.

Date 2017-07-18
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May 31 2018 13:14:08