proper time to prune Arbutus unedo and other plants

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.

pruning Ceanothus

How do I go about pruning Ceanothus?

My impression is that in general, Ceanothus should be pruned with a light touch. Portland gardening expert Ketzel Levine has some opinions on this topic:

“You can certainly prune Ceanothus but there is a bit of a trick. First of all never prune any stems that are larger than 1/4″ wide. Instead prune the very tips of each branch back to where you want it to be. And, since ceanothus bloom on ‘new’ wood, this should provide you with an even more spectacular show next year. Prune after the plants are through flowering; at that time you can also remove the spent flower spikes which will also help it look less wild.”

Ceanothus by David Fross and Dieter Wilken (Timber Press, 2006) says that “an annual trimming of the new growth will maintain a more compact form and improve the appearance of most species. The removal of spent flowers and fruit improves the vigor of many cultivars and will produce a tidier form. Taller species can be trained into small trees with early pruning, and the removal of interior dead wood as plants age produces a cleaner appearance. Once the arborescent character is achieved it is easily maintained and requires minimal effort. Shearing for hedges and formal effect is tolerated by most species if cutting into woody tissue is avoided. Prune immediately after flowering, and only back to the new year’s flush of growth.” The authors mention that although it requires a lot of work, there are some species which can also be trained as small hedges or as trellis plants.

Here is the Royal Horticultural Society’s guidance on pruning evergreen Ceanothus species: “Routine pruning is not essential and in fact are best not pruned. If grown as a bush, promote branching by pinch-pruning the soft tips on young plants in spring. Use secateurs to shorten over-long branches by up to a half in midsummer after flowering. Do not cut into older wood as the stumps may not regrow.”

on pruning heaths and heathers

How do I care now, in the fall, for very well established, huge (in some cases) Callunas? Do they get sheared? If so, how many times a year, and how far back? Also, how do I prune my heaths?

The American Horticultural Society Pruning and Training Manual, ed. by C. Brickell, 1996, p. 183, 193 recommends pruning Calluna (heather) in the same way as Erica cinerea. Prune or trim lightly in early spring, cutting stems back where possible to strong shoots below the spent flower cluster.

Local pruning expert Cass Turnbull of Plant Amnesty says the following about heaths and heathers (Erica and Calluna) in her Guide to Pruning (Sasquatch Books, 2006):
“Spring bloomers are sheared shortly after blooming (in the spring). Summer/fall bloomers are also sheared in the early spring (just as new growth starts), so that the attractive seed heads are left in view all winter. An annual light shearing is all that is needed. Don’t wait. Do it now before the plants get too old and woody. When cut too far into old brown, barren branches, a plant may not break bud and green back up. If you have inherited a mature yard, it may be necessary to severely prune an old neglected heather. It will either regenerate or die. Probably the latter. An exception is the tree heath, Erica arborea, which (…) responds well to radical renovation.”

For further information, consult the following websites of nurseries specializing in these plants:
Heaths and Heathers Nursery

Dayton Nursery

Arbutus winter damage and pruning

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.

on hard-pruning English laurel hedges

We have inherited a 25-foot tall English laurel hedge. The former owner never took care of of so most of the ‘inside’ is just dead branches, but the rest is VERY healthy. Our neighbors would like us to prune it so it’s not obstructing their view, and I’d like to reduce its size so I don’t need to climb a ladder to prune it in the future. Can I cut it back severely, and regrow it into a more manageable hedge? I don’t have the energy to remove it entirely.

I doubt that anyone would ever consider English laurel (Prunus laurocerasus) a manageable hedge plant since what it really wants is to be a tree, but since you want to keep it as a screen, you should be able to cut it back quite hard. It will most likely put on new growth. However, it will look fairly awful while you are waiting for this to happen. According to local Plant Amnesty pruning expert Cass Turnbull (in her Guide to Pruning, Sasquatch Books, 2006), “radical renovations of laurel hedges are common. In the spring, saw the overgrown hedge into the desired shape, except perhaps a foot or two smaller than the final desired size. That’s because it will need that room to resprout and be sheared into a thick green coat again. Be sure to cut your hedge narrow as well as short. It should be narrow enough for one gardener to reach across with a hedge shear. I have only seen one laurel hedge that didn’t recover from this radical treatment. (…) Please avoid heavy pruning on a hot July or August day, as you might burn up some internal leaves or scald the bark.”

pruning and transplanting Ceanothus

I have a mature Ceanothus ‘Victoria’ that I’d like to prune and transplant. When is a good time to do this? It seems as if it has a deep root system.

Ceanothus ‘Victoria’ can be a bit difficult to transplant because the root systems are extensive, as you noted, but it is worth a try. I have transplanted this cultivar both successfully and unsuccessfully.

I would recommend either that you do not prune them or that you wait until August. You do not want them to grow much before you transplant them, and pruning during the growing season will encourage growth. If you prune them in August, they will grow very little.

Extensive pruning before transplanting sets up competition between the root system and the upper plant (responding to the pruning), as far as the plant’s resources are concerned. After transplanting, you want energy directed toward the roots so that they might take hold and also so that growth above ground slows. If you choose to prune the shrubs, I recommend that you prune as little as possible. Prune from the inside, thinning and taking out dead branches, and removing a few lower limbs. You can also cut back some of the longer limbs, as this shrub can handle ‘heading back,’ as this type of pruning is called. Please note that this shrub is genetically programmed to get quite large, and pruning will not prevent this. Be sure the new spot can handle a shrub that wants to grow 8 to 10 feet up and out (possibly more!).

With this in mind, you can consider transplanting the shrub in the fall. I recommend October or later so that you can avoid a hot spell (which may promote upper growth and/or place the plant under stress). When you dig up the root system, retain as many of the roots and their native soil (surrounding them and holding them together) as you can. You will have to cut the deep taproot(s); that is unavoidable. The tiny, thread-like roots are more important to retain.

When you dig the hole, make it big enough to accommodate the soil around the roots as well as a bit of filler. You don’t need to add new soil; simply backfill with the soil you dug out. You may have to water a bit, even in the fall, until our rainy season begins. You don’t need to saturate the roots, but don’t allow them to dry out.

Garden Tip #178

American Horticultural Society Pruning and Training. Christopher Brickell, editor. New York: DK publishing. 1996
This book gives detailed instructions on how and when to prune trees, shrubs, fruit trees, vines and roses. With good basic background information on general pruning techniques, pruning guesswork is eliminated. The book also explains how to do specialized methods of training like turning your hedge into a living sculpture.