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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: Phormium, Hebe, Effect of storms, Lavandula stoechas, Pruning

How should I prune winter-damaged Phormium, Hebe, and Spanish lavender? The Phormium leaves look wilted. They are folded over and discolored but not blackened. The Hebe 'Autumn Glory' and 'Great Orme' are blackened, while 'Shamrock Purple' is mostly brown. The Spanish lavender has some blackened foliage, but mainly just got weighed down with snow.


My advice for right now would be only to prune any branches which were broken under the weight of the snow. We may yet have more cold weather, so you don't want to make your plants any more vulnerable.

You may want to wait until early spring or at least all danger of further frost or snow and ice to prune your Spanish lavender (Lavandula stoechas). Under normal circumstances, Spanish lavender can be pruned back by a third to one half in early to mid-autumn, according to Lavender: The Grower's Guide by Virginia McNaughton (Timber Press, 2000). I grow Spanish lavender, and I usually tidy the plants a bit when most of the flowering is done. However, because of the extreme cold to which your plants were exposed, you may want to assess them in spring, and prune out any dead areas, or replace any mostly-dead plants.

I recommend giving the Hebe plants a chance to recover. I have heard of very sad looking Hebes coming back, perhaps not the first summer, but by the following year. By mid- to late-spring, you should be able to tell what is truly dead and prune it, though Hebes sometimes dislike hard pruning. The Hebe Society of New Zealand suggests pruning frost-damaged shoots in spring.
An article in the Kitsap Sun from May 2011 by Kitsap County Extension agent Peg Tillery mentions hard-pruning winter-damaged Hebes which manage to recover.
You may find this information from Oregon State University useful, as it evaluates the cold hardiness of individual species of Hebe. Here is an excerpt:
"Major cold damage will cause browning of most of the leaves on the canopy, followed by dieback. Sometimes, plants will recover over a 2-3 year period from this damage if subsequent winters are mild. Very severe, sudden cold often turns the entire plant brown and sensitive cultivars do not recover from this damage and require replacement."

There is a discussion of winter-damaged Phormium in GardenWeb, an online gardening forum. Again, I suggest waiting until spring to see if only parts of the plant are dead. Keep in mind that gloves are essential when pruning this plant!

The Oregonian has an article about the effects of the December 2008 cold and snow on tender plants. Here is an excerpt:
"I hope, unlike me, you've had better luck with your phormiums surviving the storms. Not to be negative, but chances are you didn't. On the positive side, though, they'll most likely only die to the ground. If you cut them back, phormiums often come back from the roots."

Date 2017-08-15
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Plant Answer Line Question

Keywords: Effect of storms, Soils

We had quite a lightning storm today, and it made me think of something a friend had told me. He used to farm in Eastern Washington, and he said that lightning was good for the soil and the crops. Is this pure folklore or does it have some scientific basis?


This isn't just folklore. According to the Indiana Public Media's Moment of Science, "there is enough electrical energy in lightning to separate the nitrogen atoms in the air. Once the atoms are separated they can fall to earth with rain water, and combine with minerals in the soil to form nitrates, a type of fertilizer."

Date 2018-04-04
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Plant Answer Line Question

Keywords: Effect of storms, Pruning, Conifers

There's a self-described tree service knocking on doors in my street, trying to get people to pay them to do "wind sail reduction" on their trees. My neighbor just agreed to have them prune 17 of her conifers. Bad idea, right? Can you point me toward resources so I can dissuade her from going ahead with this plan?


Yes. The Washington Department of Natural Resources published an article, "Trees Don't Wind Sail, Do They?," in their online newsletter, Ear to the Ground, 12/20/2011. Here is an excerpt:
"Some people claiming to be tree experts will tell you that 'wind sailing' is a great way to protect your trees from wind damage. You may have heard this fabricated notion of thinning limbs from trees in order to make them stable during wind storms. This improper pruning technique is promoted to supposedly make trees safer in the wind by allowing wind to pass through the canopy of a tree, thus reducing movement and strain on a tree. Not so!
"This may sound reasonable and may even seem to have some logic behind it. But beware--the truth is, there is no scientific study that shows thinning is wise or safe way to decrease resistance during a wind storm. "Actually, many studies have shown that the outside limbs can divert some wind from the center of the tree and act as a buffering shield. Aggressive thinning, on the other hand, can make the remaining branches more vulnerable to failure; left isolated, these limbs must take on the elements alone. Pruning out a major portion of a tree's canopy for the sake of staying upright during a wind storm harms most trees in the long run."

The DNR has another, similar article from 12/6/2012 in their Tree Link News entitled 'Windsail Reduction:' A Northwest Controversy.

You can also suggest that your neighbor speak to someone at Plant Amnesty, a local organization dedicated to teaching the community about proper pruning techniques (as well as informing them about ill-advised methods!).

Date 2018-03-14
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May 31 2018 13:14:08