University of Maryland Extension

FAQs - Trees Fall/Winter

evergreens covered in snow

photo: Robert Vidéki, Doronicum Kft., Bugwood.org

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My neighbor went around with a chainsaw and removed all the tree roots in his yard that were sticking above ground level. Won’t that make his trees unstable?

Our neighborhood planning group recommends only Leyland cypress for an evergreen screen, but I’ve seen them blow over. Aren’t there some other alternatives?

Some pines in my area are dying.  Lately, I noticed needles on my white pine yellowing and falling off like crazy. Is there a blight I should know about?

My neighborhood is surrounded by woods. I have noticed that a large number of the oak trees are suffering. The leaves are turning brown and falling off the trees. Many of them are completely bare. Is there some type of disease or insect that is killing these trees?

It is late November is it too late to prune my two holly trees?

We have a Japanese maple planted in our front yard. This fall we noticed what looks like a fungus covering 1/3rd of the foliage. The infected leaves have whitish-gray splotches covering them. And then on some leaves, there is a lace-like pattern of holes. Any advice on what to do over the winter and how to prevent a reoccurrence next spring would be greatly appreciated.

Over the holidays a delivery man backed up his truck into the trunk of my beautiful sugar maple. The bark is scraped off on one side. Is there something I should apply to the wound to help it heal?

What is the truth about black walnut trees?  Do they really prevent other plants from growing underneath them and if so what other trees can I plant near them?

This winter some of the trees in my yard were damaged during the ice storm. My white pines have many broken limbs and my arborvitae are bent over. What can I do to save my trees and to prevent this from happening again? 

We need to regrade our property due to a drainage issue. There are oaks and beech trees in this area and I am concerned about adding soil over their roots. What is the maximum amount of soil I can add? Who would you suggest that I speak to about this issue?

My neighbor went around with a chainsaw and removed all the tree roots in his yard that were sticking above ground level. Won’t that make his trees unstable?

If your neighbor removed several roots or a major root on a tree then, yes, probably so.  The tree could become structurally unstable or become infected and weaken or die. The offending roots probably impeded mowing. A better solution is to mulch, grow moss, groundcovers, or other plants tolerant of dry shade under the trees. When planting, one or two inches of topsoil can be added to fill in between roots. Supplement rainfall when there is less than 1” a week until plants are well established because they get massive competition from that tree.   
Above ground roots are common with some tree species, but can also indicate soil erosion, frequent yet shallow watering, or stressed trees coping with compacted soil, all conditions that can be addressed.

Our neighborhood planning group recommends only Leyland cypress for an evergreen screen, but I’ve seen them blow over. Aren’t there some other alternatives?

Leyland cypress grows very quickly, but the trade-off is that the root system can’t always keep it upright in a stiff wind. Homeowners often don’t realize that Leylands grow to 60-70 feet under normal conditions and can reach 100 feet—overpowering many home landscapes. Good alternatives include Thuja (arborvitae), including both Oriental arborvitae or the American arborvitae, known as Northern white cedar.  Cryptomeria (Japanese cedar) or Chamaecyparis (False cypress) are other needled evergreens that provide good screening. Read the tags of any species to be sure you buy a variety whose height suits your needs.  Mix it up with broad-leaved evergreens such as holly or Southern magnolia. Remember that a large planting of a single species is an invitation to diseases and insect pests. A variety of species stymies them.

Some pines in my area are dying.  Lately, I noticed needles on my white pine yellowing and falling off like crazy. Is there a blight I should know about?

The interior needles of many evergreen species turn yellow, then brown, and drop in the fall. This is the normal shedding of 3 to 5 year old needles. On white pine, this shedding is especially noticeable because they only hold their needles one year before dropping them. If they produce a lot of needles one year, then the following autumn they drop a surprising amount. 

If the tree continues to die back, however, and no new growth is visible next spring, there may be other factors involved. White pines do not tolerate drought or saturated soils well, i.e. the past five years in Maryland. Other possible causes of browning are mites, scale insects, borers, etc. Standing dead pines can attract bark beetles that can infest other weakened pine trees, so it is important to determine whether your pine is dying or not.

My neighborhood is surrounded by woods. I have noticed that a large number of the oak trees are suffering. The leaves are turning brown and falling off the trees. Many of them are completely bare. Is there some type of disease or insect that is killing these trees?

There is not one particular insect or disease targeting oak trees, however many of them are suffering from environmental stress. In recent years we have experienced several droughty periods that may have weakened trees in your area. Stressed trees are subject to insects, particularly borers which can be very destructive.  In some areas, oaks were attacked mid-summer by yellow necked caterpillars or orange striped oakworm causing severe defoliation.  Oak trees are able to recover from stressors, but when they are stressed year-after-year they begin to succumb to their problems.

It is late November is it too late to prune my two holly trees?

Hollies are best (PDF) pruned when they are dormant--the bonus being you can use the clippings for your holiday decorations. If you do not get the chance to do it soon, they can be pruned up until March.  Pruning should be finished before they put out their new growth. 

We have a Japanese maple planted in our front yard. This fall we noticed what looks like a fungus covering 1/3rd of the foliage. The infected leaves have whitish-gray splotches covering them. And then on some leaves, there is a lace-like pattern of holes. Any advice on what to do over the winter and how to prevent a reoccurrence next spring would be greatly appreciated.

The primary problem affecting your Japanese maple is powdery mildew which is a fungal disease. As the fungus grows it produces microscopic chains of spores that give infected areas their characteristic white powdery appearance. The optimum conditions for powdery mildew development are warm days followed by cool nights. This is the reason why we often see this disease in the fall on susceptible ornamentals. At this point in time, there is no reason to be concerned and chances are it will not return next season.  However, try to rake up the fallen leaves as best you can. The lacy holes you describe sounds like feeding damage from Japanese beetles which were active in mid-summer. This is also not something to be too concerned about.

Over the holidays a delivery man backed up his truck into the trunk of my beautiful sugar maple. The bark is scraped off on one side. Is there something I should apply to the wound to help it heal?

Examine the trunk to see if there is any loose bark around the wound which should be carefully removed. It is not advisable to apply any type of wound dressing to the damaged area as research has shown that this actually hinders the tree from forming callus tissue. The tree will not grow more bark over the area but will wall off the dead tissue to help prevent decay and insect organisms from entering the tree. Keep the tree watered during droughty periods as healthy specimens have a greater chance of recovery from such an injury.

What is the truth about black walnut trees? Do they really prevent other plants from growing underneath them and if so what other trees can I plant near them?

Black walnut trees produce a chemical called juglone. It is found in leaves, stems, fruit hulls, bark, and roots. Susceptible plants grown in the vicinity of the trees struggle; they wilt and sometimes die. Even after a black walnut tree is removed, the juglone remains active in the soil for many years. Certain plants are more tolerant of the chemical and can be grown in the root zone area of black walnut trees.  These include arborvitae, beech, birch, crabapple, dogwood, elm, maple oak, Eastern red cedar, and Norway spruce.

This winter some of the trees in my yard were damaged during the ice storm. My white pines have many broken limbs and my arborvitae are bent over. What can I do to save my trees and to prevent this from happening again?

While we had less snow this winter the ice storms we experienced caused significant damage to many landscapes.  The first step is to evaluate the damage to determine if hiring an arborist is necessary. When large limbs are broken, trees are near power lines, or if you need to use a chainsaw or climb a ladder to repair the trees hiring an arborist is highly recommended. Smaller, broken branches should be pruned back to the next major branch, leaving the branch collar (swollen tissue at the base of the branch). Check the arborvitae to see if the branches are broken. If the branches are still intact but bent, bring them back upright and support them by tying the branches to the trunk. Check periodically during the growing season to make sure the rope is not growing into the bark. Small trees that have lodged from the soil can be pulled upright and supported with stakes and guy wires. Remove all supports after one season. Other than keeping your trees properly pruned little can be done to protect large trees from snow and ice. Multiple leader trees such as arborvitae and junipers are more prone to being damaged. Next winter before the bad weather sets in support small evergreen trees by tying the leaders together with strips of soft cloth or nylon stockings. Remove the ties in the spring.

We need to regrade our property due to a drainage issue. There are oaks and beech trees in this area and I am concerned about adding soil over their roots. What is the maximum amount of soil I can add? Who would you suggest that I speak to about this issue?

Trees are sensitive to regrading and the addition of soil over their roots. Most tree roots are in the top foot or so of soil and they extend out well beyond the drip line of the tree. Tree roots grow where moisture, air, and nutrients are available.  Adding soil or even deep layers of mulch are detrimental because it reduces oxygen availability and can smoother roots perhaps causing trees to decline over time. It is possible that the addition of no more than a couple of inches of soil will not negatively affect the trees, but this is not guaranteed.  To discuss the health of your trees and the consequences of regrading you should speak with a certified arborist.

Please send us a question at Ask the Experts if you have a tree question you would like answered. Digitial photos can be attached to your question.

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