Questions on: Silver Maples
Ron Smith, Extension Horticulturist, NDSU Extension Service
Q: We are trying to figure out if our silver leaf maple produces pollen. We live in Colorado, where the weather has been quite warm for a couple of weeks. The tree has thousands of budlike brown clusters that look like flowers, but they're hard. They're littering our entire driveway. Do these buds mean the tree is a male and produces pollen? We also have read that female trees produce small seed pods, which I am pretty sure our tree does not. My husband is having allergy problems because of the pollen. (e-mail reference)
A: Unfortunately, the answer is yes. These trees do have the potential to produce pollen. The flowers on the silver maple are referred to as being monecious, which means there are separate female and male flowers on the same plant. If the trees are seedling selections, they tend to sort out as either predominately staminate (male) or pistillate (female). If cloned selections are made by the nursery, then the tendency would be to select trees that are male (nonseed producing), unless the seeds of a particular tree are extremely ornamental and have high market potential. As far as I know, there is nothing on the market that could be practically applied to control the pollen production. I don't like your husband suffering this miserable allergy, but I also don't like the idea of removing an otherwise perfectly healthy, beautiful tree. Any chance there is some benign medication he can take during the brief pollen-producing season?
Q: I saw your page on the Net and am wondering if you could help me. I planted a silver maple by the house about eight years ago. I was dumb and did not pay attention to how close it was to the house. The trunk is about 80 inches around and about 10 feet from the back corner of the foundation. I have had no foundation issues, but I am wondering if I should remove this tree to avoid any issues in the future. Thanks for your help. (e-mail reference)
A: I doubt you will have any trouble with the roots. It is more likely you will have problems with branches overhanging your house. I would suggest contacting an International Society of Arboriculture-certified arborist in your community to have the tree inspected for any potential hazards. To select one in your community, go to http://www.isaarbor.com/findArborist/findarborist.aspx and follow the prompts to find those listed for your community. Be sure to check their credentials and references before allowing any work to be done on the tree.
Q: We have a huge silver maple and a smaller silver maple in our front yard. Every year they seem to follow the cycle of the leaves turning yellow and then falling off. This year, as of Oct. 24, the leaves are still green, but are shriveling and falling off. Why didnít they turn yellow this year? Is this something we should be concerned about? (Minneapolis, Minn.)
A: You have nothing to be concerned about and there is nothing you can do about it. This is just the tree's way of saying that it isn't completely ready for winter. The closing-down process of deciduous trees begins in late summer or early fall with the shortening of sunlight. The weather progresses to cooler nights and bright, clear, dry days. Chlorophyll production is then slowed or ceases and gives us the yellows, reds and oranges we all like. When Mother Nature throws a wrench into this mix through warm nights and cloudy, rainy days, the whole process is thrown out of kilter and the plants are unable to shut down gradually and completely. What then happens is the leaf tissue is killed by the low temperatures, so the leaves fall off or are blown off by the autumn winds.
Q: What are the red egg clusters on the underside of my silver maple leaves? (West Fargo, N.D.)
A: The red blisters you are seeing is a reaction to eriophyid mites feeding and laying eggs in the early spring as the leaves unfold. What you are seeing is a cellular reaction to this activity. It is not detrimental to the growth or health of the tree. Any spray activity now would be futile in controlling or eliminating the mites. By next year, they may be gone anyway if controlled by natural predators.
Q: I have a silver maple that is having problems. The tree is about 18 years old. This spring, it put out a huge number of seeds (it never had seeds before), which I understand is not a good thing. Many of the inner leaves started to wither and die. Any idea what this is and if I need to be concerned? (e-mail reference)
A: This looks like tar spot, which is a fungal disease that occasionally hits silver maples. I suspect the tree has more serious problems because this particular fungus is not lethal to most trees, unless the infection is very heavy. You might want to get a sample of the foliage and send it to the NDSU Plant Diagnostic Lab for analysis. Send the sample to Waldron Hall, P.O. box 5012, Fargo, ND 58105.
Q: We have a silver maple tree that has all its leaves covered with green pimples. (e-mail reference)
A: Those pimples are caused by the feeding activity of a mite that was active as the leaves were unfolding. This activity resulted in a tissue growth response that is cosmetic and not lethal. These harmless pests will disappear with the falling leaves this autumn. If you want to keep them from appearing next year, have the tree sprayed with dormant oil just as the buds are beginning to swell, but before they open.
Q: We have very sparse foliage on our silver maple tree. The tree is about 40 years old and 20 feet tall. The crown of the tree is almost bare. Our neighbor had a silver maple a few years back, but had it removed. We heard that if the removed tree was male-female, it would affect our tree. Is this true? Right now the tree is full of seed pods. A few years ago we checked with a nursery and were advised to use tree spikes as a fertilizer, but that did nothing for the tree. (e-mail reference)
A: The tree is doomed. When it sends out that much seed stock, it is an indication that the tree is in final (or close to it) decline. I would suggest getting it removed as soon as possible so it will not be an eyesore or a safety threat. Tree spikes are about the most useless treatment you can give to any tree. Silver maples are monoecious. That means they have both sexes of flowers on the same plant, so the removal of your neighbor's tree had no effect on yours.
Q: I have a question from one of my neighbors. She has done some landscaping at her farm because of a tornado that went through just west of her house. She has planted silver maple trees, but they are suckering more trees. She has tried putting down landscape fabric, but the suckers push through the fabric. Is there a physical or a chemical plan to take care of the suckering problem? (e-mail reference)
A: Believe it or not, there is a product called Sucker-Stopper RTU. If it is not available locally, she should be able to find it on the Web. Cut the suckers back and then spray the surface of the cut. It usually works for the entire season. While some suckering is to be expected, usually heavy suckering is a symptom of the tree being planted too deeply or under some kind of stress. You might check for these two possibilities.
Q: Two years ago we bought a house with a beautiful silver maple in the backyard. We needed to put an addition on the back of the house and took extra care to try to protect the tree. We laid down 24 inches of mulch to protect against construction traffic. The tree seems healthy, but I have noticed this spring that a few smaller branches are without buds. What should I be watching for to make sure this tree stays healthy? Is there anything I should do to help it along? (e-mail reference)
A: Look for major branch decline, which is called crown decline or dieback. Get a core aerator and aerate your entire lawn area where the tree is planted. This will help get air to the roots in case the soil was compacted during construction.
Q: We have a silver maple that is doing fine, but has an irregular shape. The branches in the center of the tree have not grown as fast as those on the bottom and top. Is there anything that can be done to even out the shape of the tree? (Moorhead, Minn.)
A: Yes, contact a professional tree service to inspect the tree. The professional can give you pruning suggestions or can do it for you.
Q: Someone told me that silver maples are notorious for clogging septic drain fields. Is that true? How close is too close? Should I move a couple of silver maples that are within about 20 feet of my drain field? Any recommendations for better trees near a drain field? (Grand Forks, N.D.)
A: Silver maples get a bad rap for too many problems. What tree wouldnít invade a septic drain field with its roots? It is like putting freshly baked chocolate chip cookies in front of a kid (or salivating adult) and saying ďdonít touch!Ē Definitely move them to about double the distance. Another solution is to install a biobarrier around the drain field to keep roots from penetrating. Donít give up on your silver maples yet because they grow fast, which everybody wants. They also have nice fall color and are handsome trees, if allowed to mature with proper care and pruning.
Q: I have a question about a silver maple tree that was planted a few years ago on the south side of our house. It is growing, but the leaves are always pale yellow green and they dry up and fall off in late summer. It doesnít seem to follow the other silver maples in the area. What can I do to green up the leaves and keep them on the tree to turn color and then fall at the proper time? Thank you. (Moorhead, Minn.)
A: You very likely have a seedling selection of silver maple that is not tolerant to the alkaline soil in our region. You can try fertilizing with an iron-based fertilizer to see if that corrects the problem, but in more cases than not, it is a futile effort, with the tree eventually dying or needing to be cut down. If you replace the tree, be sure to purchase a named cultivar, such as northern acclaim thornless honeylocust. This and other named regional trees have been tested for tolerance to our environment, including the cold, heat, disease, insect, and soil conditions.
Q: We have a fair share of silver maple trees. I have one nice specimen next to the house. A month ago I noticed a woodpecker on the side of the tree and didnít think twice about it until a couple of weeks later. This little pest has punched about a dozen holes in the tree and now the tree is bleeding. The sap is running down the tree to the point itís foaming at the base. How do I stop the tree from bleeding? I am concerned this will destroy one of my nicest trees. I did a close inspection of one of the injuries and itís deep into the meat of the tree. (e-mail reference)
A: Spread Tanglefoot where the bird is working or wrap it in aluminum foil. Both will discourage the woodpecker from returning. The tree should heal itself without trouble if it is otherwise healthy.
Q: Last year we lost our silver maple. The city planted a red maple to replace it. We have clay in our soil, so I put two tree spikes around the tree. It has some yellow leaves and some of the branches on top are partially bare. I have noticed no new growth. I see other young trees in the neighborhood that are slowly losing their canopies, so Iím worried that our tree is dying. (e-mail reference)
A: The only assistance I can give you, with the information provided, is to get in touch with the city forester and have them inspect or replace the tree. Throw out the tree spikes because they are a waste of time and effort.
Q: I planted a silver maple in my backyard in mid-April. I believe it is a silver queen. It had a few leaves on it when it was planted. It did not produce any more leaves and now the existing leaves are dead. Some of the small branches seem very brittle. Any ideas? (Fargo, N.D.)
A: Planted too deeply? This is a good cultivar that is adapted to our area. Take a branch to the nursery where you made the purchase to see if they can help you.
Q: I am thinking about planting mature silver maples. What should I look for? For example, would a 6-inch diameter tree be too large? (E-mail reference)
A: Forget the mature ones, they are expensive and don't transplant well. I would suggest planting something in a bushel or 10 gallon container. They grow quickly and you can appreciate their growth.
Q: My 3-year-old silver maple has yellow leaves with brown edges and spots. The leaves turn brown, crust up and fall off. The nursery said the tree needed iron so I gave it iron twice but that didnít help. The tree produces new leaves so I don't think it's dying. (Fargo, N.D.)
A: The nursery is correct. Most silver maples, especially the seedling selections, need supplemental iron. It will not correct the iron deficiency symptoms that have shown up already, but the new growth should be free of it. You can do direct foliar applications that don't last as long or you can inject it into the root system. Both approaches are effective. This is a physiological problem known as iron chlorosis. The pH of the soil is so elevated that iron becomes unavailable to certain species of plants. Silver maples are very sensitive to the problem. They need to monitored on a regular, timely basis. If it is allowed to get out of hand, the tree will eventually die.
Q: I have silver maple trees on my boulevard. My neighborís silver maples have small clusters of little reddish-green nodules on many of the leaves. Could it be spider mites? (E-mail reference)
A: Itís nothing to worry about, just enjoy the changing sight. The growths are from what are called erythroid mites that were active in the early spring. Their activity has a plant cell stimulation effect on the tissue, which causes the nodular growth. The damage is only cosmetic and there is nothing you can do to control them. Next spring they will very likely be completely gone.
Q: What is the average life expectancy of a silver maple under normal conditions? I have a large one hanging over my house. Itís old so Iím wondering if it's time to cut it down to prevent damage to my roof when it collapses. (E-mail reference)
A: I don't like questions like this. Age has very little to do with the life expectancy of any tree but you are right to be concerned about it collapsing on your house since it is so close. I strongly advise you to contact a certified arborist to do an increment boring of the trunk to find out what shape the tree is in. The arborist may also possibly do some selective pruning. Base your decision on the information that is provided rather than on average age. You will be able to sleep better at night.
Q: I am planning to purchase a home with a large silver maple in the back yard. Close to half of the major branches have no leaves. The others branches have normal looking (from 30 feet below) leaves. I know this is not a lot of information, but does it sound like the tree is dying?
Also, I have noticed several silver maples in town with a yellow tinge to their leaves. I assume this is unusual for the middle of summer. Is there some pest or disease that is affecting silver maples in the Fargo area? (Fargo, N.D.)
A: The silver maples in the Fargo area typically suffer from iron chlorosis due to the high alkalinity of our soil. If you are considering the purchase of the home based on the tree, then I think you will be disappointed when the tree completely expires in a year or so. Silver maples can be beautiful trees if cultivars for our region are selected. Cultivars such as 'Northline' and 'Silver Cloud' are from the Canadian prairies and will certainly develop and outperform any seedling non-cultivar that might be planted in our region. Keep those names in mind if you purchase the house and end up having to take the tree out.
Q: Last year I noticed lumps on several leaves of our silver maple tree, but was able to pick them off or I removed the leaf. This year is much worse. Is there something I could spray on the tree, as it is only 3 years old. I also noticed there are no leaves on many of the upper branches. Could this be winter kill or something related to these lumps? (Hillsboro, N.D.)
A: The bumps are nothing more than cosmetic swellings from the early spring and feeding of a mite. It will not harm the tree, nor was it the cause of the dead branches in the upper part. Most likely, that was the result of our fickle winter weather!
Q: In our front yard we have two silver maples between 30 and 40 years of age. The root system is a problem in our yard. We have a small yard and half of it is taken up by roots. Our driveway is cracking and the trees are about 20 feet away from the house. We have to remove them. One company will pull the stump and roots and put top soil back. Another company wants to grind the stump and roots, then remove the shavings. We were thinking of having them ground instead of removed because of the cost. Is it a wise choice? Or will we be filling holes for years to come? (E-mail reference)
A: It all depends on the contractor. I have seen many successful grind-out operations where a quality landscape could be developed after the removal. I would ask the contractor if he can supply you with the address of some past clientele for your reference. If he refuses or cannot, then a red flag goes up as far as I'm concerned. The grinding would be less destructive an operation so should cost less, but you need to see first hand the quality of this person's work before making a commitment.
Q: I have a large silver maple, about 35 years old, in my back yard. It is preventing any sunlight from getting to a large area of the yard and some branches are resting on my buildings and my neighbor's. I would like to have major pruning done that would remove about a third of the tree's branches. What time of year should this would be done? (Detroit Lakes, Minn.)
A: Silver maples and other large trees are best pruned in the late winter or early spring. Maples have a propensity to "bleed" sap when cut at that time. Don't let this concern you; the tree will not bleed to death. Pruning now should be confined to anything that could be a threat to property or bodies. Pruning cuts this late in the season will not have a chance to heal properly as they would in the early spring.
Q: We recently bought an 11- year-old house replete with several silver maples in the front and back yards. The roots running across the ground make it difficult to mow. Is it safe to cut the exposed roots? I assume that the trees are around 10 to15 years old. (E-mail reference, Huntsville, Ala.)
A: The exposed roots help to anchor the tree, but usually the silver maple is not short of roots, so those intersecting the surface can be cut back. Usually if a tree is going to windfall it will do it no matter how extensive the root system happens to be. I'd also suggest getting some of the canopy thinned out to reduce the exposure and resistance to wind forces.
A: How old myths die hard! The silver maple has problems as all trees do, but foundation destruction and getting into drainage systems are not two of them. Tree roots will follow the path of least resistance, and where a balance of nutrients, water, and air exist. Any tree roots will enter the drain tile that leaks. In the "old days," about this time in the last century, drain systems were in fact made up of ceramic tiles, which could shift and crack, allowing the fluid which many tree roots found to their liking to seep into the soil. The roots then entered the tiles themselves and plugged them. When this became commonplace, the Roto-Rooter Man became popular and a new service industry thrived. Nowadays, the Roto-Rooter Man cleans drains not of roots, but lint and other stuff that seems to back up in some of our drainage systems. Let the trees live! They will mature and shade part of your property as well as your neighborís. Enjoy their silver-backed foliage and beautiful fall color.
A: I suggest a tree surgeon come out and take an increment boring of the tree. This will determine the soundness of the trunk and whether or not it is a potential threat for windfall in a storm. In some cases, the tree does not need to be removed; in others, it is best removed immediately. A competent, ethical tree surgeon will advise you properly. Just don't delay having it checked for safety's sake.
A: Weed and feed applications are a pet peeve of mine for just the reason you are concerned about. I wish the stuff was banned! Evergreens generally donít need a lot of fertilization. Simply spray with Miracle-Gro when new growth is taking place once a year, if you feel there is a need.
A: The problem is likely a canker disease that has girdled the branch that appears dead. It could also be borers, but the likelihood of it being a canker is greater. Only a diagnosis can tell for sure. When something like this occurs, it is difficult to turn it around and still have a decent looking tree. I suggest getting an arborist out there ASAP for an accurate diagnosis and assessment.
A: If you got seedling silver maples, they may be right. If you planted named cultivars like McKay's Seedless or Silver Queen, you'll probably get the dependable fall color you are looking for. If you just planted the seedlings and not the named cultivars, and the fall color is important to you, AND you want to please your neighbors, then take them out and select one of the many cultivars of red maple. Everybody will be happier then.
A: My advice is to get a tree surgeon or an arborist to determine the extent of internal decay. Properly cared for, this tree could be an asset to your property; ignored or neglected (as you indicate it has been) it can be a liability -- and a deadly one at that, depending on location. Arboriculture and tree surgery are not trivial pursuits. Qualified arborists and tree surgeons spend years learning about their profession in a combination of higher education and field experience. The arborist could use a borer to determine the soundness of your trees, perform proper cavity repair, pruning etc. Your situation, unfortunately, is an example of what an improper pruning cut carried out years ago can result in.
Q: We have a very large, old maple tree that takes up most of our back yard. This year the leaves have masses of small bumps on them. Some are bright green and some red. Is this something we need to be concerned about? (e-mail)
A: Not a bit to be concerned about! The tree is likely a silver maple and the bumps are the result of mite feeding earlier in the season. So enjoy this harmless, interesting wonder of nature.
Q: We transplanted a tree that we think is an ash tree. Can you tell me why it has bumps on most of its leaves? I am also wondering if I was correct when I moved my spruce tree out from under this ash tree. (Montrose, S.D.)
A: The leaf samples you sent in were from a silver maple, not an ash tree. The bumps are actually tissue galls, caused by feeding in the earlier part of the season by very small mites. Their damage is cosmetic, not lethal. No control is necessary or practical.
You were right in moving the spruce from under the shade of this maple tree. Sprucemost evergreens, in factdon't relish shade. Your small spruce should thrive in a fully sunny location.
Q: Can you tell me why the enclosed leaves from my silver maple tree are turning prematurely yellow with brown edges? (Glen Ullin, N.D.)
A: Your silver maple is a seedling selection which is showing an intolerance to our alkaline prairie soils by producing chlorotic (low chlorophyl containing) leaves. You can try fertilizing with iron sulfate or chelated iron to see if it will pull out, but I sincerely doubt it. This affliction is usually progressive until the tree dies.
Sorry about the bad news!
Q: Enclosed is a sample leaf from a tree that was planted in my back yard in the early 1980s. I know it is a maple, but I would like to know what kind. I have been trying since then to find another maple tree exactly like it, but I haven't had any luck. The one that was planted grew fast, and the ones I have found are slow growers. (Jud, N.D.)
A: It is a silver maple. Try one of the cultivars such as Blair or Silver Queen. They usually do better than seedling forms
Q: Can you tell me what is growing on my silver maple leaves? I have been told it is harmless, but I'm still not sure. (Devils Lake, N.D.)
A: You received the correct advice. It is the harmless erineum gall. These are caused by mites in early spring. They come and go; there is no need to spray.
Q: Can you tell me what is wrong with my silver maple tree? (Napoleon, N.D.)
A: Your maple is suffering from a number of maladies: iron chlorosis (severe), tar spot, anthracnose and mite damage. At this stage, I'm afraid there isn't much you can do. You may want to attempt the following: core aeration starting at the dripline (canopy edge) and going concentrically out 10 to 15 inches, spreading of sulfur over area aerated, and watering in completely. Apply sulfur at a rate of 35 pounds per 1,000 square feet. This will help lower the pH and may improve the health of the tree by making more true elements (like iron) available.
Q: We recently bought a home in Pelican Rapids and one maple tree (8 feet) has this on it, and is getting worse. Our other maple has nothing on it. We have no idea what it is or what to do about it. Please advise! (Pelican Rapids, Minn.)
A: Your silver maple has bladder galls, one of the more famous galls caused by mites. Their form and color, as well as their high population on maple leaves, cause much concern for homeowners. These mites migrate to the unfolding leaves where they begin to feed, causing the pouch-like galls.
To make a long and interesting story short, you have nothing to worry about as they will not harm the tree, and there is nothing recommended for their control.
Q. This is a leaf from a silver lustre maple. The tree is about 8 to 10 feet tall, just a stick with leaves on the top half! The nursery planted it for me and I water it a lot. Will it make it through the winter? What should I do, if anything? (Huron, S.D.)
A. Have faith! Mother Nature works hard to help the members of the plant kingdom survive our sometimes clumsy efforts to reorganize the setting we live in. I feel confident the nursery did a good job at planting and you a good job of post-planting care. It should pull through the winter OK. Do nothing more.
Q. Help! What is happening to my silver leaf maple? I just discovered this stuff on the leaves. What will it do the tree and what can I do?
Your column is required reading every Friday. Thanks. (Hope, N.D.)
A. Nothing to have a heart attack or even an upset stomach over. They are simply mite gall formations and are nothing more than a cosmetic affliction with the plant.
Since there is nothing you can do now, you might just as well enjoy observing them. Since the activity that forms the galls takes place at leaf opening, it isn't worth fussing over, as the elements and predators could reduce the population better than eiher of us could.
Required reading? I'm impressed. Thank you.
Q. I have written to the Hortiscope before and have received great help.
We now have trouble with a young maple tree, planted beside our driveway. The leaves on the west side are drying up (see the enclosed sample). What could be causing this? I think the small oval leaves may be hail damage. Also, we planted a Marshall seedless ash two years ago. This spring we noticed the bark on the trunk and branches are cracked open. We would like to know the cause and what to do to save this tree.
We do not get the paper, so could you please send us a letter. Thank you. (Mobridge, S.D.)
A. The damage in all cases is abiotic or nonpathogenic. The silver maple leaves look as if they have been exposed to excess heat from an engine or blacktop driveway surface, possibly exhaust fumes.
The Marshall ash responded to the winter sun. Protect this year with tree wrap or white-wash.
Q. I am sending a sample of my silver maple tree. It was planted in the spring of 1980. What is this stuff that is invading this tree? It started three years ago. I root fed it with an insecticide, but it didn't help. Some of the leaves fell off. What can be done?
I like to read your Hortiscope. Thanks very much. (Wishek, N.D.)
A.Your silver maple has lots of company this year and there is nothing anyone can do at this time. Consider it an invasion of the maple bladder gall mite.
They begin their feeding cycle as the leaves unfold, which is when they should be sprayed with either a dormant oil just before bud break, or right after the buds have opened with a miticide.
Frankly, I would do nothing as their activity is not lethal to the tree and the normal cycles of nature appear to bring them under control.
Q. Can you identify what is on the enclosed maple leaves and what can be done about it? Thank you.
Enjoy your column in the Peddler. (McVille, N.D.)
A. You sent me an excellent example of damage from bladder gall mites. These green, warty protrusions on the foliage of your silver maple will later turn blood red.
Generally, these critters come and go and spraying is not necessary. At this point, there is nothing you can do, but if you wish to attempt control, spray with dormant oil in the spring just before the buds open.
In the meantime, sit back and observe the changes over the remainder of the growing season.
Q: I planted four silver maple trees from the same group at the nursery a year ago this spring. This year when they leaved out, three got nice green leaves, but one has reddish, rust-colored leaves. Is something wrong with the one tree? (Wing, N.D.)
A: It's probably just different genetic variations existing amongst the individuals of the species. If that one does keep its red leaves, let me know. It may be something we could clone and introduce to the public!
Q: We are having problems with our young silver maple trees. We trimmed the 3-year-olds last year because they were growing branches all over. We cut off the lower branches to make the trees grow straight, not crooked. This year, neither the 2-year-olds nor the 3-year-olds have any leaves on them, and they are growing shoots out of the bottom. We also planted some green ash trees at the same times and they look fine. Do you have any suggestions as to what is wrong or is this normal? (Wessington, S.D., e-mail)
A: It sounds like you got ahold of a seedling selection that did not originate from your geographical region. Seedlings coming from regions of the country south of your location may not survive the winters or those trees might be teased into or out of early dormancy or early bud break by a different day length. I suggest cutting or digging out the roots that are now suckering on you. Sorry for the bad news!
Q: I have a silver maple (20-30 yrs old) that drops a few discolored leaves most of the summer. These leaves have a scab on them. Other than this condition, the tree appears healthy, turns proper color in the fall and buds and leafs out normally in the spring. Can you enlighten me on this condition? (E-mail reference, Ellendale, N.D.)
A: There are fungal leaf spot diseases that hit many tree species at sub-lethal levels each growing season, causing leaf drop on the older leaves. I don't know whether or not it is worth the effort on your part to eliminate this since it poses no threat to the health of the tree. It's kind of like us catching a cold -- little harm done -- and your tree apparently has good resistance to this pathogen to keep it from becoming virulent and destructive. Normal fall sanitation -- picking up of leaf litter -- every fall sometimes does the trick, as well as a spray of lime-sulfur in the early spring before leaf out. This often kills the overwintering pathogen that is taking up residency in the bark tissue of the tree. In addition, keep an eye on the tree for dead twigs and branches, remove them when noticed, and try not to allow the tree to become drought stressed during the season. Water well once a week when rainfall is lacking.
Q: My parents have a young silver maple tree planted in their front lawn, currently about 8 feet high. While they are aware that a silver maple is not a "bush" type of tree, they are wondering if by cutting the top off the tree would then "bush out" instead of continuing to grow upward? (E-mail reference, Virginia)
A: I don't like the idea of "topping" a tree, especially one with opposite leaf bud arrangements like maples have, as it is difficult to get directional growth in such a case, as compared to a tree like an oak, for example, that has an alternate leaf bud arrangement. A bushy type tree that would be a better selection is either an Amur maple or Tatarian maple. These generally come with a multi-stem arrangement that allows them to be more spreading in character than simply upright. Silver maples are naturally a single stemmed tree that typically develop into a loose, oval form at maturity. Silver maples typically have a weak branching system, so we try to encourage proper pruning to help compensate for that shortcoming. A topping pruning procedure would only exacerbate the problem further. Allow the tree to grow naturally with a minimum of corrective pruning, or replace it with one that will have the form that you desire.
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