Questions on: Red Maples

Ron Smith, Extension Horticulturist, NDSU Extension Service

Q: We have a chance to buy a couple of red maples, but the leaves are green. Are they really red maples? If so, will the leaves eventually turn red? (e-mail reference)

A: The red maple species, Acer rubrum, will have green leaves during the summer, but have outstanding red coloration in the fall.

Q: I have two autumn blaze red maples in my yard. The first year, the leaves turned a glowing, fire red, which was beautiful. Since then, the leaves have turned from green to brown. I don't know what to do. During the summer months, the trees get full, dark green leaves. Do I need to use a special fertilizer? (e-mail reference)

A: You know the tree has the genetic potential to turn the colors you like because you’ve seen it. Fall color on a tree is dependent on many factors, such as shortening days, temperature variations and clear, crisp, sunny days. Couple this with a little water stress and you should get your colors. Beautiful fall leaves sometimes fail to show up on turf-planted sites because the lawn receives a nitrogen fertilizer three or more times a year, so there is no nutrient stress on the trees. If the tree is getting water through a lawn sprinkler system, you may not get the beautiful colors because the tree is not water-stressed. If the fall is warm, cloudy and rainy, you will get no or very poor fall colors. In other words, normal environmental stresses will produce the best fall colors!

Q: We bought a red maple tree last fall. It was staked, but with new growth it could hold its own. The last couple of months we have been fighting bees, flies and tiny ants that love the leaves. At this point, the leaves are green, but the tips are brown and dry. We see no other visible sign of stress, but some of the leaves have tiny spots on them. We apply Sevin, Daconil, fertilizer and water, but not daily. (e-mail reference)

A: The swarming insects were attracted to the honeydew the spider mites were producing while feeding on the foliage. That would account for the small spots you are seeing on many of the leaves. The brown tips could be the result of the high temperatures we experienced this summer. It also could be an indication of overwatering or applying the insecticide or fungicide during the hot spell. It also could be a result of too much fertilizer being applied. Keep the soil moist, but not soggy. Stop fertilizing and applying insecticides, especially Sevin. Also, quit using fungicides. The tree should recover nicely, if you follow this basic advice.

Q: I had a landscaper move a Japanese red maple tree about 10 feet. It has been a week and the leaves are starting to dry up. I was told to give it lots of water and I used some fertilizer tree spikes.When we moved it, we made sure the hole was big enough, but not too deep. The landscaper filed the hole with soil and put mulch on top. The landscaper told me not to worry because the tree is in shock, so I was told to keep watering it and the tree would come back. Is there anything else I should do? Should I water the tree daily, twice a day or every other day? Should I be using anything else? (e-mail reference)

A: Don't overwater the tree! Soaking the tree once a week is fine in most instances. The objective should be to keep the soil moist, but not soggy. Forget the fertilizer spikes because they are a waste of money. It remains to be seen if the tree will recover from the move. Ideally, it should have been moved while it was dormant, not freshly leafed out.

Q: The red maple tree I have is overgrown. Is it harmful to prune it during the winter months? (e-mail reference)

A: Not at all. In fact, late winter is the best time to carry out deciduous tree pruning because it is easier to get to the branches that need pruning, you have better working temperatures, no biting bugs and there is less chance of disease spread. I would wait until mid-February to do it.

Q: We planted a red maple in our backyard last fall. The tree has done well until now. The leaves started turning red and are now falling off the tree, especially at the top. My husband took a sample to the nursery where we purchased it. They said it has been overwatered. We have received a lot of rain this year, but have not watered it when it has rained. Our backyard is on a hill, so there has not been any standing water around the tree. Will our tree die, or will it come back with drier weather? (e-mail reference)

A: The nursery made a quick diagnosis without knowing enough facts. It could have been getting too much water, but it is unlikely from where you say it is located. Another possibility is that it is planted too deep. The root ball should be even with the soil surrounding it, and with no more than about 1 to 2 inches of mulch (if any) around that area.

Q: Last year I received two trees as a gift. We planted one on the west side of our home and one on the east. This spring they both set wonderful leaves, but now all of a sudden the one on the east side has a wilting appearance. The leaves have turned a pale green to light yellow with brown/black spots. Some spots seem to have a light center that looks like an eye. The vines of the leaves are dark green, but some are turning brown. Also, the branches and trunk seem to have a bright orange color where the other tree is still green/brown looking. Is this a problem that is treatable? We also had a large very old red maple that was taken down when we built our home because part of the tree was dead. I am now wondering if there is a problem with the soil. Are these trees adapted to our area? (Hartland, Minn.)

A: The red maple is adapted to most Minnesota conditions; however the situation, as you described, doesn’t sound good for the tree. Something is killing the tree and only an on-site diagnosis can determine what it is. It sounds like a combination of rust fungus, chlorosis and a leaf-spot disease. Since the tree is so young, I would simply remove it and replant in another area. There might be spores from the removed tree still in the soil.

Q: We have a red maple that until this spring seemed perfectly healthy. Half the tree has failed to fully leaf out. The branches budded and tiny leaves appeared, but did not fully develop. The other half of the tree looks fine. Someone said it might be root girdle. Do you know anything about this? (e-mail reference)

A: That someone could be right. Carefully dig down on the side of the tree that is showing the symptoms you describe to see if there is a girdling root. If there is, take a hammer and chisel and carefully cut out the offending root. The tree should recover if that was the problem.

Q: I planted a Northwood red maple two years ago as a bareroot tree. The first year it seemed fine, but really didn't do much and the leaves seemed a little pale. This year the leaves opened, but are noticeably yellow with a thin line of green along the veins. Some of the leaves are turning brown. Any idea what its problem is? (e-mail reference)

A: It sounds like a classic case of iron chlorosis. Try to get some iron-containing fertilizer or chelated iron and apply it to the root system. This may correct the problem if it isn't too far gone or the pH of the soil isn’t excessively high.

Q: My husband and I purchased a red maple in June. I watered it when we delivered it home. The next day the leaves on that side looked wilted and dying. Please help with a solution to this problem. (e-mail reference)

A: How was the delivery made? Was it hauled in an open bed truck or with the branches hanging out of the trunk of a car? Both could cause the wilting you describe. In many cases, the tree will recover, but look bad during its initial growing season.

Q: Could you tell me why my red maple tree has round holes in some leaves? It has been in my front yard for about six years. (e-mail reference)

A: It could be cutter bees. The damage shouldn't be extensive and the bees don't hang around for long. If the problem continues, to the point where it appears that it may impair the health of the tree, look for the culprit and initiate some kind of control once the offending insect has been identified.

Q: I planted some red maples in my yard this spring. Since then I’ve read that red maples are poisonous to horses. Do you know anything about this? (Pierpont, S.D.)

A: Not knowing the answer, I checked my poison plant book by Kingsbury. Sure enough, on page 216, it states: "Two cases of death in livestock, involving cattle and horses, after eating maple leaves have been reported from West Virginia." Based on that, I would either remove the trees or certainly keep the horses away from them.

Q: I've just purchased a house that included a beautiful full red maple in the back yard. I do not know how old this tree is but I noticed a powdery substance on the leaves. Some leaves turned brown and curled. Can I save it or is it doomed? What do I use to spray it with if the tree is taller than my house? (E-mail reference)

A: You don't want to attempt to spray the tree or do a self diagnosis. Make contact with an International Society of Arboriculture Certified Arborist to have the tree inspected and sprayed with the appropriate legal material.

Q: I have a question about autumn blaze red maples. I recently planted four of them in my yard but I just read they are a hybrid of red and silver maples. I’m wondering if the roots will run on top of the ground like a regular silver maple, which is a pain to mow over. If so, mine are coming back out of the ground before they take hold. (E-mail reference)

A: I have never seen an autumn blaze maple that has produced a serious surface root system. You should be home free unless you have dense clay or soil that is highly compacted.

Q: This spring I planted a row of seven poplar trees, a row of 35 Lilacs, a row of 15 sumac and a grouping of three red maples. All of the plants came from our county Soil Conservation Service. I've made about 20-24 inch diameter rings to hold mulch out of thick plastic edging for each tree or bush. They all seem to be doing very well. I’m almost finished putting plastic and rock on top of each row to prevent any grass or weed growth in between the trees. I mulched heavily inside each ring with cypress mulch and water thoroughly once a week if we don't get rain. The trees and the landscaping all look great but are there any problems that the plastic and rock could cause? Is there anything else I should do to keep them healthy? (Lisbon, N.D.)

A: It sounds to me like you’ve given the project a lot of thought and done a lot of work to get these plants established. If you haven't overdone the mulch around the plants (greater than four inches), they should be ok. It certainly will not be your fault if they don't turn out beautifully!

Q: I have a red maple that is ten years old. It has developed cracks on one side of its trunk, about five to six feet up from the base. It seems that, right above these cracks, branches are dying. The rest of the tree seems fine. What do you think is happening? (E-mail reference)

A: Those cracks are likely frost cracks that have affected the immediate branching area of the tree. Clean the wounds carefully back to the attached bark and allow them to be exposed to open air. Gradual healing will begin taking place. This fall, wrap the trunk in kraft paper right up to the first branches to prevent it from happening again. Red maples are prone to this problem until they develop a thick corky bark.

Q: I have a red leaf maple that we planted three years ago in our small yard that is in the middle of a forest. The trunk is 5 inches in diameter and about 15 feet tall. The tree seems to be growing taller than wide with one branch rising above the rest. Should I trim the top branch to promote wider growth? Is this due to the height of the surrounding trees? (E-mail reference)

A: Surrounding trees will impact your maple. A maple’s natural form is a rounded so go ahead and prune to meet your needs.

Q: I have a red maple that I planted three years ago. It developed a large cut in deep enough to see the core of the trunk. I wrapped the gash and weeks later a similar yet different shaped cut appeared above the wrap. This one is only about 1/2" wide and swirls around the tree for approximately 6 inches. The rest of the tree appears very healthy. There's tons of new growth this summer. Am I infested? What am I to do? (E-mail reference)

A: Red maple trees are notoriously thin-skinned in their early years. I would suggest a full trunk wrap until some corky tissue begins to develop. Also, resist any unnecessary pruning, as this often exposes new trunk tissue to sunscald problems. Eventually, everything should heal as the tree matures. Simply keep it growing vigorously.

Q: Each spring I do a little pruning on my red maple at the lake. I understand that I can take an 8-inch cutting from a pruned branch, dip it in rooting hormone, secure it in an environment that will support the cutting, keep it moist and warm and mostly shaded for 45 to 60 days, and the cutting will take root in time for transplanting and establishment in the ground before fall freezing. If this is so, is there a certain technique to use, a certain "strength" of rooting hormone, a certain rooting medium to use, any certain care to take to propagate this beautiful tree? Any information would be appreciated, as I plan to propagate red maples in both Minnesota and North Dakota. (E-mail reference, Fargo, N.D. and Devils Lake, Minn.) 

A: You are correct; red maple will root from cuttings and grow into beautiful trees. Here is what Dirr, the woody plant guru of North America, suggests: use only healthy, firm wooded stock, with mature leaves, that have either a single or multiple nodes, dipping them into a 5000 ppm (parts per million) IBA in 50% alcohol, 50/50 peat/perlite, apply mist evenly and without fail, and cuttings should root in three to five weeks. IBA is a synthetic rooting compound known as idolebutyric acid that stimulates the formation of adventitious roots, which is what you want to do. This is diluted in alcohol -- the rubbing kind, not the drinking -- and the stump ends are dipped into the solution prior to sticking into the rooting medium. The use of bottom heat always helps speed things along, so I would add that to his suggestions as well.

Q: I have enclosed a sample of my red maple's leaves that are starting to pale and get brown spots. (Fergus Falls, Minn.)

A: Your maple has terminal chlorosis. This could be brought on by a number of factors: a rising water table, root decay, a high soil pH (alkaline soil) or flooding during a critical part of the growing season.

The tree may hang on for a year or two before it dies. I have seen many heroic attempts to save them at this point, but none have succeeded. I suggest making plans to convert it to firewood. Sorry!

Q: I have enclosed a small branch from my red maple tree that was a gift 10 years ago. For the last few years the leaves have started to turn yellow and drop off. I have tried fertilizer spikes and iron granules, but I don't think it is helping. Also, is the white cocoon a limb worm? (Breckenridge, Minn.)

A: The tree was a thoughtful gift, but an inappropriate selection. This species is not well adapted to our area. The white cocoon on the limb is a cottony cushion scale insect. They usually get established on trees and shrubs that are under stress. Which yours obviously is.

I have enclosed an extension publication, "A Guide to Deciduous Tree Knowledge" (F-436), which should help you make better future selections.

Q. Enclosed are two leaves from a beautiful, bright red tree I viewed on a recent trip to New York City and Washington D.C. The inner leaves were still green framing the deep red of the outer leaves.

No one seemed to know what kind of a tree it waslet alone whether it would be hardy here in Fergus Falls! Can you help me out? The bus driver said he thought it was a sugar maple.

If they are hardy here, and turn as brilliant as they were in DC, I would like to get one for my back yard. Any help you can give me would be appreciated. (Fergus Falls, Minn.)

A. Your leaf samples are from a red maple, Acer rubrum. The cultivars `Autumn Flame' and `Autumn Spire' would grow in your area, with latter being the better choice, as it came from the University of Minnesota research efforts. It is completely winter hardy, has a brilliant red fall color, and broad columnar form. It would get between 30 feet to 50 feet in height. Just make sure the soil is well-drained where you intend to plant.

Thanks for writing.

Q. We are faithful readers of your column in the Edmore Herald. I migrated from Edmore about 40 years ago because of a couple years of crop failure due to black stem rust on durum. We find your column very interesting, as we have a garden as well as trees and shrubs.

What we are wondering about are the seeds from a maple tree that we have had for 20 years now, purchased as a "Royal Red Maple." We have replanted seedlings from the tree and they start out with a red color, but later seem to turn green, so we dig them out again. Could they be from some other variety, or is the tree a hybrid? This year I have picked up some of the seeds, of which I will enclose a few. I suppose the seedlings we planted could have drifted in from elsewhere.

Thank you for your consideration. (New Brighton, Minn.)

A. I am always happy to hear from faithful readers like you and am glad to know that this cultivar of Norway Maple is doing well for you.

I wish it came true from seed, but alas, not so. It is a clone, propagated asexually, so the sexual part--the seeds--would not produce identical individuals.

Thanks anyway for the seed!

Q: I have been looking for a maple tree to plant in my yard. I wanted a royal red maple, but they seem to be hard to find. I’m told they don't grow very well around here but that they may grow OK in older established neighborhoods near the river. I don't live near the river, but I do live in an older neighborhood. I want a royal red maple because of its deep red leaves to add some season-long color. The nursery told me about a autumn blaze maple that gets blood red in the fall. If they do always turn that would be OK, I guess. What do you think would be my best choice of trees if I would like some color? (Fargo, N.D., e-mail)

A: The autumn blaze would definitely be the better choice, and yes, it will always turn that color red in the fall. The royal red is a cultivar of the Norway maple, and it simply does not do well in our part of the country--old neighborhood or not. You don't want something to simply survive but to look good and grow with some vigor. The autumn blaze will do that for you.

Q: Can you tell me why my red maple tree that I planted in the beginning of May is not doing very well? It was healthy when I planted it, but since then every new leaf that comes out turns black around the edges and then gets dry. It has had enough water and I have been spraying it with Triple-Action (insecticide-miticide-fungicide) since the middle of June. Nothing seems to help. Thank you. (Bemidji, Minn.)

A: The plant appears to be suffering from leaf scorch- - which is a poor description of what is actually going on. In your particular case, this is an abiotic (non-pathogenic) cause. Simply put, the roots lack the capability to supply sufficient water for that lost at critical times. Newly transplanted trees (within the last year) frequently manifest this problem. This ties in directly with the condition the root system is in. Perhaps too much was removed during the nursery digging; the salts (from fertilizer or otherwise) could be too high, the soil could be anaerobic from a rising water table, too much watering, or simply from compaction. Other problems could be a root disease, plastic mulch over the roots, too much mulch ("mulch volcanos"!) or an early infestation of feeding aphids. I suggest trying to give the tree as much reasonable good care as possible. Don’t over-water, do not fertilize, but attempt to keep the tree from undergoing any excessive stress. You might want to get a soil test taken and request to have the potassium (K) level checked. If it is low, then an application of that element as potassium sulfate may help. Other pointers might include vertical mulching- - vertically augur the soil out at several places around the tree, going down about 12 inches and backfilling with pea gravel- - and finally, spraying the tree with an anti-desiccant like Wilt-Pruf as the new foliage emerges next spring.

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