Questions on: Amur Maples
Ron Smith, Extension Horticulturist, NDSU Extension Service
Q: I planted a bunch of privit amur a few years ago. It was doing well, but this year it appears that most of the woody branches died during the winter. However, a lot more new shoots are coming up from the base. What causes this and how do I prevent it from happening again? Also, I am looking for a fast-growing privacy screen that I can plant over an area that contains part of my septic system leach bed. However, I know certain plants like to break pipes in search of water. Can you recommend anything for my needs? (Morgantown, W.Va.)
A: Amur river privet is the hardiest privet on the market and should be hardy enough for Morgantown. It used to be a common hedge plant in Buffalo, N.Y. What I slightly suspect is that you were sold California privet, which is less hardy than the amur river. As long as it is coming back this season, I wouldn't worry about it. Don't overfertilize the plants. If you do any fertilizing, don't go beyond the end of August so the woody stems have a chance to harden off before winter. You are making a common, but incorrect assumption about tree roots. They do not break pipes in search of water. If the pipes are leaking, then the roots will follow a path to the water source. That said, I still wouldn't recommend a weeping willow as a tree to plant in the area. If you don't need anything too tall, try amur or tatarian maple, pekin lilac, gray dogwood or possibly the Laurel willow, which is not at all like the common weeping willow.
Q: I have an amur maple. It has done well until recently, when its leaves started to turn a lighter green. Now I have several leaves with black or dark brown around the edges. Another amur maple a short distance away does not have these symptoms. Any ideas about the problem? Should I trim off the branches that show these symptoms? (e-mail reference)
A: Get some Miracle-Gro or Miracid applied to the foliage and around the dripline of the tree. This is often a symptom of a micronutrient deficiency, which usually is iron. If not corrected quickly, it could lead to the decline of the tree. The foliage will not change this season, but applying it now will get the elements into the soil and vascular system of the tree. If applied again next spring, just as the leaves are opening, you may be able to reverse the problem.
Q: We have a three-year-old amur maple that has been healthy. It has developed a 2-inch-long canker on the trunk 2 feet off the ground. Using a sterilized knife, I cut out the canker. The next day the area looked healthy, but had developed a bit of a blackened area over it. I cut this off and sprayed sulfur on it. The next day it again was covered in a dark, greenish black, but less than the day before. I watered the tree and it all came off. Is this oozing sap to heal the tree or is this the bacteria from the canker? Should I continue to cut out the black that appears or leave it be? Is there anything else I can do to help this tree? Otherwise, it is growing healthy leaves and the remainder of the trunk looks very healthy. (e-mail reference)
A: If you are cutting back to healthy tissue, there should be no strange flow of black, oozing sap. It is very unusual for a tree this young and of this species to develop a canker problem. Cut to where the bark is firmly attached to the trunk and let it go. If the tree is going to heal, it will do so on its own. Any spraying you might do at this point would do little to no good. Young and otherwise healthy trees such as this have the ability to compartmentalize wounds very quickly. The tree begins healing by sealing off the outer surface, then forming callus tissue, which gradually rolls over the wounded area.
Q: We live near Brookings, S.D. We bought the land in 2000 and have been planting new shelterbelts since then. We have done this before using trees from the Conservation Service and usually are good at it! Weíre having trouble growing amur maples in a couple of areas. We have discovered that area used to be old cattle or hog lots. The evergreens are doing well, as are the red twig dogwoods and the chokecherries. Is there too much of a particular nutrient in this ground for amur maples to thrive? If so, is there anything we can do or should we give up and replace them with another shrub? What would grow well in this soil? I read your column every week and have learned so much. Thank you! (Arlington, S.D.)
A: It is unusual that amur maples will not grow where other plants will. I donít know what to say, except to go with the ones that will make it. Generally, amur maples will grow almost anywhere, in some cases to the point of almost being a pest! Thanks for being a faithful reader of the column!
Q: What is the difference between clump amur maple and the tree form? I want to use the tree form, but Iím concerned that it may grow too tall. Is it like the clump form, but grows to about 20 feet? (e-mail reference)
A: Thatís it! They are beautiful small trees. I have one in my backyard and love the coloration and seed show.
Q: Can I prune my amur maples to make them into an even hedge? How far apart should I have planted to use them as a hedge or privacy fence? (Braham, Minn.)
A: They can be used as a hedge but that destroys the natural beauty of these plants. You could plant them as close together as you want to quickly have privacy and closure.
Q: Last year we planted two beautiful Amur maple trees. Now that the warranty has expired, they haven't flourished. My neighbor told me about a spray that he used in early spring and fall that worked for his trees in the same situation but couldn't remember the name. My trees are finally getting several leaves at the bottom but the rest remains bare. Any suggestions? They cost me a fortune! (E-mail reference)
A: I would go back to the nursery you purchased them from. Something has killed your trees and they should at least meet you halfway with replacements or advise you on what caused their rapid decline. I suspect they may have been planted too deep from what you describe. No spray in the world is going to bring dead tissue back to life.
Q: Are the enclosed leaves from two different trees? They are on the north and south sides of my yard. If so, what kind are they? Is there anything I should watch out for with these trees? (Osage, Minn.)
A: Both trees are Amur maples, Acer ginnala. What you are seeing is leaf dimorphism--variations within the species. Watch these trees for iron chlorosis. I suggest using Miracid to keep the microelements available.
Q: I have an Amur maple tree, about 10 years old. It looks healthy, but it does not turn red in the fall like pictures portray it. Do these trees take special fertilizers or soils? (Wahpeton, N.D.)
A: Your Amur maple was a seedling selection and not a cultivar. Consequently, you got the losing roll of the dice. Next time, you will want to select from the following cultivars for dependable red fall color: Embers, Flame, and Red Wing.
Q: Can you tell me what kind of bush the enclosed leaves and seeds are from? They are really beautiful in the fall, and we would like to plant some in our yard. I would also like information on Amur maple trees and Canadian red cherry trees. (Garrison, N.D.)
A: It's a small irony that you requested information on a tree you wanted identified, the Amur mapleAcer ginnala. I have one in my back yard by the patio and I love it!
Q: Can you identify the leaves enclosed from this tree (bush) for me? It turns beautiful red at the first frost. (New Delhi, India)
A: The tree is the beautiful Amur mapleAcer giunala. It ranges from hardiness zone 2 (southern Canada) to zone 8 (central TX, GA, AL), although it does better in the more northern zones.
Q. I stopped at our local office this morning and they gave me your pruning pamphlet for an answer to my question regarding pruning medium amur maples. It is still not clear how I should proceed to do them and I might add I have left them for a couple of years undone.
Would you have more information than the March 1992 publication?
Thanks kindly. (Aberdeen, S.D.)
A. The publication you refer to is to be used as a general guideline. It would be impossible to write an extension publication that could address all the possible particulars for the woody plant material in our region. That is where specialists like me come in.
Of all the maples, the amur maple (acer ginnala) requires very little to no pruning. Mid to late summer is the ideal time to prune. Remove only those branches that are dead, diseased or destroying the natural aesthetics of this multistemmed, small tree. Do not remove any of the trunks at ground level, unless completely dead. Prune instead, to retain the natural form, taking longer branches off with heavy-duty loppers or pruning saws. Do not over-prune. When in doubt, stop!
Since you say they have gone several years without any pruning, the temptation is to try and "catch up." It is better to do a little each year than a heavy pruning every few.
Finally, no tree-wound dressing is needed. Try and get to this ASAP, as the season is running out on us.
Q. Enclosed is a clipping of the diseased end and one that isn't. Is it a cut leaf maple? What do you advise to prevent further disease? It was planted 40 years ago. (Hope, N.D.)
A. Your sample is from what is known as the Amur Maple, Acer ginnala, which has "cut" leaves. A good tree.
Unfortunately, your tree appears to have the symptoms of a virus, TbRSV (tobacco ringspot virus), a disease often associated with trees in decline, which in the case of your maple, could be possible after 40 plus years.
I suggest pruning the affected branches out and fertilizing the tree with Miracle-Gro to help improve plant vigor. Perhaps you can slow or temporarily stop the spread of this disease on this beautiful tree.
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