Maple colors reflect extreme environmental changes
Q: We had several autumn blaze maples planted on our property during the spring of last year.
Beginning in mid-June of this year, one of the trees has progressively started to turn red. Based on the advice of the nursery, I've fertilized and watered the trees. The other autumn blaze trees also are showing some red coloration. However, the leaves still are predominantly light green, but small in size. I have clay soil and routinely windy conditions. We did have unusually heavy rains in June.
A: Maples probably are the group of trees that most commonly exhibit premature fall color because they are sensitive to changes in their environment. When weather extremes occur, maples will show early color. In all likelihood, this is what is ailing your trees. Anaerobic conditions develop when the soil is at saturation or field capacity, which stresses the trees. With clay soil, the problem is compounded even further.
Essentially, nutrients are unable to be taken up sufficiently when oxygen is lacking in the root zone. Although not likely, the problem could be from some vascular disease such as verticillium wilt. This is a weak pathogen and is almost never found affecting young, vigorous trees in this manner. If the trees were 25 or more years old, then this would be something to seriously consider.
Premature fall color and yellowed leaves can come from the trees being planted too deeply, especially in clay soil. I hope this is not the case because the nursery planted the trees. All I can tell you to do is wait this out. Check the depth of the trees to be sure the crown (where the stem becomes root) is level with the surrounding soil. Do not water excessively and don't push fertilization. Allow the soil to dry between waterings.
Check the moisture level by sticking your hand into the soil surrounding the root ball. When conditions return to something more normal next year, the trees should perform as you expect them to.
Q: We have a lovely, mature Japanese lilac in our backyard. Much to our dismay, limbs have started to die. We cut the dead limbs out, but more keep dying. The tree was in our yard when we moved here in 1988. Do you have any suggestions for saving the tree?
A: You need to examine the tree closely to try to discover what could be killing the branches. This could be the ash-lilac borer doing the dirty work. Other possibilities are a change in the water table on your property or a nectria canker developing on the stems. If it is insect- or disease-caused, there should be some evidence.
Q: I put hardwood mulch on top of black polyethylene sheeting by the side of my house. It has developed artillery fungus, which is making spots on my house. What can I do about this? Would replacing the polyethylene sheeting with a permeable fabric and red pine needles be a better choice?
A: You named it! Doing this also would be better for the health of your landscape plants because they will get more air in the root zone.
Q: I have a question for you about some arborvitae I planted. There are a couple of plants with bent or curved tops. I think they were that way when I purchased them. I planted the arborvitae about three weeks ago. Will they straighten by themselves or should I use stakes?
A: Don't worry because the arborvitae eventually will straighten up by spring of next year.
To contact Ron Smith for answers to your questions, write to Ron Smith, NDSU Department of Plant Sciences, Dept. 7670, Box 6050, Fargo, ND 58108-6050 or e-mail ronald.smith @ndsu.edu.