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PAL Questions: 1 - Garden Tools:
We planted a clump of vine maple last fall and because we were in a hurry (landscaping a new home), we just put in without amending the soil. It is dealing with extremely sandy soil, though we did give it fertile mulch, and gets full sun all day long. It looks okay, but the leaves have been very red all summer, basically what I would expect it to look like in the fall. We've been watering a lot to make up for the sand. What's the story on vine maples? We had a lot of them at our old house, but they were mostly under fir canopies or at least were not in full sun. Any tips on helping this one out?
I wonder if the leaves on your Acer circinatum are evenly red, and if they look scorched at all. Leaf scorch is a problem for maples in conditions of stress. See this information from the HortSense database of Washington State University. Excerpt:
"Leaf scorch on maple has many possible causes. Plants that are under stress, such as drought or heat stress, may not provide sufficient water to the leaf margins, causing the edges of the leaves to turn brown and dry. In some cases, scorch may spread to areas between veins or entire twigs may die back. Trees placed near heat-reflecting surfaces, such as buildings or pavement, often suffer from heat stress. Excessive salts from overuse of chemical fertilizers may cause leaf scorch. Scorch may also be a symptom of damage to the roots or stem."
If the leaves are not scorched in appearance, it is possible their early coloring is the result of some other type of stress, or perhaps the leaf coloration has to do with their being in full sun, in an exposed site. You may find this information from University of British Columbia Botanical Gardens interesting: "The formation of red pigments in the autumn provides protection, preventing the too-rapid breakdown of chlorophyll which could occur in exposed (read: excess light) areas. As you can clearly see in the leaf in the upper right, the bottom-right corner has the pattern of the leaf above. Where the leaf above shaded this leaf, no red pigments were produced. Where the leaf was exposed, bright red anthocyanins were formed. To take this to a broader perspective, vine maple trees in shaded forests and under low light conditions have little need to produce red pigments, as the breakdown of chlorophyll can occur at a modest pace. However, vine maples in exposed sites turn flame orange and red, so that the pigments produced will slow the rate of chlorophyll breakdown."
An article (no longer available online) from Minnesota Department of Natural Resources discusses premature fall color in maples. Excerpt:
"Each August brings a few trees that begin the fall color frenzy ahead of
schedule. In addition to signaling the change of seasons, these trees are
sending a clear signal that they are suffering from some form of stress.
Stress can have a wide variety of causes, be mild or severe, or, benign
or fatal. In any case, professional tree 'care givers' should be aware
that the trees are talking to you. Are you listening?
"Maples are probably the group of trees that most commonly exhibit premature fall color. Sensitive to changes in their environment, maples commonly show early color in years when summer rains are heavier than normal and raise soil moisture to or above field capacity during the period from mid to late summer. The maples that show this characteristic the best are the several species of soft maples (silver and red) that commonly inhabit the shrubby areas around wetlands. These trees commonly begin to show deep, rich purples as early as the first week in August. Maples in communities also commonly display early color due to stress mechanisms more common to the urban environment. Sugar maple, in particular, shows early color due to the stress induced by infection from Verticillium wilt. This disease may occur in nursery grown stock in commercial trade. It is difficult to detect because it is soil-borne, difficult to culture, and commonly not tested-for in the nursery. In addition, Verticillium wilt is a relatively weak pathogen that does not do well on young, vigorous nursery stock. Trees can be infected for many years without showing external symptoms of the disease. When they do begin to show symptoms, one of the first is premature fall color followed in succeeding years by a progressive, if not slow, crown decline and dieback."
Maples in communities that are planted 'just-a-little' too deep often show premature fall color. Again this is more pronounced in years with wet summers. The likely mode-of-action is decreased soil oxygen content. Planting too deep 'smothers' roots reducing oxygen in the root zone. So does over watering whether natural or artificial. The bottom line is stress-induced premature fall color. Remember that stress is (1) caused by many factors, (2) cumulative, and (3) potentially fatal if left untreated.
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January 13 2017 10:35:53