Chlorosis in a red maple - Ask Extension
Hello,
6 years ago we planted two bare root red maples - one in our front lawn and one in a mulched garden bed near the edge of the woods behind ou...
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Chlorosis in a red maple #766230
Asked August 07, 2021, 2:55 PM EDT
Hello,
6 years ago we planted two bare root red maples - one in our front lawn and one in a mulched garden bed near the edge of the woods behind our house. We were new to planting trees then. Both trees have struggled with chlorosis for at least several years. We've treated them with Peak Iron with WolfTrax a few times over the past year, but it hasn't made much difference. The tree in the front lawn is quite a bit worse than the tree in the mulched garden in back, though both trees are suffering. This year the leaves at the top and on the sides have brown blotches between the veins. The drought certainly hasn't helped.
An arborist friend feels we should leave the lawn in place around the tree in the front lawn, feed it iron, tolerate the yellow leaves, and wait for its roots to expand far enough where it can get the nutrients it needs. She says it will outgrow the chlorosis. After reading several articles this weekend, most importantly the U of M's article, I cut out the lawn around the tree to the drip line, put down bark mulch, and bought aluminum sulfate. I plan to shop for iron chelate spikes. Then I remembered that we had done a soil test 5 years ago. The test at that time revealed that the pH level was 7.6, which I now know is too high for a red maple.
My questions for you are, will the trees every outgrow the chlorosis? am I fighting a losing battle? Should I replace the red maples with trees that are better suited to our soil or treat them with the aluminum sulfate and iron chelate?
I'm so grateful for this service.
Thank you!!!
Kari Baumbach
Dakota County Minnesota
Expert Response
Hello Kari, happy to help.
There could be a few different reasons why a tree has chlorotic leaves, the pH is not conducive to allow the tree's roots to take up the iron that's present in the soil (no matter how much iron is present), no iron in the soil, or other physical impedances that prevent the tree from taking up nutrients.
I'm guessing there's plenty of iron available so I don't recommend adding any more to either tree. Most Minnesota soils in the metro area are alkaline and we have lots of maples doing just fine even though they would like a little lower pH. Lowering the pH can be done with elemental sulfur or aluminum sulfate. I tend to stay away from aluminum sulfate because it can build up in the soil making it less habitable for lots of other plants. I recommend a soil test to determine what your soil really needs, Even though you had one done, things can change in five years. But first, check out these other possibilities.
Do you see a root flare at the base of your trees -a widening of the trunk where the main roots take off into the soil? If you don't, I suggest reading through the PDF provided in this link that talks about stem girdling.
If your trees have nicely exposed root flares, then this next possibility may be the case. It's a problem that occurs more often with potted trees. Grab your tree's trunk and tilt it in one direction and then in another direction. If that results in the soil breaking into a circle that appears to be about the circumference of a pot, the roots have not expanded properly and may be growing in a circle. That situation makes it difficult to get all the nutrients they need. The trees' roots should be gripping the ground well if they have expanded. It can happen if your soil in the planting area was seriously compacted. Sometimes roots can't expand into very compacted soil. I'm not sure if there's much you can do about that now given how terribly chlorotic they are. Let me know if you think this is the case and I'll take a stab at what you can do.
If you don't think your trees are affected by either of these two physical problems, then I think getting a soil test would be best so that you can supply what they really need. Be sure to ask the soil test people for the correct pH needed for your maple trees.
Good-luck!
There could be a few different reasons why a tree has chlorotic leaves, the pH is not conducive to allow the tree's roots to take up the iron that's present in the soil (no matter how much iron is present), no iron in the soil, or other physical impedances that prevent the tree from taking up nutrients.
I'm guessing there's plenty of iron available so I don't recommend adding any more to either tree. Most Minnesota soils in the metro area are alkaline and we have lots of maples doing just fine even though they would like a little lower pH. Lowering the pH can be done with elemental sulfur or aluminum sulfate. I tend to stay away from aluminum sulfate because it can build up in the soil making it less habitable for lots of other plants. I recommend a soil test to determine what your soil really needs, Even though you had one done, things can change in five years. But first, check out these other possibilities.
Do you see a root flare at the base of your trees -a widening of the trunk where the main roots take off into the soil? If you don't, I suggest reading through the PDF provided in this link that talks about stem girdling.
If your trees have nicely exposed root flares, then this next possibility may be the case. It's a problem that occurs more often with potted trees. Grab your tree's trunk and tilt it in one direction and then in another direction. If that results in the soil breaking into a circle that appears to be about the circumference of a pot, the roots have not expanded properly and may be growing in a circle. That situation makes it difficult to get all the nutrients they need. The trees' roots should be gripping the ground well if they have expanded. It can happen if your soil in the planting area was seriously compacted. Sometimes roots can't expand into very compacted soil. I'm not sure if there's much you can do about that now given how terribly chlorotic they are. Let me know if you think this is the case and I'll take a stab at what you can do.
If you don't think your trees are affected by either of these two physical problems, then I think getting a soil test would be best so that you can supply what they really need. Be sure to ask the soil test people for the correct pH needed for your maple trees.
Good-luck!
Thank you so much for the quick response. I’m going to have the soil tested and will get back with you once I have the results.
Again, thank you!
Kari
From: Ask Extension <<personal data hidden>>
Sent: Saturday, August 7, 2021 5:16 PM
To: Kari Baumbach <<personal data hidden>>
Subject: Re: Chlorosis in a red maple (#0036161)
