Asked June 14, 2013, 12:56 PM EDT

I got a sienna glen maple transfered last summer from a local tree farm. I noticed yesterday that there are some dead leaves falling. We have it planted with rock around it but not directly around the trunk. I was wondering what we can do. Should I remove the rock? Is there a certain type of fertilizer that I should try? Thanks in advance!

Clay County Minnesota trees and shrubs horticulture

3 Responses

First you need to know why you are seeing dead leaves. Are they being pruned by squirrels and you see them on the ground a few days later- dead (the leaves, not the squirrels), but the leaves are alive when pruned. Are the leaves yellow? Are they dried up and brown? Do they have dots on them? How does the tree look in general? How big was the tree when planted last year? Was it watered until the ground was frozen? or just until the frost and leaf drop? Do you have plastic or landscape fabric (porous) under the rocks?
We had a very hot and dry year last year, a winter will little/late snow and a long drawn out wet and cold spring. All of these can stress a tree. The tree may not need fertilizer unless the leaves are very small and pale in color and the soil is very sandy (and you used landscape fabric under the rocks--that is a good product to use under the rocks, not the plastic) The rocks should not be a problem. If you have plastic under the rocks it should be removed and replaced with landscape fabric. We have had lots of extra water this spring, that could stress a tree in a heavy clay soil. In this case the only thing you could do is remove the rocks and fabric and allow the soil to dry a bit. We have also had heavy winds and some hail storms, both of which can damage the connective tissues that hold the leaf stems to the tree and cause the connection to break and the leaves to fall/die. If you have had a very late frost there may have been some damage to leaves and those leaves have died and are falling. If the tree looks good generally, you have used landscape fabric under the rocks, the tree was well watered last year and planted at the correct depth then the tree should be fine.
This article talks about verticillium wilt, that can impact maple trees. But this does not sound like what you are seeing. I hope this helps with some of your questions. Thank you for asking the eXtension site your question.

Ok thank you. It sounds like we are doing what we should. We do have a lot of clay and one part of the tree has yellowish leaves. What is the best kind of fertilizer to use? Thanks for your help!

Any balanced fertilzer will work. You can use a granular fertilizer- even a lawn fertilizer without herbicide (broad leaf weed killer) in it. Depending upon how far out the rocks go, once the tree canopy reaches past the rocks you can top dress that area of lawn or garden with compost. It will work into the soil and feed the trees.
Normally you should not have to fertilize trees, occasionally fertilize shrubs, once a year fertilize perennials and if you grow annuals, they need fertilizing once a week or every 2-3 weeks depending upon the type of fertilizer you use. Trees need to send their roots 'out looking' for nutrition so it is good for them to be hungry to do that. Since they have been in the ground at least 1 year you can safely apply the granular (or if you want to water in something you can use miracle gro, fish emulsion or kelp) and not worry about damaging new roots. I hope this answers your question. Good luck with your trees.