Ask the Master Gardeners: April 2011
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March 29, 2011 | 1654 views | Post a comment
Q: Tree roots from my front yard tree are sticking up out of my lawn. Can I cover them with soil, or will that kill the tree (or the grass)?
A: According to Doug Welsh on the Aggie Horticulture website, when soil or any type of fill is placed over the existing root system, it causes a reduction in the oxygen supply to the tree roots and slows down the rate of gas exchange between the roots and the air in the soil pore space and can kill the tree over time. This, of course, all depends on the type of tree, the depth and type of fill, the drainage, and the vigor of the tree. It won’t hurt at all to put a half-inch layer of compost around the tree.
Another question about tree roots on top of the ground was about the feasibility of removing them. In Aggie-Horticulture, there were a number of answers about different types of trees, but basically they said the same thing. You should not remove the roots, or if you do be very careful. One answer was that this is normal for some varieties of trees and root removal could damage the tree. Over a period of time minor roots could be removed a few at a time but not major ones.
Another answer said that it was unusual for roots of a live oak to come to the surface, but they could be removed one a year. And again, I’m assuming that means minor roots.
Removal of red bud tree roots is not recommended because the tree is prone to borers.
Removal of Arizona ash tree roots that are lying on top of the ground can be done, but again only one root a year.
Now, after all this, what can you do with those roots that stick up where your lawn mower can injure them? I just don’t know. The only thing I can think of is to enlarge the width of the mulch layer around the tree. My mulch layer comes out to the edge of the tree umbrella.
Q: Will cypress mulch work as well as hardwood type mulch?
A: Bark chips are long lasting and break down slowly. Cypress breaks down more slowly than pine bark, but it does break down. When mulch is shredded, it breaks down faster and helps maintain uniform soil temperatures. Cypress does not seem to float away when (and if) it rains, and, of course, it is cheaper. My favorite mulch is cedar because of the smell. I like putting it on the beds by my front door so that every time I open the door, I smell fresh cedar. My theory which is not really research based is that the smell helps deter bugs.
Clara Mae Marcotte is a Texas Master Gardener with the Texas AgriLife Extension
If you have a question to be answered, call the Master Gardeners at 830-379-1972 or leave a message to be answered. The website is guadalupecountymastergardeners.org. The Master Gardener research library is open Mondays from 8:30 to noon, on the second floor of the Texas AgriLife Extension building, 210 East Live Oak in Seguin.