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Thursday - March 10, 2011

From: Austin, TX
Region: Southwest
Topic: Trees
Title: Roots in mulch around Live Oak in Austin
Answered by: Barbara Medford

QUESTION:

I have a 20 yr old Live Oak that has about 6-8 inches of mulch buildup around the base (I had landscaped around it). I went to break up the mulch to remove it from the base of the tree, but found it was packed with roots, that I will have to break up with an ax to clear the tree base. Will this harm the tree? Should I leave it as is, or is the buildup around the tree base a greater risk to the tree?

ANSWER:

First and foremost, we never recommend piling mulch, dirt or even fallen leaves up around the base of any tree. This can encourage fungi and provide harbor for insects. Mulch under a tree is not a bad idea because this helps protect the roots from heat and cold damage and can suppress weeds. Mulch ON the tree is not good. Get it off, and keep it off.

Do not, please, take an axe to this tree, This is a proven way to invite Oak Wilt into your Live Oak. Any damage to a tree is going to produce sap flowing, and the Nitidulid beetle, carrying the spores of Oak Wilt on his body, will come swarming in to drink that sap. Live Oaks are the most vulnerable trees to Oak Wilt, and this is the worse possible time of the year for them to be exposed. Oaks should be pruned only in the hottest and coldest times of the year, when the beetle is not active. See this website on the Texas Oak Wilt Information Partnership for more information.

Tree roots need oxygen. Putting such a thick layer of mulch over the root area probably forced the growth of roots trying to get to some air. For the time being, we would suggest you leave those exposed roots alone, and mulch no deeper than about 2 inches, with zero inches up against the trunk.

 

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