Question
I want to install landscape edging and mulch around existing trees. If I remove the sod will it damage the trees, or am I best to leave the sod then install the edges and place the mulch on top of the existing grass?

Answer
Jim:
If done properly and at the right age, adding mulch below your trees is a good way to improve the conditions for the tree and improve the appearance of your yard. To start with, I do not recommend plastic edging. I recommend either no edging, which requires regular maintenance with a weed whip or edger, or I recommend steel edging. Plastic typically gets hit by lawn mowers and quickly becomes something you wont like the look of. Second, I would be sure you provide enough room under the tree to make a difference. Adding a tiny ring of a few feet around a large older tree will do nothing for the tree and be hard to accomplish due to the roots, not to mention harmful to the tree. Keep in mind about 90% of a tress roots are in the top 12" of soil. So any excavation you make around the an older tree to install an edger can be detrimental to the health of the tree. On an older tree its best not to install any edger at all and just maintain the edge above grade with a weed whip. If its a young or new tree, installing an edger can be done without much concern for roots. The mulch ring should grow in size each year with the tree. A good rule of thumb is a minimum diameter of about 36" for a small tree and then after that tree gets to be about 3" in caliper add about a 6" (in radial length) to the ring for each inch in caliper. So a 4" tree will have at least an 24" radius mulched area and a 8" tree would have 8 foot diameter mulch ring. However, once a tree reaches maturity and the crown width stops increasing you can stop increasing the ring at around 50% of the width of the canopy or crown. So a 30" tree with a canopy that is 40 feet across only needs a mulch circle of about 20 feet.

The mulch ring should never get too deep either. Maintain about 3-4" of good mulch and do not pile it up too high on the trunk.

Best of luck.
Sean J Murphy, LA
www.seanjmurphy.com