By Eric Barrett
OSU Ext. educator
I know it’s tempting. The trees in your yard provide great shade, so why not plant a shade garden under them? The neighbors have a beautiful flower bed under their trees, so why can’t I have one? Here are some reasons to think twice about this practice and some tips to use the space wisely.
Keep mulch at 2-4 inches, at most, around tree trunks. Trees should have a natural flare, where the trunk tapers out. Burying this trunk causes stem-girdling roots.
Building up the soil around a tree causes the same problem. In the cases of smaller trees, the tree can be killed in 10-15 years by these roots. In the case of many maples, roots will form in this new soil, taking up a significant amount of water and nutrients.
Shallow roots are common on many evergreen trees and other species. Most tree roots are near the surface — 6-24 inches below the ground. These also rob flowers of water and nutrients.
To create a successful bed, plant (or move) the hostas, ferns and other plants a few feet away from the tree where they will get afternoon shade, but not compete with the tree.