Volcano mulching continues to be an epidemic in the landscape. It has me thinking, if we cannot get people to avoid mounding mulch up against their trees’ trunks, maybe we should do without mulch all together.
Gasp! I do love fresh mulch. I love the clean look of a fresh layer of pine fines and I love what it can do worked into clay soil. I understand the appeal of mulch. But let’s look at why we mulch around trees:
“We are protecting the tree and any above-surface roots from the mower and string trimmer.” That is great, but if the mulch is smothering the tree and inviting pests, disease and stress, then the protection is for naught.
“We want to protect the drip line of the tree.” Let’s address the old belief that tree’s roots only reach as far as its drip line. Not true! Quoting from Arborist News, "(1) Tree root systems extend out 2 to 3 times the drip line, (2) most roots are in the top foot (30.5 cm) of soil, (3) roots extend out about 1.5 times the height of the tree and (4) more than 60 percent of the absorbing root system is beyond the drip line."
“Adding several inches of mulch each year is good for the tree and smothers out weeds.” But as we just read, most of a tree’s roots are in the top foot of soil, so adding inches upon inches of mulch year after year only buries the roots, causing the tree stress.
What to do under a tree besides mulch it? Here are some ideas:
If you want a lawn, let it grow up to the tree. Keep your lawn tall to suppress weeds and reduce the need for watering and gently pull any unwanted lawn away from the base of the trunk.
Or, better yet, plant sedges (Carex). These grass-like plants are by and large more suited to the dry shade conditions that develop beneath trees than conventional turfgrasses are.
But why stop with grasses and sedges? There are plenty of other ground-covering options that offer a chance to play with color and texture, too. Sweet woodruff (Galium odoratum) is easy to grow and easy to pull from where it is not wanted, thanks to its shallow roots. Other perennial ground covers for dry shade include barrenwort (Epimedium), spotted geranium (Geranium maculatum), hellebores (Helleborus), Solomon's seal (Polygonatum), bearberry (Cornus canadensis), assorted native ferns and more. Ask at your favorite nursery for the best options for your area and its trees.
Planting and tending the ground beneath trees sounds like more work than simply dumping mulch there once a year. Possibly, yes. But I'd rather invest time and energy on an alternative to mulch than risk the health of a decades-old oak or maple.
