Proper Use of Bark Mulch: Gardener's Supply

Mulch has all sorts of wonderful benefits for your landscape. But if it’s too close, too thick or too coarse, it can also cause problems! Here are three rules for proper mulching etiquette.

Not Too Close. Mulch volcanoes, like the image at right, are not only an eyesore. They also endanger a tree’s health. When mulch is mounded up around a tree’s trunk, it keeps the tree’s bark consistently moist. These are ideal conditions for a host of insect and disease problems. The warm, humid environment inside a mulch volcano is also a good growing environment for tree roots, which can girdle and eventually kill the tree.

Proper mulching etiquette requires that mulch be applied evenly around the base of the tree or shrub. It should lie flat, and always be pulled back several inches away from the tree’s base.

Not Too Thick. Applying mulch around the base of your trees or shrubs is a good way to suppress weeds and help retain soil moisture. But if the mulch is applied too thickly, the mulch itself will absorb rainwater and overhead irrigation, and prevent that water from reaching the tree’s roots. An overly thick layer of mulch can be an inviting environment for insects and even small rodents that can nibble on the tree’s bark.

Measuring from the soil surface, your mulch should be no more than 3-5 inches thick. Before applying a fresh layer in the spring, remove some or all of the mulch from the previous year and add it to your compost pile.

Not Too Coarse. Coarsely textured mulch (with individual pieces that are 1 inch or more in diameter) will not pack as tightly as finely textured mulch. Because wind-blown seeds – and light – can get between the larger pieces, coarsely textured mulch tends to be less effective at suppressing weeds. Small plants can also look dwarfed when they’re surrounded by big chunks of bark or 2-inch pieces of stone.

Mulching materials vary by region (bark chips and shredded bark mulch in the Northeast, pine needle and stone mulch in the South, compost and straw in the West). Use whatever mulch is most available in your area, but also consider matching the texture of the mulch to the size and type of plants you are mulching around.

Mulching Tip from a Reader:

"Having moved into a new home and bare landscape last year, among the items on the 'to-do' list was our landscaping, which required much mulch, so we ordered a full dump truck of dark mulch. It was dumped in four large piles that almost took your breath away when you thought about how to move it all over the lot.

"The only items at hand were a couple of plastic sleds. We would ease the side of the sled up to the mound and pull the mulch into the sled and the grandchildren ran to each area to spread the mulch – a regular production line!"

– John & Ann Barton, Soddy Daisy, Tenn.