Plant Clinic

Important to keep mulch away from trunks

Q. I heard that mulch shouldn’t touch tree trunks. Can you tell me why?

K.G., West Palm Beach

First, it is important to understand the difference between organic and inorganic mulch. Organic mulch refers to organic matter such as bark, wood chips, leaves, straw, etc. Inorganic mulch is made of stones, glass, ground tires and other materials.

One of the reasons people use organic mulch is to conserve soil moisture. Although this is beneficial for plant roots, it can lead to various trunk diseases if the mulch is allowed to pile up around tree trunks, a.k.a. volcano mulch. As a general rule, keep mulch at least 2 inches away from the base of plants. This is less of a problem with inorganic mulch, but some of these materials can damage tree trunks in other ways.

Spread the mulch so it covers as much of the plant’s root zone as possible. This may mean that the mulch goes beyond the drip zone (the edge of the leaf canopy). Mulch should be kept 3-4 inches deep if you are using a coarse-type one such as pine bark. This means you need to check the level of the mulch every few months and reapply if needed.

To learn more about mulches, visit this website:

Adrian Hunsberger is an entomologist/horticulturist with the UF/IFAS Miami-Dade Extension office. Write to Plant Clinic, 18710 SW 288th St., Homestead, FL 33030; e-mail

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