Margaret Lauterbach

Mulching around plants remains vital. Here’s how to make sure you get it right.

A woman spreads mulch around a plant and flower garden in 2016.
A woman spreads mulch around a plant and flower garden in 2016. McClatchy file photo

Whether your garden interests lie with growing food or growing ornamentals, you should mulch around your plants. There are several good reasons for mulching, not the least of which is retaining moisture in the root zone of plants. Water is precious and costly, if you’re on the Suez system. Another reason is for weed suppression. If there’s no bare soil, weed seeds cannot germinate. Organic mulches will also feed as well as protect your soil. All mulches should be kept an inch or 2 away from the growing stalk or trunk of plants so they don’t develop crown rot.

Mulching generally will not smother and kill plants. Scrape weed leaves off with a hoe or similar scraper before applying a mulch. Annual weeds will die, deprived of their leaves. Perennial weeds may come up through mulch, but they’re easier to deal with than a mat of annual weeds. You can use organic matter for mulch, or nonorganic matter such as ground rubber, gravel or stones. Organic matter may be newspaper, cardboard, shredded paper, bark chips, soil aid, fallen leaves, rice hulls, ground corncobs or grass clippings. If you use grass clippings, make sure they’ve not been sprayed with a persistent herbicide to “kill” dandelions (2,4-D just hastens their maturity and seed-setting). Soil aid is lightly composted sawdust from lumber operations. Wet it down before it blows away, though.

One mulch that’s readily available and inexpensive is bark/wood chips from the folks responsible for city trees in the Boise Parks and Recreation community forestry division. Chips are $16 per cubic yard or $3 per garbage bag. They usually help load open-bed pickups or trailers, but call first (208-608-7700) to make sure their equipment is not needed elsewhere. They usually load from 7 to 10 a.m. on Wednesdays and noon to 3 p.m. on Fridays at Dorman and Orchard streets.

One word of caution: If you have a light-colored house or car that may be parked near a shade garden or other landscape feature on which you want to use chipped bark or branches, you may see results of artillery fungus. This is a fungus that grows on damp and shaded wood chips. The fungus fires its spores with sufficient velocity to travel several feet. Those spores are little black blobs that are nearly impossible to remove without damaging the original surface. They’ll outlast any glued item.

A huge benefit of using organic materials for mulch is that it feeds the microherd in your soil. Fungi, bacteria, other microscopic creatures, and earthworms, sowbugs, centipedes and millipedes, for instance, feed on organic mulch, altering it to a digestible state by those creatures. These microscopic creatures then feed your plants and protect them from disease. When you lay organic mulch, you may have to replenish it a time or two during the growing season to keep the ground covered.

There is another organic mulch commercially available, but I do not recommend its use: cocoa shell mulch. It smells like chocolate and is thus enticing to gardeners, but it’s also enticing to dogs and cats who want to eat it. There is enough theobromine in the mulch to kill dogs and cats within hours after eating it. Your pet or someone else’s should be protected.

Soil crawlers such as sowbugs (aka roly-polies, plant lice, roll-up bugs) start the decay process of mulch, but usually don’t feed on growing plants (strawberries touching the ground is one exception, though). Mulch may be consumed or pulled into the root zone of plants by visible or microscopic creatures such as earthworms, millipedes, sowbugs, and other beetles and worms. Earthworms till your soil, feed on organic matter, and leave their excrement (castings) improving the tilth and fertility of your soil. Centipedes are carnivorous, feeding on other soil-dwelling creatures, and millipedes (more legs, slower movement) eat decaying plant matter and sometimes other soil-dwelling creatures. All of the residue and excrement enriches our soil.

Nonorganic mulch only protects the soil without feeding it. It does retain moisture and bars weeds, but since nothing is consuming it, when you’re through growing in that area or want to grow something different, you’re faced with removing and disposing of that gravel, rocks, chopped rubber, etc.

Some gardeners, such as those raising hot chiles, want more heat around their plants, so use large heat-retaining stones near the plants. Such stones do help retain moisture, and since one would use fewer of them, they’re easier to clean out when necessary.

Send garden questions to or Gardening, The Statesman, P.O. Box 40, Boise, ID 83707.