Garden and plant people all sing the praises of mulch. Mulch is organic matter that is usually partially decomposed or undecomposed. Compost is more fully decomposed organic matter, but it is sometimes used as a mulch.

You probably just need a bucket full for the average size tree basin. The mulch goes on top of the soil, about 3" deep. It’s not good to put undecomposed matter underground, as it will decompose without oxygen and give off sulfur. Don’t pile the mulch around the trunk, as this can cause trunk rot and tree death. Leave a space around the trunk a few inches in all directions.

The benefits of mulch are:

Holds moisture in the soil longer. A big benefit in our windy climate!

Suppresses weeds

Raises your tree basin to sidewalk level. When we cut the concrete, there is often a gap between the sidewalk level and the soil level. We plant the tree at sidewalk height to avoid it sinking too deeply. Depending on the size of the gap, you may need to add a bucket or two of native soil and then add the mulch.

Over time, improves the soil. The mulch breaks down into organic matter over time, which benefits all soil types. Just keep refreshing the mulch layer periodically.

Looks nice. Mulch as a top dressing is much better than brick, stone, or grating. Those other materials add nothing to the soil and can wound the tree if not adjusted. For heavy clay soils, they can actually compact the soil, causing roots to grow under the sidewalk rather than in the soil.

The most used materials for mulch in this area include wood chips, shredded bark or compost. Avoid sawdust and pine needles as they take too long to decompose and can actually rob nitrogen from the soil.

Note: For new trees in sandy soils, it helps to add a little organic nitrogen fertilizer just before mulching. Sandy soil is already low on nitrogen and mulch may temporarily lower nitrogen levels as it decomposes. This is not generally a concern for mature trees and plants.

Where to get mulch free or nearly free:

St Mary's Urban Youth Farm, 600 block Alemany just past Ellsworth
Naomi Goodwin, Garden Coordinator, slugsf@hotmail.com

Your own yard. Grass clippings, chopped leaves and branches make great mulches. Go in with your neighbors on a small chipper and share a mulch pile! When mulching, apply clippings in thin layers and allow to dry fully before applying another.

Bayview Green Waste: 1300 Carroll Avenue, off 3rd Street. Open to the public on Saturday from 7:30-noon. For weekday times, call 822-7686.

Feline Pine Cat Litter is an all natural cat litter that can be spread as mulch after it has been used. For more info see http://www.felinepine.com/felinepine/