Mulching Trees the Right Way (and Avoiding Mulch Volcanoes)

A ring of mulch is one of the best things you can give a tree, as long as it goes on flat and stays off the trunk.

Why Mulch Helps

• It holds moisture in the soil through hot Virginia summers.
• It keeps soil temperatures steadier in heat and cold.
• It keeps grass from competing with tree roots for water.
• It keeps mowers and string trimmers away from the trunk. Thin-barked trees like red maple, beech and dogwood are easily wounded, and those wounds let in decay and borers.
• It breaks down into organic matter that improves the soil, the way leaf litter does in a forest.

How to Mulch

1. Clear the area. Remove grass and weeds in a ring around the tree.
2. Go wide. Make the ring at least 3 feet across for a young tree. Wider is better. Out to the edge of the canopy is ideal for a mature tree.
3. Keep it shallow. Spread 2 to 4 inches of mulch. Coarse fresh wood chips can go a little deeper because they settle.
4. Keep it off the trunk. Pull mulch back 3 to 6 inches from the bark so the root flare stays visible.
5. Keep it flat. The finished ring should look like a donut or a wide saucer, not a cone.

The Problem With Mulch Volcanoes

Mulch piled high against the trunk is one of the most common tree care mistakes in Virginia neighborhoods. It looks tidy, but it causes real harm:

• Bark kept constantly wet begins to rot, opening the tree to fungus and insects.
• Voles and other rodents tunnel in the mulch and chew the bark.
• Roots grow up into the mulch pile, then circle and girdle the trunk.
• A steep pile sheds rain away from the roots instead of letting it soak in.

If you have a volcano, rake the mulch back until you can see the trunk flaring out at the base. Then spread it out into a wide, flat ring.

What Mulch to Use

• Shredded hardwood or wood chips. Good all-around choices that break down slowly.
• Pine straw. Popular across Hampton Roads, light and easy to spread, and it won't wash away as easily on slopes.
• Shredded leaves. Free, and exactly what trees get in nature.
• Skip these around trees: landscape fabric, plastic sheeting, rubber mulch and rock piled against trunks. They trap heat, block air and water, or don't add anything to the soil.

Keeping It Up

Check mulch once a year, usually in spring. Rake up the old layer and add only enough to bring it back to 2 to 4 inches. Adding a fresh layer on top every year without raking is how volcanoes get built.