How to Mulch Trees

Proper Mulching

The time to mulch a tree is right after you plant it. Before you mulch, get rid of any weeds. Start the mulch ring a few inches from the tree trunk and extend outward in a circle to at least the dripline, preferably 4 to 6 feet wide. Wider is better because the mulch will keep grass from competing with the tree for nutrients and water. The mulch layer should be 2 to 4 inches deep. When you get to the outer edge, taper out to the grass. Do not let the mulch touch the tree trunk. This could expose the trunk to disease, too much moisture, insects and other pests.

Every other spring, when the soil is warm, you will need to rake the existing mulch to get rid of clumps and hardened areas. Keep the old mulch, which is in the process of breaking down into the soil, in place. You may apply new mulch if needed as long as the depth does not exceed 2 to 4 inches.

A Properly Mulched Tree
Photo: International Society of Arboriculture

Improper (Volcano) Mulching

An Improperly Mulched Tree
A Tree Volcano
Photo: International Society of Arboriculture

Stay away from mulch volcanoes, where mulch is placed in a cone shape around the tree trunk. These volcanoes can extend far up the tree trunk to begin with, and the person who mulched it improperly the first time is likely to keep adding mulch higher and higher. Volcanoes can extend 12 inches up the truck with a width of 2 feet. It wastes money and hurts the tree.

Where the mulch volcano touches the tree bark, moisture can damage the tree by causing cracks in the bark. The cracks serve an entry points for fungus and insects. When you water the tree, it runs off the sides of the volcano instead of penetrating down to the roots. The volcano can keep oxygen from reaching the roots of the tree, suffocating them. As a result, roots can grow up into the mulch in search of what they need. Roots can rot if the volcano keeps the moisture in too long.

Benefits of Mulching

Mulching has many benefits, including the following:

Keeps weeds away from the tree

Keeps weed trimmers and other equipment away from the tree

Prevents soil erosion and runoff

Keeps the roots cooler in summer and warmer in winter

Postpones freezing of the soil

Adds nutrients to the soil (organic mulch only)

Increases aeration of the soil

Improves the soil structure

Keeps moisture in

Gives the yard a well-maintained appearance

For More Information

Learn why mulch is your best friend. For further information on tree mulching, visit the Virginia Cooperative Extension and the International Society of Arboriculture websites.