<font color=red>QUICK TIPS</font> Much Too Much Mulch

Consulting arborist Dave Leonard erupts when he spots what he calls a "mulch volcano" around the base of a tree. With a wry sense of humor, he adds, "It's mulch madness."

The recent warm weather has many homeowners and lawn-care and landscape services shifting into high gear. They are raking leaves, weeding flower beds, spiffing up yards and laying down the annual layer of mulch.

Sure, the mulch looks very tidy, but is it good idea to pile a mound of mulch around the base of trees?

Leonard, who has a degree in forestry from the University of Kentucky and is president of Dave Leonard Consulting Arborist, says that piling up deep cones of mulch year after year can hurt a tree's health in several ways.

Some trees, especially red maples and other bottomland species, send roots into the mulch, creating a tangle of side roots that weaken the tree's support system. They can girdle the trunk in a stranglehold, causing premature decline by decreasing vascular flow.

Bill Fountain, extension professor of floriculture at UK's College of Agriculture, says putting mulch next to the trunk might cause fungal diseases and provide habitat for harmful insects and for mice and voles, which hibernate under deep mulch, then wake in February and gnaw the tree's bark for food.

He also warns against using anaerobic "steaming mulch," which is warm, smells bad and hasn't completely composted. It also gives off compounds that are toxic to plants and tree roots. As the mulch decomposes, fungi can form a water-resistant barrier on the surface, blocking the flow of water to the roots.

When used properly, mulch provides great benefits. It can be any material that is placed on the ground to help prevent weeds from growing in competition with the tree, and to help the soil retain moisture.

Mulch decomposition varies. Wood-chip mulch decomposes at the rate of about an inch a year, Leonard said. Cypress bark takes much longer. Composted leaves break down quickly.

Limiting mulch depth to two inches over slow-draining heavy clay soil or three inches over better soils, and breaking up old mulch so that water and air can penetrate easily, is optimal. The mulch should taper off near the trunk, so that the root flare is visible. If your tree looks like a utility pole coming out of the ground, it is covered too deeply.

Fountain suggests mimicking the natural woodland ecosystem, in which leaves and twigs drop evenly under the tree rather than pile against the trunk. He prefers chunky pine bark. As the mulch decomposes, it enriches the soil with organic nutrients, more closely simulating a natural ecosystem.

Other tree-care practices to avoid are staking and topping. Staking, or fastening supports next to newly planted trees, should be rare. Letting trees move slightly can stimulate root growth and trunk taper. Exceptions include places where mowers or pets can damage a tree, or extremely windy locations.

Leonard suggests using soft, flat polypropylene webbing, available in olive green or white. If you do stake a tree, remove the material after a year so that it doesn't hamper growth.

Topping, or pruning the top of a tree without regard to branching locations, creates large wounds that can't heal. Decay can set in and kill the tree. Many small, weak shoots called water sprouts pop up, ruining its structural stability and form. Removing the upper leaves, where photosynthesis occurs, reduces the plant's ability to make and store food.

Leonard and Fountain are associated with the International Society for Arboriculture, an organization dedicated to training and certification of professional arborists. The ISA Web site, www.treesaregood.org, is filled with tree-care information.