Proper Mulching Techniques

Mulching around your trees provides a good way to conserve moisture for your tree and keep plants healthy. Trees lose moisture from evaporation, mulching can conserve between 10 to 25 percent. They also help keep the soil well aerated by reducing soil compaction that results when raindrops hit the soil. Having the soil aerated in turn then reduces runoff and erosion. Mulch also helps keep the soil healthy, preventing possible fungi from causing soil-borne diseases.

Because trees sustain a lot of damage from lawn mowing and weed trimmers, adding mulch around the base of your trees can help reduce this damage. Professionals suggest a 2- to 4-inch layer. This will also help prevent most weeds from growing.

When applying your mulch, try and cover as much of the root zone as possible. The mulched area should extend at least 3 to 6 feet out from the base of the plant. Some suggest not putting the mulch right up against the base of the tree, leaving 1 to 2 inches - this can help prevent bark decay.

As far as how much mulch depth to build around your tree, this will depend on the type of soil surrounding it. Sandy soils dry out quickly and often benefit from a slightly deeper mulch layer (3 to 4 inches). A site that stays moist may not benefit from mulching at all.

You can apply your mulch any time of the year, but the most ideal is in late spring after the soil has warmed. Early spring application will delay soil warming and possibly plant growth. You do not have to remove the mulch when you fertilize, just apply the fertilizer over the mulch and the nutrients will move with water to the roots below.

In regards to what you can use for mulch, there are many materials out there - each with their advantages and disadvantages. Organic materials used for mulch should be weed-free. Some of the best organic materials include pine bark nuggets, pine straw, and compost. Pine straw looks nice and will remain in place better than most other materials but Pine bark lasts longer and can be washed with a heavy rain. Bark used as mulch should contain less than 10 percent wood fiber.

Other organic materials that are sometimes used as mulch include wheat straw, shredded newspaper, peanut hulls, wood chips, sawdust, and partially decomposed leaves. Any fresh, light-colored, unweathered organic mulch will tie up nitrogen during the early stages of decomposition.

Non-shredded leaves and grass clippings can form a thick mat that makes water penetration nearly impossible. If sawdust is used it should be well aged, otherwise it will be difficult for water to move into the soil. Uncomposted sawdust is low in nitrogen and will rob nitrogen from the soil as it decomposes.


With inorganic mulches, which include various types of stone, lava rock, pulverized rubber, geotextile fabrics, and other materials - they do not decompose and do not need to be replenished often. On the other hand, they do not improve soil structure, add organic materials, or provide nutrients. For these reasons, most horticulturists and arborists prefer organic mulches.

Mulching has many benefits to keeping your tree healthy and strong. If you have questions about the types of mulch to apply, ask your local arborist or even gardening center.

Andrew Johnson is the owner of Central Texas Tree Care, a leading tree service provider in Central Texas (Travis County and surrounding areas) offering services such as pruning and removals, cabling and bracing as well as arborist reports, diagnostics, pest management, fertilization and Austin tree service trusts. For more information please visit http://www.centraltexastreecare.com.