Mulch a multi-purpose matter in the landscape

Tuesday, January 7, 2025

Media Contact: Trisha Gedon | Sr. Communications Specialist | 405-744-3625 | trisha.gedon@okstate.edu

Quality soil and adequate moisture are two must-haves for successful gardening. Mulch is another key factor that plays an important role, not only for aesthetics but also for plant health.

Gardeners put a lot of effort into their landscape, and adding mulch will help reap many benefits, said David Hillock, Oklahoma State University Extension consumer horticulturist.

“Mulching garden soil is one of the most valuable, cultural practices of gardening,” Hillock said. “Using organic mulch provides many benefits, including controlling weeds, reducing water evaporation, increasing water absorption and retention, regulating soil temperature, and decreasing water runoff and soil erosion.”

Mulch also contributes to more easily harvested crops, reduces fruit rot, prevents trunk damage from lawn equipment, provides a home for beneficial organisms like earthworms and makes it easier to maneuver in the garden when the soil is wet.

In addition, he said mulch helps prevent soil compaction caused by foot traffic in the garden. Soil compaction can have a detrimental effect on plant root growth because it inhibits access to air and water.

Hillock said there are two types of mulch — organic and inorganic. Organic mulches come from natural materials such as wood chips, cotton seed hulls, peat moss, compost, sawdust, ground corncobs, straw or leaves. They are typically low-cost, can deter insects and pests, and increase soil quality as they decompose. Inorganic mulches include shredded rubber, recycled glass or rocks.

“A lot of soil in Oklahoma has high mineral content but is low in organic matter. Using organic mulches in the home garden and incorporating them into the soil at the close of each gardening season is an opportunity to increase the organic matter content, improve the physical condition of the soil and add nutrients,” he said.

Generally, mulch is applied soon after the plants sprout from the ground in the spring. If the soil hasn’t warmed sufficiently, delay mulch application. Waiting to spread mulch is also recommended in a very wet spring when plant roots could develop in the mulch layer.

When applying mulch, the depth will vary depending on the type used. One of the primary objectives of mulch is to reduce the germination and growth of annual weeds and grasses. Another depth factor is the need to protect foliage, flowers and fruits from soil-borne disease organisms that could splash on the plants. Hillock said mulch can also prevent the development of fruit rots or leaf diseases. Don’t mound the mulch directly around the base of trees and shrubs because it can cause trunk rot.

Although not generally recommended, landscape fabric is an alternative to mulch and used mainly as a weed barrier. Water and air can penetrate the surface. However, the material becomes plugged up by soil particles and other debris over time, resulting in poor water and oxygen movement to plant roots. When this happens, plant roots creep up to the soil surface in search of water, oxygen and nutrients, which leads to plant stress. Most gardeners who opt for landscape fabric also use decorative mulch.

“With much of the gardening season coming to a close, start thinking about your spring gardening goals and how you can incorporate mulch into your plans for a more productive garden with hopefully fewer weeding chores,” Hillock said.

OSU Extension offers additional gardening information online.