Cooperative Extension Service 
Institute of Food and Agricultural Sciences
Hendry County Extension, P.O. Box 68, LaBelle, Florida 33975-0068  Phone (863) 674-4092

Hendry County Horticulture News

Mulching Controls Weeds

Weeding must be one of the most universally disliked garden chores.  Tedious, back breaking, hot, itchy, time consuming, etc. are all adjectives that come immediately to mind when contemplating the chore of pulling weeds. The judicious use of mulches can greatly reduce the toil involved with weeding, while providing a number of other beneficial effects in the garden.

Mulches suppress weeds when the mulch material itself is weed-free and applied deeply enough to prevent weed germination or to smother existing small weeds.  The organic materials used as mulches can improve soil structure and tilth.  Improved tilth allows those weeds that do manage to grow to be easily pulled up roots and all.  As mulch decays, the material becomes topsoil. Decaying mulch may also add nutrients to the soil.  One caution though, as certain woody, high carbon mulches breakdown, the decomposing organisms may use available soil nitrogen robbing plants of this nutrient and require supplemental nitrogen fertilizer application.

In addition to weed control and labor savings, mulching benefits soil and plants in other ways. One of the greatest advantages of mulching is water conservation.  Mulches help prevent loss of water from the soil by evaporation. Moisture moves by capillary action to the surface and can evaporate if the soil is not covered by a mulch.  Mulching prevents crusting of the soil surface, improving the absorption and percolation of water into the soil and, at the same time, reducing erosion.

A more uniform soil temperature can be maintained by mulching. The mulch acts as an insulator keeping the soil cool under intense sunlight and warm during cold weather. Mulched plants will produce roots in the mulch that surrounds them. These roots are produced in addition to the roots that a plant produces in the soil. As a result, mulched plants have more roots than unmulched plants.

Mulches also add to the beauty of the landscape by providing a cover of uniform color and    interesting texture to the surface. Common mulch materials include leaves, pine needles, compost, bark, wood chips, sawdust, and bagasse (sugar cane by-product). Peat should not be used since once dry it is very difficult to wet and may restrict water movement into the soil. Inorganic materials such as glass wool, gravel, and crushed stone can also be used. Avoid using plastic mulches around landscape plants. They are undesirable barriers for water and gas exchange. A woven plastic fabric or other types of porous ground cloths can be used to help stabilize the soil, reduce weed penetration, and conserve moisture.  Fabrics should be covered with a mulch to prevent degradation of the material by sunlight and to increase the landscape's aesthetic quality.

Mulch can be applied around established plants at any time. Newly-set plants should be mulched
after they are planted and thoroughly watered. Because of the abundance of leaves and pine needles, fall is an excellent time to collect leaves and other yard trash for mulching plants.

Organic mulches will gradually decompose and need replenishing to function effectively as a mulch.  Shallow plant roots that grow up and into moist mulch will die if the mulch is allowed to decay or wash away. How often mulch needs to be replenished will depend on the mulching material. Grass clippings and leaves decompose very rapidly and need to be replenished frequently. Other organic mulches such as cypress mulch, pine bark and wood chips break down very slowly and need only be replenished every year or two. Once plants in a ground cover or shrub bed have formed a solid mass by touching one another, the mulching requirement is reduced. The plants create their own mulch by dropping leaves, flowers and fruit. Leaves from surrounding trees also may fall in the beds and provide additional "free mulch." Most organic mulches will change from their original colors to a weathered grey color with age. There are several ways of restoring color to mulches. One approach is to apply a thin (1 inch or less) layer of fresh mulch to the surface of the existing mulch. This approach is labor intensive, and can result in an excessively thick mulch layer. Another approach is to shallow rake the existing mulch to restore a freshly mulched appearance.

Mulch entire plant beds with a layer of mulching material. Provide a 2- to 3-inch layer of mulch at the base of newly installed plants. When mulching individual trees in lawns, create a circle of mulch about 2 feet in diameter for each inch of trunk diameter. Increase the size of the mulched area as the tree grows. Pull mulch 1 to 2 inches away from the stems and trunks of plants. The high moisture environment created by mulch increases the chances of stem or trunk rot which can result in plant death. Mulching dooryard citrus trees is not normally recommended as mulching may increase the incidence of root rot.  If citrus is mulched, the mulch should be kept about a foot away from the trunk.

In addition to being useful around plants, mulch can be used as a ground cover to protect and beautify  walks, trails, driveways, and play and natural areas. It can be used temporarily to cover low-growing tender plants to protect them from frost injury.

The amount of mulch to apply will depend on the texture and density of the mulch. Many wood and bark mulches are composed of fine particles and should not be more than 2 to 3 inches deep after settling. Excessive amounts of these fine-textured mulches around shallow-rooted plants can
deprive their roots of oxygen causing chlorosis and poor growth. Course-textured mulches such as pine needles and pine bark nuggets, which allow good air movement through them, can be maintained as deep as 4 inches.

Mulches composed solely of shredded leaves, small leaves (oak leaves), or grass clippings should
never exceed a 2-inch depth. These materials have flat surfaces and tend to mat together, restricting the water and air supply to plant roots.

The cost of mulch is quickly recovered in labor saved and benefits to your plants.  Mulching is really an adaptation of the natural process of leaves and other plant materials falling to the earth recycling nutrients.  Utilizing this practice in your garden can result in a more beautiful, more rewarding landscape.  Good luck and good gardening.

Gene McAvoy is the horticulture agent with the Hendry County Extension Service.  Direct your horticulture questions to PO Box 68, LaBelle, FL 33975,  e-mail - or phone 863-674-4092 or 863-983-1598.  You are also welcome to visit the Hendry County Extension Office at 225 Pratt Blvd., LaBelle.   Office hours are from 8:00 - 5:00.

The Institute of Food and Agricultural Sciences is an Equal Employment Opportunity - Affirmative Action Employer authorized to provide research, educational information and other services only to individuals and institutions that function without regard to race, color, sex, age, handicap or national origin.

Home                    Index