MSU Extension

The 2012 gardening season is well underway. Vegetable seeds and transplants are going into the ground with the expectation of a bountiful harvest by the fall. Before we can reap the rewards of our labor, all gardeners must run a gauntlet of challenges meant to prevent your harvest victories.

The chief among these challenges is weeds. More time can be and is spent on trying to control weeds than any other home gardening activity. This is particularly true if the weeds get a head start. One of the most effective ways to drastically reduce the time spent on weeding is by using mulches. Covering the ground with a mulch reduces the amount of light that reaches the soil surface which prevents or at least slows the germination of weed seeds.

There are a wide variety of mulches to choose from and, depending on the mulch selected, they have both advantages and disadvantages. Mulches can be used to increase or decrease soil temperatures, reduce the rate of moisture loss from the soil, increase crop yields, repel certain insects, slow the development of certain diseases, keep produce clean by preventing wet soil from splashing onto fruits and some add organic matter to the soil as they decompose. Mulches also have a few disadvantages. Organic mulches such as straws or hay can provide habitat for slugs.

Straw can contain wheat seeds which can become a problem. As hardwood chips decay, all manner of fungi can produce some interesting and disgusting mushrooms and the plants growing in a decaying mulch may require additional nitrogen applications for optimal growth.

Straw is an excellent mulch for crops that prefer cooler soil temperatures such as cabbage or broccoli, but it may slow the growth of warm season crops, such as tomatoes or melons. Straw mulch around squash, such as zucchini, in fall can result in greater damage to the plant after a light frost compared to squash on bare soil. When using straw, one large bale should easily cover 100 sq. ft. of area. If a six-layer newspaper mulch is placed on the ground before adding the straw, a larger area can be covered with one bale.

Landscape fabrics are great for warm season crops. The dark color will help to increase soil temperature faster under the fabric, which is beneficial to crops such as tomatoes, peppers, eggplant and melons. Melon yields can increase up to 50 percent when using either landscape fabric or dark colored plastics. Landscape fabrics are also a good investment since they can last 10 or more years and water can easily move through them and into the soil.

Most plastics mulches are impermeable and are designed for a single year use. Drip hoses or tape should be placed under the mulch to provide adequate moisture. Plastic mulches are available in a variety of colors including red, black, brown and metalized (reflective). Red is beneficial for tomatoes and strawberries. In the case of tomatoes, red mulch improves the quality of the fruit produced, but not necessarily the overall yield. The selective reflecting mulch like red has been shown in USDA tests to increase production from 12 to 20 percent of first quality, early tomatoes when compared to black mulch. The black and brown mulches provide the same benefits as landscape fabrics while reflective-metalized mulch tends to repel aphids. Reflective mulches are also being used to improve color on apples. Plastic mulches are subject to degradation from ultraviolet light. If they are not removed from the garden by the end of the season, they will become more brittle and difficult to remove.

Although wood mulches such as chipped hard and softwoods, cedar, cypress and pine bark aren’t used much in vegetable gardens, they can be used around perennial vegetables such as asparagus or rhubarb. Cedar and cypress will last the longest because they are resistant to decay. Chipped mixed woods will break down faster, especially if leaves are mixed in. These mulches should be applied to a depth of 2 to 3 inches on the perennial vegetables. Some of the wood mulches are painted for appearance. If you are growing vegetables organically avoid these products.

For additional information on mulches and other gardening topics, contact your local MSU Extension office, call 888-678-3464 or visit the Gardening in Michigan website.