Dedicated gardeners who have been gardening for several years know firsthand how valuable mulches are and most of them would not even consider growing any kind of garden unless they had a good mulch to use. So, just what do mulches accomplish? Actually, mulches serve several different purposes. Possibly the most important of these is the suppression of weeds which compete with our plants for the nutrients in the soil as well as the water that’s there. Competing weeds typically grow faster than most of the plants we place in our gardens and unchecked quickly become taller than the flowers or vegetables thus shading outcrop plants and robbing them of the necessary sunlight. Another purpose that organic mulches bring to the garden is enriching the soil as they decompose plus enhancing the environment for beneficial soil microorganisms.
So, what are some of the materials that can be used as a mulch? Several pages of old newspapers placed on the soil surface and wet down to make them heavy enough to avoid blowing away in a moderate wind have long been used by many gardeners. Re-wetting them may become necessary if rains are too far apart, but that problem can easily be corrected by the use of sprinkler irrigation. Some gardeners have successfully used old heavily soiled carpets for mulches. Just cut the carpet in strips the width of the space between rows. After the carpet has served its role as a mulch, it can be removed and disposed of. Like the newspaper, it will suppress weeds and will also help maintain soil moisture. But unlike the newspaper, it is usually heavy enough (wet or dry) to stay in place on windy days.
Black plastic mulch excludes light and thus robs the weeds of the sun’s energy they need to survive. Another benefit is that it warms the soil while spring temperatures are still cool and when applied relatively early will make flowers and vegetables grow somewhat faster so that maturity is reached sooner. It also helps keep the soil from packing during heavy rains and acts as an umbrella on raised rows thereby preventing soil saturation. Unfortunately, it has some disadvantages. It’s an added cost, as it ages it breaks into small pieces that are difficult to remove from the soil, it may be hard to find and it becomes a haven for fire ants. Also, it must be anchored on the ends and edges to prevent the wind from getting under it and blowing it away.
Probably more gardeners use organic mulches then any other kind, but not all are the best choice for certain situations. Wood chips or shavings, grain straw, shredded bark and gin trash are some of the most common mulching materials. If sufficiently thick, they suppress weeds, insulate the soil from extreme temperatures, enrich the soil, create a better environment for beneficial soil microorganisms and improve the physical properties of many different soil types.
Joe White is a retired horticulturist with the LSU AgCenter.