Daniel Gill, Merrill, Thomas A.
Mulching makes gardening easier, and I think more gardeners should take advantage of this important labor-saving technique.
A mulch can be an organic or inorganic material used to cover the soil surface around plants.
Organic mulches are the most popular. These mulches, such as leaves, chopped leaves, pine straw, ground pine bark, dry grass clippings and newspaper, all are derived from once-living materials. They are popular for their ease of use, attractive appearance (except for newspaper) and because, as they decompose, they add beneficial organic matter to the soil.
Inorganic mulches are derived from nonliving sources and include such materials as plastic sheeting, landscape fabric or weed barriers, stone chips, gravel or even carpet remnants. Many of these mulches are not very attractive and are only suitable in more utilitarian situations such as a vegetable garden. In such an area, carpet remnants work very well in walkways. In more decorative areas, unattractive inorganic mulches, such as landscape fabric, may be covered with a layer of organic mulch for appearances.
The first and foremost reason to use mulches is to control weeds. Whoever said "A job well done doesn’t have to be done again" never weeded a garden. Every time weeds are removed, new weed seeds germinate – creating the problem all over again.
Mulches work to stop this process by blocking light from reaching the soil surface. Most weed seeds need light to germinate, since that tells them they are close enough to the soil surface to sprout and grow. When covered over with mulch, they think they’re still deep in the soil and will not germinate.
To create this barrier to weed growth, organic mulches have to be applied thick enough to do the job. Too often, gardeners spread mulch as thin as possible – just to cover the soil. This will not be effective in preventing weeds. Apply organic mulches at least 2-inches thick for best weed control.
Organic mulches are not as effective in controlling persistent perennial weeds such as nutsedge, oxalis, Bermuda grass, torpedo grass and others that grow from below-ground bulbs or rhizomes – or that run into beds from surrounding areas – but they can help. Woven weed barriers or landscape fabric often do a better, though not perfect, job controlling these difficult weeds.
Another important function of mulches is conserving moisture in the soil. By slowing down evaporation from the soil surface, mulches keep beds from drying out as fast. This is especially important in hot, dry weather. Your plants receive a more-even supply of moisture, and you save money on your water bill. Shallow-rooted plants with limited root systems, such as bedding plants and vegetables in sunny areas, particularly benefit from mulches.
Organic mulches also insulate the soil and moderate soil temperatures – keeping the soil warmer in winter and cooler in summer – which help the roots. They can even reduce freeze injury to whatever part of the plant they cover in winter.
Black plastic used in the vegetable garden during winter and early spring helps to warm the soil by absorbing the heat of the sun. This keeps winter vegetables growing vigorously and allows for earlier planting of spring vegetables. As the weather warms up in April, black plastic mulch should be covered with an organic mulch to shade it and prevent excessive heat build-up.
On the other hand, black plastic should not be used to mulch permanent plantings, such as shrubs or around trees.
Have you ever worked hard to turn the soil in a bed until it is nice and loose only to watch rain and watering beat it down again until it’s just as hard and compacted as it was before? If you mulch as soon as you finish bed preparation and planting, you will find the mulch will substantially prevent soil compaction. A looser soil is easier for roots to grow through and absorbs water faster.
There is no one best mulch. Which one you choose depends on a variety of factors including the gardening situation, your preference based on appearance, what’s available, cost and durability.
I like to recycle yard waste such as leaves and dry grass clippings – using them as is or allowing them to partially compost before using them. They are cheap (free), effective and attractive.
If you are lucky enough to have access to free pine straw, it makes an ideal mulch. You also can purchase bales of pine straw rather economically or chopped pine straw by the bag.
If you currently are not using mulches in you gardening efforts, I strongly recommend you give them a try. You’ll be amazed at how much work they save you weeding and how nice they can make a garden look. If you are mulching, remember the primary function is not necessarily decorative and apply mulches thick enough throughout your landscape and gardens.
Get It Growing is a weekly feature on home lawn and garden topics prepared by experts in the LSU AgCenter. For more information on such topics, contact your parish LSU AgCenter Extension office or visit our Web site at www.lsuagcenter.com. A wide range of publications and a variety of other resources are available.