By Paul Schnare
Monday, September 29, 2003
As you drive around the Heartland, you see that most landscape beds are covered with some sort of mulch. Although many people consider decorative gravels as mulch, I would like to define landscape mulch as an organic material that is used as a ground cover. There are a number of different mulches to choose from. Perhaps I can help you discover the facts about different mulches and make your selection a little easier.
Mulches are used in landscape beds for a myriad of different reasons. First, mulch enhances the aesthetic look of a landscape. In addition a thick layer of mulch helps hold moisture in the soil. This water holding capacity is especially important during droughts and when trees and shrubs are first planted.
Probably one of the most important reasons to use mulch is to control weeds that seem to continually come up in your landscape beds. Mulch also controls erosion that could develop if the soils between shrubs would remain bare.
Mulch keeps plant roots cool during the hot part of the summer and warm during the coldest parts of the winter. In addition, mulch around a tree or shrub seems to be a visible barrier for the weedeater operator who wants to get as close as possible to trees and shrubs.
Of all the different kinds of mulch available, hardwood bark mulch seems to be the most popular, undoubtedly due to is low cost. It is the least expensive mulch found in the Heartland. Every sawmill in the Heartland produces hardwood bark mulch as a bi-product of the milling operation. Because it is so plentiful and local, hardwood buck mulch seems to be the mulch of choice.
There are some drawbacks to hardwood bark mulch. Pest control companies say that this mulch attracts termites. I doubt that it attracts termites, but there is no natural termite repellent in hardwood bark mulch. If termites are in the area, they will certainly like the addition to their home range.
Hardwood bark mulch tends to deteriorate rapidly, and often forms an impervious layer on the surface of the mulch bed. This impervious layer often contributes to the demise of azaleas and rhododendrons.
Cedar and cypress mulches are also available in the Heartland. Both of these woods have natural insect repellents present. In addition these mulches do not breakdown as rapidly as hardwood bark mulch.
Many gardeners like to use pine bark mulch, pine mini nuggets, or pine nuggets. The mulch is similar in appearance of hardwood bark mulch, but it does not form an impervious layer, as does hardwood bark mulch. The nuggets and mini nuggets are just larger particles of bark, great for use around azaleas and rhododendrons. Unfortunately the nuggets and mini nuggets blow in the wind and can be moved easily during a heavy rainstorm.
More and more azaleas and rhododendron growers are using pine needles as mulch. In southeastern United States, pine needles as used quite extensively, probably due to their abundance and low cost. In addition, leachates from pine needles keep the pH of the soil close to 5.0. Low pH is just what azaleas like.
If you want to have the sweetest landscape in town, try using cocoa bean mulch. This mulch is derived from the husks of cocoa beans. Its small particle size gives your landscape mulch a more formal look. It usually stays where you placed it no matter what the weather. Its only drawback seems to be cost.
I have just mentioned a few mulches that you can find on the market. In addition to the ones mentioned you can use gravels, colored mulch which is ground up used pallets and dyed, rubber mulch which is ground up used tires, leaves, grass clippings, sawdust, and wood chips.
Let me caution you about using mulch with a high content of wood or undecomposed leaf matter. The fungi that decompose wood and leaf matter require a lot of nitrogen to do their thing. This nitrogen is absorbed from the soil below the mulch. The depletion of soil nitrogen can be extremely detrimental to shrubs and trees growing in the raw mulch.
When you mulch use about a three to four inch layer. Make sure you keep the mulch an inch or two away from the stem of trees and shrubs. If you put the mulch up on the stem, the stem will slow rot due to all of the excess moisture, and your trees and shrubs will slowly die.
Mulch is not always a cure all. Its presence can cause problems. If your area is naturally wet, layers of mulch will inhibit soil drying. Plants in that area can actually drown during wet seasons.
Be sure you know what the mulch will do to soil pH, and the pH requirements of the plants in your landscape. As mentioned above pine needles will reduce the soil pH to about 5.0. Hardwood bark mulch usually keeps the pH around 5.5 to 6.0.
One other problem shows up in hardwood bark mulch. Sometimes fungi grow on the mulch in warm wet weather. This disgusting looking fungus looks like an animal vomited in your landscape. In order to reduce this problem, occasionally stir the mulch to allow air to get into it. This should reduce the fungus problem.
I have given you a lot of information about organic mulch. I hope this helps you select the right mulch for your landscape.