view counter

Fighting Weeds?

There are better ways than mulch

Do you think the only method of controlling weeds is mulching?
    If so, you’re likely to add another layer of mulch every time you see weeds growing through the last layer. From there on, mulching becomes a habit.
    Mulches control weeds by suffocation and by shading the soil, thus denying the weed seeds the red waves of sunlight. The red wave band of the sun’s spectrum stimulates weed seeds to ­germinate.
    But thick layers of mulch also prevent oxygen, necessary for good plant root growth, from entering the soil. Thick layers of mulch also absorb the first quarter-inch of rain or irrigation, keeping it from reaching the soil.
    Never apply a layer more than an inch or two deep each per year. Before applying a new layer, always incorporate the previous year’s mulch into the surface soil. Where azaleas, rhododendrons and mountain laurels are growing, it is best to remove the old layer. Pine bark is the exception; incorporating it with a steel rake may be adequate.
    If the color of the old mulch is not satisfactory, consider spraying it with liquid mulch. Liquid mulches in the same dies used to color the raw wood chips are available from suppliers such as A.M. Leonard.
    If weeds are a severe problem, consider covering the ground with landscape fabric before applying mulch. However, if Bermuda grass, pigweed or nutsedge are present, these must be irradiated before applying the landscape fabric because they will grow through the fabric, making it impossible to remove.
    Avoid using black plastic around shallow-rooted plants. Unlike landscape fabric, plastic inhibits the movement of oxygen into the soil.
    Small weeds in the landscape can be controlled by spraying with horticultural vinegar. Horticultural vinegar contains 20 percent acetic acid and will kill weeds up to about three inches tall. It is also available from A.M. Leonard. If the acetic acid accidently comes in contact with the foliage of desirable perennials, it will not cause any permanent damage.
    Before you use an herbicide, know how it works. Preen, for example, is a preemergent herbicide you can use only on clean cultivated soil. As it contains only fluoride, it kills primarily germinating seeds of grass and only a few broadleaf weeds. So it is safe to use near and around ornamental plants, but it is effective for no more than six weeks. Always follow manufacturer’s recommendations when applying any herbicide.


Ask Dr. Gouin your questions at DR.FRGouin@gmail.com. Please include your name and address.