Horticulture News: Controlling weeds before they arrive is best defense

By Amanda Sears/Madison County Horticulture Agent, Published:

Every year, a fierce battle is fought for supremacy in our lawns. Weeds often rear their ugly heads, sending you scrambling for the right herbicide to control their spread. Why not make the first strike by controlling crabgrass before it even germinates. Now until mid-April is the ideal time to do so.

Crabgrass is a summer annual grass that reproduces both by seed and by rooting at the lower joints of the stem. Growth looks different from other grasses in your yard. The stems are erect and arise from a creeping base that forms a mat. The blades are thicker than regular grass.

To control this weed, apply a pre-emergent herbicide to your lawn. This type of herbicide prevents weed seeds from germinating and is only effective if used prior to seed germination. If you wait until you see the weed growing, it is too late to use a pre-emergent herbicide.

Weeds that are grass-like are best controlled using this type of herbicide, while broadleaf weeds, such as dandelion, henbit, chickweed, or clover, are best controlled by post-emergent herbicides.

Crabgrass begins growing when soil temperatures are 60 degrees for three to five days. One way to remember when to apply a pre-emergent crabgrass control is before the Forsythia shrubs produce their yellow blooms early in the spring.

This is because the same environmental conditions that cause the bush to bloom also begin to trigger crabgrass growth. Use little or no fertilizer when applying the herbicide. Most pre-emergent weed control compounds provide protection for up to four to six weeks, so follow up applications can be useful to combat not only crabgrass, but also other warm season annuals.

For crabgrass control, look for products which may have one of the following active ingredients on the label: benefin/triflualin, pendimethalin, dithiopr, trifluralin, or prodiamine.

For more information on weed control in lawns, go to  www2.ca.uky.edu/agc/pubs/AGR/AGR208/AGR208.pdf.

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