When to Use Crabgrass Preventer on Fescue

Ingenious Weed Reproduction

• As an annual, crabgrass grows vigorously with the warming spring and produces many seeds as summer turns to fall. Although dieback occurs as cold weather sets in, crabgrass seeds lay dormant until next spring when they repopulate the area. Planning your weed control with a well-timed crabgrass preventer in the early spring is the best way to eradicate this pesky plant before it even germinates.

Spring Into Action

• Apply crabgrass preventer in the spring when temperatures remain between 65 and 70 degrees Fahrenheit for more than three days. This temperature range reduces chemical loss to vaporization or improper soil absorption on hot or cold days, respectively. Fescue contributes to crabgrass control because it actively grows in early spring, benefiting your soil with dense coverage to shade out potential weed seedlings. Depending on the chemical mixture, crabgrass preventers impede seed germination from four to 12 weeks. For persistent crabgrass growth, reapply the preventer two more times in four-week intervals to continually control weed germination. This time frame coincides with crabgrass' main germination and growth period, making it difficult for this weed to establish itself in the lawn.

Is It Fall Already?

• If you are unable to apply preventer in the spring, do not use it in the fall as a last resort. Because crabgrass dies back in the fall, the preventer is simply wasted as it runs off with autumn rainfall. Fescue overseeding is typically done in the fall as well. Combining preemergent herbicide and new grass seed creates poor growing conditions that often result in failed germination. Allow winter cold to kill off your pesky crabgrass and begin control again in the spring when fescue is well-established and dense.

Battle It Out

• When fescue actively grows, maintain a grass height of 2 1/2 to 3 1/2 inches, to compete with potential weeds. This clumping grass needs long blades to photosynthesize during the waning fall months. Tall grass also impedes crabgrass growth because seedlings cannot access ample sunlight to spread rapidly. Deep fescue roots crowd out future shallow crabgrass roots as well, making control easier in the spring when weed seeds try to populate the yard.