How to Kill Grassy Weeds

Have a problem with annual grassy weeds like crabgrass?

Let's face it: You don't fertilize, water, and mow your lawn to make it attractive to weeds. Yet that's how a lot of people feel when they see weeds like crabgrass take over. Annual grassy weeds are quick growing plants that thrive in the stressed areas of your yard. Thin, dried-out, or sun-scorched areas of your lawn are inviting spots for grassy weeds. The best way to fight them is to learn how they grow and then deprive them.

What Are Annual Grassy Weeds?

The most common annual grassy weeds you'll find in your yard are crabgrass, goosegrass, foxtail, and barnyardgrass. These weeds only live for one growing season. They sprout from seeds in spring when the soil temperatures reach 55-60 degrees F. Then they grow quickly from late spring to summer when they flower and form seed that will sprout the following spring. Annual grassy weeds are killed by the first frost of fall. Because they reproduce entirely by seed, they are prolific – each plant can produce thousands of seeds.

How to Prevent and Kill Grassy Weeds

Many annual grassy weeds like crabgrass and foxtail can be prevented from developing by applying a pre-emergent herbicide in early to mid-spring. However, once they have sprouted, there are control products available that will kill them later in the year. If you only have a few pop-up annual grassy weeds, they are best controlled with Ortho® WeedClear™ Lawn Weed Killer Ready-to-Use. However, if your annual grassy weed problem is widespread, use Ortho® WeedClear™ Lawn Weed Killer Ready-to-Spray or Ortho® WeedClear™ Lawn Weed Killer Concentrate applied with an Ortho® Dial ‘N Spray instead.

If you also have grassy weeds rearing their ugly heads in your landscape beds, spot-treat them with Ortho® GroundClear® Super Weed & Grass Killer. It is always best to treat annual grassy weeds when they are small and actively growing, before they flower, but (when used as directed) this hard-hitting formula will kill them at their roots at any stage.

More Ways to Control Grassy Weeds

The way to keep grassy weeds out of your lawn is to make them feel unwelcome in the first place. A thick, lush lawn doesn't leave any space for weeds to grow. To keep annual grassy weeds at bay, follow these maintenance tips:

Mow High

Always mow your lawn at the proper height (for most lawns this is usually one of the highest settings on your mower). Longer grass blades shade the soil, helping prevent weed seeds from germinating. Scalping your lawn (mowing too short), thins your lawn and makes it more prone to weeds.

Fertilize Regularly

When your lawn is stressed from being under-nourished, it is more prone to being taken over by weeds. Regular feedings every 6-8 weeks during the growing season with a lawn fertilizer helps your lawn stay thick and lush.

Water Deeply

Watering deeply and infrequently (allowing the soil to dry down between waterings) helps your lawn grow deeper roots so it can better compete with weeds. Frequent, quick waterings encourage shallow root growth. During periods of high heat and drought, the grass is more prone to damage causing thin or bare spots that weeds will take advantage of.

Repair Bare Spots

When annual grassy weeds are killed in the fall by frost, they leave behind bare spots. Patching these spots with grass seed will help keep new weeds out.