When the milder weather arrives, it’s the perfect time to start the spring yard cleanup and prepare our plants and lawns for the peak growing season.

It’s difficult to forget to tidy flowerbeds, prune shrubs, divide perennials, and rake lawns—they’re all obvious eyesores. Some tasks are less obvious, but neglecting to do them can result in long-term landscaping problems. 

According to professional agronomist Marc Mayer, there’s one spring lawn care mistake he wants you to avoid. Overlooking appropriate weed control measures can be the difference between cultivating a lush lawn and one that’s thin, brown and overrun.

Why Is Forgetting Pre-Emergent Weed Treatment a Mistake?

Mayer explains that failing to apply a pre-emergent weed treatment to your lawn can cause major issues down the line. Fast-growing weeds compete with your grass for nutrients, water, and space.

“This competition can smother the grass, disrupt its growth, and leave your lawn looking patchy and unhealthy,” he says.

The goal of using a pre-emergent herbicide at the right time is to prevent broadleaf weed seeds from germinating and establishing roots.

“This leads to the weed not being able to absorb nutrients and stops all growth,” Mayer says. 

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When to Apply Pre-Emergent Weed Treatment to Lawns

If you use pre-emergent herbicides in spring, Mayer recommends applying the treatment before the soil hits 55°F to 60°F. He explains this will help you get ahead of warm-season weeds before they start growing and establish roots, reducing their populations during the growing season.

This exact timing depends on your location and USDA hardiness zone, but the window is usually between late February and mid-March.

Which Pre-Emergent Weed Treatment to Use

There’s a wide range of treatments out there.

“The specific type of pre-emergent herbicide you use may depend on the grass type (cool-season vs. warm-season) and local weed species,” Mayer says.

Always read the label to avoid selecting an active ingredient that can damage your turfgrass type.

You’ll have to choose between a liquid or granular formula and ensure you have enough to cover your lawn square footage. Liquid formulas are often considered easier to apply and more effective. 

How to Apply Pre-Emergent Weed Treatment to Lawns

How you apply pre-emergent weed treatment is just as important as when—and getting it right can be tricky. Application methods vary depending on the type of herbicide you use and its format (liquid or granular). Always read the label so you can apply the treatment effectively and safely. However, here are some handy general application tips to keep in mind:

• Most pre-emergent herbicides need watering into dry soil.
• They won’t be effective in areas of standing water or when soils are already excessively soggy. 
• Using a hose with a sprinkler nozzle to water in across a large lawn is easiest.
• Don’t spray liquid pre-emergents when there are high winds, and spray close to the ground.
• Be careful about where you apply the treatment—you could inadvertently affect the germinating seeds of desired plants.

What to Do if You Forget to Apply Pre-Emergent Weed Treatment to Lawns

If weeds have already emerged, applying a pre-emergent won’t kill them. Mayer recommends applying a post-emergent herbicide to control common lawn weeds instead. Doing this early will help prevent the weeds from smothering your grass.  

“Post-emergent treatments are designed to target specific weeds, so apply them carefully to prevent harm to nearby grass,” Mayer warns. “Also, make sure you prioritize maintaining a healthy lawn, as those that are fertilized and lush will keep weeds from germinating.”

Alternatives to Pre-Emergent Weed Treatments

While pre-emergent herbicides can keep unwanted lawn interlopers away, they are chemical treatments that aren’t usually environmentally friendly. If you want a green solution to achieve a green lawn, consider the following non-chemical weed control options instead:

• Manual weeding: “Hand-pulling weeds or using a weeding tool is one of the most effective non-chemical methods,” Mayer says. Although it’s probably best to reserve this for small patches of weeds—otherwise, you could be at it a long time and have a very sore back by the time you finish.
• Promote a healthy lawn: “Regular mowing, watering, and fertilizing helps grass grow thickly,” Mayer says. Weeds won’t be able to compete so easily for space, light and nutrients when your lawn is thick and verdant.
• Aerate your lawn: This improves soil structure, helping to support a healthy lawn.