4 Natural Ways to Get Rid of Onion Grass—and Prevent It From Coming Back

Few things thwart your efforts for a lush, healthy landscape quite like onion grass. This unsightly weed is an aggressive grower that outcompetes turf for water, nutrients, and sunlight, resulting in a stressed lawn with bald patches. While onion grass is difficult to eradicate, it's not impossible, and it can even be accomplished using natural household products, like vinegar. Ahead, a gardening and landscape expert share their tips for removing onion grass—without using synthetic chemicals.

What Is Onion Grass?

Onion grass, also known as wild onion or wild garlic, is a cool-season, perennial, broadleaf weed that grows from underground bulbs. "These bulbs allow the plant to survive harsh conditions. The leaves have a waxy coating, which makes it difficult for chemicals to penetrate," says Linda Langelo, horticulture specialist at Colorado State University. "The root systems are fibrous and extensive." Onion grass bulbs remain dormant in the soil and, when conditions are ideal in fall and early spring, they emerge, filling gardens with their un-slightly, grass-like foliage. 

When to Treat Onion Grass 

Treat onion grass in early spring or when it reappears in fall. “In the fall, all plants are storing carbohydrate reserves for winter survival,” says Langelo. “Plants naturally pull nutrients into their root systems. This is an ideal time to treat the onion grass to get it into the root system more quickly.” When top growth reappears in spring, treat the weed again. “Remember to treat it as aggressively as the onion grass is growing. Persistence wins,” Langelo urges. 

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Natural Ways to Get Rid of Onion Grass

These invasive weeds are fast-growing and rob your grass of water, nutrients, and sunlight, weakening your garden over time, says Brian Feldman, senior director of technical operations at TruGreen. Onion grass is difficult to eradicate, but organic weed control options can be effective, as long as homeowners are diligent. 

Hand-Pull Them

Hand-pulling weeds is an effective solution for isolated weeds. For this, Langelo recommends moistening the soil to make the weeds easier to pull. Wrap your hand around the weed and pull, ensuring the entire root system and the bulb are removed. You can also use a shovel or digging fork to make removal easier. While this works for minor weed issues, Feldman notes that it’s time-consuming and rarely effective for widespread problems. 

Use Corn Gluten 

Corn gluten, a byproduct of corn processing, can treat onion grass. “Corn gluten meal acts as a natural, organic pre-emergent herbicide that inhibits root formation in germinating weed seeds, making it useful for reducing new populations of onion grass,” says Feldman. To apply it, Langelo says to spread the corn gluten over your yard in the spring and fall, then water well to ensure it penetrates the soil.

Apply a Vinegar Solution

Vinegar acts as a non-selective herbicide, killing foliage upon contact. “It works by breaking down the waxy cuticle on the leaf surface, leading to rapid dehydration,” says Feldman. For this, combine 1 gallon vinegar, 1 tablespoon dish soap, and 1 cup salt in a spray bottle. Spray the mixture directly onto the onion grass, ensuring it doesn’t touch nearby grass or plants or it will kill those as well.  

Use Boiling Water 

Similar to vinegar, boiling water acts as a non-selective herbicide. Bring water to a boil, then pour it over the onion grass, avoiding surrounding plants. "This will cause the leaf tissue to collapse immediately," says Langelo. “This only works if it is done repeatedly. You must do it enough to reach the root system, which depends on the size of the onion grass plant and its extensive root system.”

How to Prevent Onion Grass From Returning 

Removing onion grass from your yard is only part of the process—preventing it from returning requires consistent lawn care and proper maintenance, Feldman explains. Maintaining healthy, dense turf is the secret to keeping onion grass away. “Aerate the lawn twice a year and overseed when necessary to fill in any gaps in the lawn,” says Langelo. She also recommends fertilizing in the fall to promote a healthier root system, watering deeply and infrequently, and mowing at the proper height with sharp blades. Feldman adds that homeowners should overseed thin areas to reduce open spaces where weeds can take hold.