Is Pesky Wild Onion Grass Taking Over Your Lawn? Time to Get Rid of It

The onions and garlic you buy at the grocery store have a pesky relative that can show up on lawns in various climates. These smelly weeds can be tricky to eliminate, but a few removal methods are effective. Follow this DIY weed control guide to properly identify onion grass, remove it from your lawn or garden, and prevent it from returning.

What Is Lawn Onion Grass?

Wild onion grass, and the very similar wild garlic, are both stubborn weeds that can invade lawns of all types. These winter-blooming weeds creep up in flower beds or lawns, spreading quickly by reseeding and reproducing under the soil.

While weeds can be a nuisance, it’s essential to know what you’re dealing with before starting any kind of treatment. Misidentifying your problem weed can lead to using the wrong methods, which will waste time and money. Look for the traits below to identify wild onions in your yard:

• Thick, grass-like appearance: The thin, waxy, spear-shaped leaves of onion grass grow in tall clusters up to 2-feet long with white or pale pink star-shaped flowers.

• Looks and smells like onions: Onion grass grows from white bulbs under the soil that give off a strong onion-like smell.

• Multiple patches: Onion grass can reproduce quickly, producing bulbs and seeds that tend to pop up in more than one spot.

Wild onion is often mistaken for wild garlic, which has longer, thinner, hollow tube-like leaves. Wild onion leaves tend to be flat, wide, and long. If you’re still not sure about the weed you’re looking at, you can contact a lawn care service near you to help you correctly identify the weeds in your lawn and provide treatment recommendations.

How to Kill Onion Grass

Once you’ve confirmed that you have wild onion grass, inspect your lawn and garden to pinpoint the areas where the weed is growing. Look for thick clumps of grass with a strong onion smell that are waxy to the touch. Once you’ve narrowed down your problem areas, choose one of the effective removal methods detailed below.

Dig the Onion Grass Out by Hand

Onion weed can’t simply be mowed down or pulled up since the underground bulbs will grow new leaves within a few days. Instead, remove entire clumps with a weeding fork or trowel. Completely remove the root system by digging it up from below. Discard the entire clump in the trash so seeds can’t spread. This labor-intensive method of pulling weeds by hand works best for smaller invasions.

Chemical Control With a Selective Weed Killer

The most effective way to deal with a large onion grass invasion is with a selective weed killer labeled to treat wild onion. This type of herbicide will only harm the weed and not the desired grasses and other plants around it. Before handling any herbicide, wear a safety mask, goggles, and protective gloves to avoid bodily contact with the chemicals.

Treat the weeds in early to mid-fall. You can mix your herbicide with a surfactant to help it stick better to the waxy weed and work more effectively. Mix your solution in a handheld or backpack sprayer according to the instructions on the packaging. Set the nozzle to a fan setting to create a fine mist that evenly coats the wild onion weeds.

How to Prevent Onion Weed From Growing

Onion weed prevention requires persistence and patience. Once you’ve removed onion grass from your lawn or garden, you’ll need to use preventive measures to keep it from making a comeback. Monitor your lawn closely throughout the year and take immediate action at the first sight of new onion grass, removing small patches by hand as they appear.

If your initial fall application of weed killer didn’t eliminate the problem, follow up with another in late winter or early spring. However, avoid applying weed killer to centipede grass or St. Augustine grass during the spring months. You may need to repeat the application process for a few years since bulbs can stay dormant in the soil for six years.