How To Get Rid Of Onion Grass

If you’ve noticed thin, green, onion-like shoots spreading through your lawn or garden, you’re likely dealing with a stubborn weed. Learning how to get rid of onion grass is key to reclaiming your green space. This perennial weed, also known as wild onion or garlic, can quickly become a nuisance with its bulbs and bulblets that multiply underground.

It’s not a true grass but a type of allium. It gives off a distint onion smell when mowed or crushed. Left unchecked, it can outcompete your desirable plants and create patchy, smelly areas in your lawn.

This guide will walk you through simple and effective methods, from manual removal to cultural controls.

There is no single magic bullet for eradicating onion grass. A persistant, multi-pronged approach works best. Your strategy will depend on where it’s growing—in a lawn, a vegetable bed, or a flower garden.

Consistency is your greatest ally. The goal is to exhaust the plant’s energy stored in its bulbs and prevent it from photosynthesizing.

Understanding Your Enemy: Why It’s So Tough

Onion grass is difficult to eliminate because of its reproductive strategy. It grows from bulbs and smaller bulblets underground. Each one can produce a new plant.

If you only pull off the top green part, the bulb remains in the soil to regrow. It also produces aerial bulblets at the top of its stems in late spring, which scatter and spread the weed further.

Knowing this lifecycle helps you time your attacks for maximum effect. The best times to tackle it are in spring and fall, when the plant is actively growing and sending energy to its roots.

Method 1: Manual Removal by Hand

For small infestations or in planting beds, hand-pulling is the most precise method. It’s immediate and avoids chemicals.

You must get the entire bulb out. Here’s how to do it effectively:

Water the area thoroughly the day before. This softens the soil and makes the bulbs easier to extract intact.
Use a weeding tool, like a dandelion digger or a narrow trowel. Insert it deep into the soil right next to the stem.
Lever the tool to loosen the soil and gently pull the entire plant, including the white bulb at the base. Try not to break the stem from the bulb.
Shake off excess soil and place all parts—greens, stems, and bulbs—into a bag for disposal. Do not compost them, as they may survive and spread.

This method requires patience, but it’s very effective if done carefully. You’ll need to monitor the area and repeat the process for any new shoots that appear from missed bulblets.

Method 2: Smothering and Solarizing

These are passive, non-chemical techniques that work well for larger, defined areas like a garden bed you plan to renovate.

Smothering (Sheet Mulching)

This cuts off light and starves the plants. It’s simple but takes several months.

Mow or cut the onion grass as short as possible.
Water the area.
Cover it completely with overlapping layers of cardboard or 8-10 sheets of newspaper. Eliminate all light.
Soak the paper/cardboard layer.
Top with 4-6 inches of mulch, like wood chips or straw. Leave it in place for an entire growing season.

Solarization

This uses the sun’s heat to “cook” the bulbs and bulblets. It works best in hot, sunny summer months.

Till or dig the area lightly to expose the soil.
Water deeply until the soil is moist.
Cover the area tightly with clear plastic sheeting. Bury the edges with soil to trap the heat.
Leave it sealed for 4-6 weeks during the hottest part of the summer. The heat will penetrate and kill the weed bulbs and seeds.

Method 3: Chemical Herbicide Options

In lawns, where manual removal is impractical for large infestations, herbicides may be necessary. Always choose the right product for your grass type and follow label instructions exactly.

Selective post-emergent herbicides are the primary tool. Look for products containing ingredients like 2,4-D, Dicamba, or MCPP. These broadleaf weed killers will target the onion grass without harming your lawn grass when used correctly.

Timing is Critical: Apply in fall or spring when the weed is actively growing and the weather is mild (55-85°F). Avoid applications during hot, stressful weather.
Follow-Up: You will likely need 2-3 applications spaced 2-3 weeks apart to kill new flushes that grow from underground bulbs.
Spot Treat: Instead of spraying the whole lawn, use a sprayer to apply herbicide only to the patches of onion grass. This minimizes chemical use.

For non-lawn areas like paths or driveways, a non-selective herbicide like glyphosate can be used. Be extreamly careful, as it will kill any plant it touches.

Method 4: Cultural Controls for Your Lawn

A thick, healthy lawn is your best long-term defense. Onion grass thrives in thin, weak, or compacted turf where it faces little competition.

Mow High: Keep your mower blade set to 3-4 inches. Taller grass shades the soil, making it harder for weed seedlings to establish.
Fertilize Appropriately: Feed your lawn based on a soil test. Proper nutrition encourages dense grass growth.
Core Aeration: Aerate your lawn annually to relieve soil compaction. This improves water and nutrient flow to grass roots.
Overseed: Every fall, spread grass seed over existing turf to fill in bare spots and thicken the lawn.
Water Deeply and Infrequently: Water your lawn thoroughly once a week rather than lightly every day. This encourages deep grass roots.

By improving your lawn’s overall health, you create an environment where grass outcompetes weeds naturally. It’s a slow but fundamental solution.

Preventing Onion Grass from Returning

Vigilance is key to prevention. Even after you think it’s gone, bulbs can linger.

Inspect your lawn and garden regularly, especially in early spring. Remove any new shoots immediately before they can multiply.
Clean your gardening tools, especially mower blades, after working in an infested area to avoid spreading bulblets.
When introducing new plants or soil to your garden, inspect them carefully for any weed stowaways.
Maintain those cultural practices for a thick lawn and healthy garden beds. A full, thriving planting leaves no room for invaders.

Remember, persistence pays off. It may take a full year or two of combined efforts to fully gain the upper hand.

Frequently Asked Questions (FAQ)

Is onion grass the same as wild garlic?

They are very closely related and often called by the same names. The easiest way to tell is by the leaves: onion grass has round, hollow leaves, while wild garlic has flat, solid leaves. Both smell like onions or garlic and the control methods are identical.

Can I eat onion grass from my yard?

While the above-ground green parts are technically edible and have an onion flavor, it is not recommended. Plants growing in lawns may have been treated with herbicides or chemicals you wouldn’t want to consume. They also could be contaminated from pets or environmental pollutants.

Why does my neighbor’s lawn not have this weed?

They likely have a thicker, healthier lawn due to good maintenance practices, or they have been consistant in removing it over time. Onion grass often starts from a few bulbs and spreads, so catching it early makes a huge difference.

Will vinegar kill onion grass?

Household vinegar may burn back the top growth, but it rarely kills the deep bulb. Horticultural vinegar (20% acetic acid) is more effective but is a non-selective, contact-only herbicide. It’s dangerous to use and can harm you and surrounding plants. It also doesn’t provide a reliable kill on perennial bulbs.

How deep do the bulbs go?

Typically, the main bulb is located 1 to 3 inches below the soil surface. However, smaller bulblets can be found even deeper, especially in soft, loose soil. That’s why digging is more effective than just pulling.

What is the fastest way to get rid of it?

For immediate results in a lawn, a combination of careful spot-treatment with a selective herbicide followed by diligent lawn care to fill in the gaps is the fastest approach. In garden beds, thorough hand-digging is the quickest way to see clear soil, though it requires effort.

Dealing with onion grass requires a bit of patience and a solid plan. By combining immediate removal tactics with long-term lawn and garden health strategies, you can win the battle. Start by identifying the scope of your problem, choose the methods that fit your space, and stay committed. With these simple and effective methods, you can restore the beauty and health of your outdoor space.