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How To Get Rid Of Onion Grass – 6 Methods

Onion grass is an upright herbaceous perennial plant in the Lilac family, which grows to about 30 to 60 cm, but sometimes goes up to 1 m. It abundantly grows in the southeastern United States.

You can find onion grass in prairie remnants and areas along the railroads, near the rivers, degraded meadows, woodland borders, vacant lots, poorly maintained lawns, and more. The grass prefers heavy soils with clay. But other types of soil are also tolerated.

The Roots of Onion Grass

The main underground structure is the bulbs that have fibrous roots to the bottom. The bulbs are rounded or oval and are covered with a papery, membranous, brittle outer layer.

The mature bulb produces two types of underground bulbs at the bottom. This includes soft-coated bulbs, which are teardrop-shaped and white and can sprout in the first fall. Also, hard-coated bulbs are oval, light brown, flat on one side, and sprouts later or the following spring.

How To Get Rid Of Onion Grass 2


The onion grass has smooth and waxy stems, erect, unbranched, thin, rounded, and hairless, and can grow between 1 and 3 1/2 feet tall. The stems are generally rigid and solid over time.


The leaves at the base protrude from the bulbs and are between 1/2 and 2 meters long. They are thin, hollow, smooth, and almost round in the cross-section.

The stem leaves form along the bottom, consist of the tubular sheath around the stem, and have a hollow, smooth, and grass-like blade. There are blades, which are flat at the bottom, but almost rounded at the end. Also, the sheath covers the bottom of the stem.


The aerial bulblets or flowers are produced in thick spherical clusters at the stems on top and are between 3/4 and 2 inches. These clusters are first covered with the paper bract.

The flowers are purple or greenish, with six small petals, and grow on short stems above the bulbs. They are teardrop or oval-shaped and very small, with a height of between 1/8 and 1/5 inches.

Also, they are shiny, smooth, and often develop small, tail-shaped green leaves. The flowering usually takes place between June and July.

Seeds and fruits

The flowers produce 2-seeded fruits in small egg-shaped capsules, which are about 3 to 4 mm long. The seeds are also around 3 to 4mm long, flat. Likewise, they are dark black and wrinkled, and flattened on one side. The seeds begin to ripen between August and September.

Is Onion Grass Harmful?

Like any other weed, onion grass can interfere with the growth of the plants in your garden, mainly if you are doing nothing to get rid of them.

The worst thing is that they can spread as they multiply in different ways: growing bulbs underground, dropping seeds, and more. They are nasty weeds, and it will be more challenging to remove them later if you do not stop them soon.

If you want to get rid of weeds, for example, by digging them up, shake off extra dirt and the many bulblets attached to bigger bulbs at the grass root, and they will be no more.

How To Get Rid Of Onion Grass

The problem with many weeds is that they’re more aggressive and more robust than most of the essential plants that are in the garden. Onion grass usually germinates and propagate quickly on their own, and once rooted it is challenging to kill them.

When deciding how to remove onion grass, you need to consider various methods available which work best for your case. The following options are ways on how to get rid of them, which many people can use.

1. Pull Up the Onion Grass in Clumps

The onion grass usually grows in clumps, and you can pull them out by hand or remove them with a trowel or a hoe. This is a tiresome method and is always ineffective if you’re not careful when removing and discarding grass completely.

It may be necessary to dig six inches down to remove all bulbs, and it’s paramount to dispose of them in a place that prevents the seeds from spreading into the garden again.

Pull Up the Onion Grass in Clumps How To Get Rid Of Onion Grass

2. Apply 2,4-D Amine

2,4-D Amine is an effective selective herbicide that can be used to get rid of onion grass. Selective means it only harms the targeted weed and does not harm the plants surrounding the desired weed.

You need to measure one square meter of the area to be treated to see how much 2,4-D Amine you will require. This herbicide is supposed to be mixed with one liter of water in a proportion of 0.75 fl. oz to 1 fl. oz. per 1000 sq. ft.

Mixing 2-4-D Amine with the surfactant such as Alligare 90 will assist the product to adhere better to grass and make the weed killer more effective.

Apply 24 D Amine - How To Get Rid Of Onion Grass
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For instance, if you have 2000 square feet to treat, you should mix between 1.5 and 2 fl. oz. in 2 liters of water.

Once the measurement is complete, and the amount of 2,4-D Amine needed, mix the surfactant and product with the proper amount of water in a backpack or handheld sprayer.

Shake the sprayer very well to make sure the solution has integrated well and ready to spray. During application, replace the nozzle set with the fan nozzle to spray the fine mist onto the plant and achieve even coverage on the onion grass.

3. Soil acidity

Plants like onion grass, unlike many types of grass, love acidic soils. If the ground is acidic other lawns can struggle, but onion grass will flourish.

Fertilizing the lawn and soil to create the optimal pH and nutrients can improve garden and lawn health and reduce acidity.

The ground balance can make the garden less attractive to the onion grass, particularly if you have a thick and healthy lawn with a robust root system. With time onion grass will be no more.

4. Use Roundup

To get rid of onion grass, use Roundup during the early fall when they are first noticed. Also, note that you can make another application during the spring period.

For the small patches of the onion grass, it is recommended to use ready-made versions of the product, but if the grass has spread widely, opt for a concentrate or ready-to-spray version.

Typically, use these sprays after and before winter, as onions are perennial. Bulbs hang below the surface in winter before germinating in spring.

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5. Overseed or Sod the Lawn

If your onion grass has overtaken the lawn, it can be challenging to eliminate them all. The best way can be to make sure the grass is healthy. Aerating, fertilizing, and overseeding your lawn can help restore healthy grass, which will push onion out of the garden.

If there are many of these weeds, it’s a good idea to start with the sod initially. Plowing the lawn, treating it with an herbicide, and starting a new grass can end the onion grass problem.

6. Cover the Area with Herbicide-Free Plastic

Take an opaque black plastic sheet, which is big enough to cover the onion grass area. Use more sheets as needed, hold the opaque black plastic in place with stakes or rocks, and leave it for several weeks.

Cutting off the light necessary for plants to survive will kill onion grass. Also, this method can dry out the soil and will eventually get rid of onion grasses. It would be best if you allowed the ground and surface to normalize for a year or more.

Health Benefits of Onion Grass

  • Bone health: About 70 grams of onion grass provide the recommended daily intake of vitamin K that has the potential role in bone health through strengthening activity and promoting bone formation. Adequate amounts of vitamin K in food help limit damage to the brain’s nerve cells, displaying the established role in treating Alzheimer’s disease.
  • Protect the brain and heart: Onion grass reduces the stiffness of blood vessels by releasing nitric oxide and lowering blood pressure. It prevents platelets from clotting and has a fibrinolytic effect on blood vessels, helping to reduce the overall risk of peripheral vascular disease, stroke, and coronary artery disease. Also, it reduces insufficient cholesterol production and makes the liver very happy. Besides, there are powerful antiviral, antibacterial, and anti-fungal properties.
  • Inhibit cancer growth: Onion grass leaf extracts have been revealed to inhibit the growth of many types of cancers, like breast, colon, and lung cancers. By the way, it is more valuable than ordinary garlic.
  • Solve gut health problems: Like the cultivated relatives, onion grass can be beneficial for gut flora. The gut flora affects many aspects of physical and mental health.


Onion grasses are herbaceous perennial plants, which are found in many parts of the world. They come from the family of bulbous and tastes similar to onions and chives. Also, they are rarely eaten and are considered weeds because of their invasion.

If you want to get rid of them, you need to be careful because a small bulb can make them grow again. There are different methods like pulling up by hand, applying 2,4-D Amine, overseeding the lawn, and more.