How To Get Rid of Onion Grass?

Onion grass

Walking around your garden, you marvel at the colorful flowers that brighten your day.

But then you spot something that doesn’t belong—a sneaky grass with a strong onion odor.

You scrunch your face and ask yourself, “What is this thing?

But don’t fret; we have some solutions to ensure onion grass will never disturb your lawn or garden again.

In this article, you’d learn how to identify, dig out, spray, and prevent onion grass from invading your lawn and flower beds.

What Is Onion Grass?

Onion grass, also known as wild onion or wild garlic, is a perennial weed that belongs to the same family as onions, garlic, chives, and leeks.

Characteristics of Onion Grass

Onion grass has a strong onion or garlic smell and taste, which can be unpleasant for some people.

You can recognize it by its:

  • Long, thin, hollow leaves that grow from a white bulb.
  • In spring, it produces purple flowers that form clusters of seeds.

Problems Caused by Onion Grass

Onion grass is a problem for gardeners and landscapers because it can spread quickly and compete with other plants for nutrients and water.

It can also contaminate crops and pastures with its odor and flavor.

Onion grass is difficult to control because it has a deep root system that can regenerate new plants from small fragments.

It is also resistant to some herbicides and mowing.

Varieties of Onion Grass

There are different varieties of onion grass, such as:

  • Allium vineale has small bulbs that form chains underground and bulbils instead of seeds on the flower head.
  • Allium canadense, which has larger bulbs that are edible and seeds that are enclosed in papery capsules.
  • Allium triquetrum, which has triangular-shaped leaves and white flowers with green stripes.

However, they all share the same onion or garlic smell, taste, and invasive nature.

How To Identify Onion Grass?

Onion grass flower
Source: Plantnet

Before you can get rid of onion grass, you need to know how to recognize it.

Here are some tips to help you identify onion grass:

  • Look for long, thin, hollow leaves that grow in clumps from a white bulb. The leaves are usually dark green and smooth but may have a waxy coating or fine hair.
  • Smell the leaves or bulbs. They should have a strong onion or garlic odor that can be detected even from a distance.
  • Check the flowers and seeds. Onion grass flowers are usually purple and form round clusters on top of a tall stem. The black and shiny seeds may be attached to the flower head or enclosed in a capsule.

How To Dig Out Onion Grass?

Onion grass
Source: Wikimedia

Digging out onion grass is the most effective removal method because it eliminates the entire plant, including the bulb and the roots.

However, it can also be time-consuming and labor-intensive, especially if you have a large infestation.

Here are the steps to dig out onion grass.

Step #1: Loosen the Soil

Use a shovel or a garden fork to loosen the soil around the onion grass clumps.

This will make it easier to pull out the plants without breaking them.

Be careful not to damage any nearby plants that you want to keep.

Step #2: Pull Out the Plants

Use a trowel or your hands to pull out the onion grass plants by their base.

Try to get as much of the bulb and the roots as possible.

If the plants break, use the trowel to dig deeper and remove any remaining parts.

Shake off any excess soil from the plants.

Step #3: Repeat Until Clear

Repeat steps 1 and 2 until you have cleared all the onion grass from your garden.

You may need to do this several times throughout the season, as new plants may sprout from seeds or fragments.

Check your garden regularly for signs of onion grass and remove them promptly.

Bonus Tip

Do not compost or discard the dug-out onion grass in your garden, which can spread the seeds or fragments. Instead, put them in a sealed bag and dispose of them in the trash.

How To Spray Onion Grass With Herbicides?

Spraying onion grass with herbicides is an alternative to removing it if you have a large area infested with onion grass or cannot manually dig out the plants.

However, herbicides may not be effective against mature plants or dormant bulbs and may harm other desirable plants if not applied carefully.

Herbicides for Onion Grass

Some of the herbicides that are effective against onion grass are listed below.

Option #1: Glyphosate

Glyphosate is a non-selective herbicide that kills any plant it contacts.

It can be used before planting or harvesting but not during the crop’s growing season.

Glyphosate can serve as a targeted treatment for specific onion grass plants, ensuring not to spray neighboring plants.

Option #2: 2,4-D

2,4-D is a selective herbicide that kills broadleaf weeds but not grasses.

It can be used in lawns or pastures where onion grass is mixed with other grasses, but not in vegetable or flower gardens.

Option #3: Paraquat

Paraquat is a selective herbicide that kills onion grass in spring when the plants are actively growing.

It can be used in vegetable or flower gardens before planting or after harvesting but not during the crop’s growing season.

Option #4: Imazaquin

Imazaquin is a selective herbicide specifically designed to target and eliminate onion grass during autumn when the plants are transitioning into dormancy.

It is suitable for application in vegetable or flower gardens before planting or after harvesting.

However, it should not be used while the crops are actively growing.

How To Prevent Onion Grass From Growing Back?

Preventing onion grass from growing back is important to maintain a healthy and beautiful garden.

Here are some tips to prevent onion grass from growing back:

  • Keep your lawn thick and healthy. A dense lawn can prevent onion grass seeds from germinating and competing with the grass. Mow regularly and fertilize appropriately.
  • Apply mulch to your flower beds. Mulch can suppress onion grass seeds and prevent them from getting light and moisture. Use organic mulch, such as wood chips, straw, or leaves, and apply a 2 to 3-inch (5-7.5 cm) layer around your plants.
  • Plant competitive plants. Some plants can outcompete onion grass and reduce its growth. For example, you can plant clover, mint, or thyme in your lawn or garden. These plants can also attract beneficial insects and improve soil quality.
  • Monitor your garden regularly. Check your garden for any signs of onion grass and remove it promptly. You can use any of the abovementioned methods, such as digging, spraying, or boiling water. Do not let onion grass flower or seed, which will increase its spread.


Onion grass is a pesky weed that can grow in lawns, flower beds, and pastures.

It has a strong onion or garlic smell and taste and can be hard to eliminate.

However, with the methods we have shared in this article, you can identify, dig out, spray, and prevent onion grass from growing back.

Following these steps, you can enjoy your garden without any onion grass.

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