How to Get Rid of Wild Onions from Your Garden

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Wild onion, or onion grass, is related to the garden-grown variety used in meal preparation. Wild onions are ed­ible; however, the species is too invasive to cultivate. It is important to know how to get rid of wild onions in gardens and lawns, once discovered. Understanding how they grow and spread helps when handling the plants. Herbicides are effective but require a specific type and method of application. More environmentally-friendly methods may be just as effective. Regardless of the manner used, removing wild onions requires persistence.

How Wild Onions Grow and Spread

Lawn care experts verify that onion grass is a perennial, living for several seasons. Roots and bulbs grow throughout the winter months, sprouting new shoots in early spring. The vegetation produces flowers that generate bulblets. The bulblets drop and take root to form larger and thicker patches. During hotter months, it becomes dormant until fall when the onion sprouts and blooms again.

Should a bulb or root system become separated from the patch, this plant material will produce a new wild onion. Bulbs and bulblets can remain buried for years waiting for the right environment to sprout. Understanding the propagation processes will direct how to get rid of wild onions.

Physical Removal of Plant Material

Two factors determine success when physically removing wild onions by mowing, cutting, pulling, or digging. First, the process requires repetitions over multiple seasons. Second, eradication of plant material is essential to prevent regrowth.

Mowing an Onion-infested Lawn

Well-maintained lawns are at lower risk for infestations, but few homeowners enjoy ideal conditions. Thin, weak root systems and bare patches allow weeds to push through. Mowing consistently and correctly not only helps encourage healthy grass but also discourages weed seed propagation. Mowing established grass to no shorter than 3.5 inches helps keep a strong root system intact. Regular mowing ensures cutting the grass blades across their broadest width instead of cutting through their stems. This method keeps the lawn lush.

When considering how to get rid of wild onions by mowing, the objective is preventing bulblet formation. This prevention controls spreading into nearby gardens and flowerbeds. However, even years of repeated mowings will not kill the established bulbs. If the grassroots cannot choke out the bulbs, the onions will require further eradication efforts.

Pulling, Chopping, and Digging Wild Onion Patches

The lawn care experts explain the pros and cons of manually removing onion plants. Pulling is not advised, as it easily leaves pieces of roots and bulbs in the soil. Remaining onion sets will regrow new shoots and bulblets. Loosened and scattered soil may spread the infestation to a larger area.

The Pulling Method

If the pulling method is employed, it is best to pre-moisten the soil. The area should be soaked with 1.5 to 2 inches of water beforehand. Knowing how to get rid of wild onions by pulling requires understanding one precaution. The onion matter contaminates the soil surrounding the plant: it must not be shaken, mulched, or composted. Disposal of pulled clumps of wild onions and the surrounding soil is necessary.

The Chopping Method

Similar to mowing, chopping manages the onion’s spread by preventing the formation of bulblets. However, chopping as close to the soil surface as possible is more effective than mowing. Repeatedly and drastically trimming vegetation inhibits photosynthesis, so the plant is unable to produce energy. Combined with lack of bulblet propagation, this method improves the eradication process.

The Digging Method

The best manual removal method is to dig around and remove the entire clump. As when pulling onions, discarding the entire soil clump is essential. Diligent plant removal and propagation prevention are how to get rid of wild onions.

Chemical Removal of Wild Onion Plants

Herbicides are considered an ultimate method of weed control. Unfortunately, wild onions can survive herbicide applications not tailored to kill them. First, the herbicide must be of the correct type and chemical makeup. Second, the wild onion’s leaf structure necessitates modification for chemicals to adhere to or penetrate the plant. Employing the proper type and application method will improve the chance of herbicidal eradication success.

Choosing Effective Active Ingredients

Pre-emergent herbicides are not suitable for killing wild onions, only post-emergent types work. According to Clemson University’s Extension office, one ingredient useful in killing wild onions is Imazaquin. Another effective herbicide contains a mixture of the ingredients 2, 4-D, dicamba and mecoprop (known as MCPP) which works well but requires repeat applications.

The ingredient metsulfuron is quite effective at controlling wild onions. Finally, glyphosate is a nonselective herbicide quite effective in controlling wild onion although it will kill any vegetation it settles on. Therefore, desirable plants require shielding, such as with cardboard, during application.

Less Toxic Ingredients

For less toxic alternatives horticultural vinegar and boiling water both work. Horticultural vinegar has four to six times the acidity of household vinegar, acid being the active ingredient. Vinegar and boiling water are nonselective, so either will kill any vegetation they contact. As for how to get rid of wild onions by applying herbicides, repetition is key.

Tips for Successful Chemical Removal

  • Clemson University also offers that wild onion should be treated in November and again in late February or early March. This schedule inhibits the production of new bulbs.
  • The lawn requires inspection each spring and fall for new growth.
  • Herbicides should be sprayed a calm day to prevent broadcast.
  • Mow or manually damage the surface of the foliage, so it better absorbs the chemicals.
  • Addition of a non-ionic surfactant increases the herbicide’s ability to adhere.
  • Spray herbicide on the wild onions monthly during its growing season, continuing for as many seasons as necessary.

In Conclusion

Eradicating wild onions can be frustrating and tedious for the most enthusiastic of gardeners. Manually removing the plants requires meticulous attention to discarding all contaminated soil. Herbicidal applications are typically toxic and harmful to desirable plantings. Most importantly, persistence is primarily how to get rid of wild onions. Trim, dig, and spray until inspection reveals a healthy, onion grass-free garden.

Jonathan E. Bass

Graduated from Middle Tennessee State University. I am currently a gardener. I have a small garden behind my house. I love it.

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