The Q&A Archives: how to kill onions

Question: Is there a way to specifically target and kill weed onions in my lawn?

Answer: Wild garlic (Allium vineale) and wild onion (Allium canadense) are winter perennials. They emerge in late fall from underground bulbs and grow through the winter and spring. The underground bulbs can persist in the soil for several years. While both have thin, green, waxy leaves, those of wild garlic are round and hollow, while those of wild onion are flat and solid.

They can be difficult to control. Here are some options:
With a small number of weeds, pulling, though difficult, is an option. It?s likely, however, that bulbs or bulblets will be left in the ground and new leaves will later re-emerge. For best results, dig them out, roots and all, with a thin trowel.

While mowing will not kill wild garlic or wild onions, regular mowing can weaken plants and prevent them from setting seed.

Unfortunately, there are no preemergence herbicides that will control wild onion or wild garlic. They must be treated with a postemergence herbicide, and persistence is the key. Plants will need to be sprayed more than once and for more than one season. One characteristic that makes control difficult is that both have a thin, glossy leaf to which herbicides don?t readily adhere. Adding a spreader-sticker to the spray solution will help it to adhere evenly. Be aware that some products have a spreader-sticker already added, so read the label completely before using the product. Unlike most weeds, mowing wild garlic or wild onion immediately before applying an herbicide may improve uptake. After application, do not mow for at least two weeks.

For best results, treat wild garlic and wild onion in November and again in March. However, be careful not to apply most weed killers onto centipedegrass or St. Augustinegrass during their spring greenup period. Inspect the lawn the next fall and spring and treat if necessary.

Recommended Herbicides: Imazaquin, the active ingredient in Image, will provide control for wild garlic and wild onion. This product should not be used on fescue and should not be applied to warm season turf while it is beginning to green in early spring.

Broadleaf herbicides containing 2, 4-D, such as Trimec or Bayer Advanced Southern Weed Killer for Lawns, will also provide control of wild garlic and wild onion with repeat applications. These products can be used safely on most turfgrasses but reduced rates are recommended when applying to St. Augustinegrass or Centipedegrass, and do not apply these herbicides during the spring greenup. Check the product label.

I've had good success in digging the wild onions out of my yard. It takes patience and persistence, but it works.

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