Wild onions can affect the taste of some of the plants in your garden, take up valuable space, produce an unpleasant odor and reproduce quickly. They are not easy to get rid of, but there are several types of herbicides that will interrupt their growth cycle, eventually eliminating them from an entire area and from your garden. It takes regular applications of herbicide as new growth from buried bulbs emerges.
Imazaquin works on broadleaf plants as well as certain grasses and other invasive plants such as morning glories, foxtail, nightshade and cocklebur. In most herbicide products it is mixed to work in conjunction with other chemicals, giving the entire mixture a broader range of effectiveness. According to the Extension Toxicology Network, a partnership between the U.S. Department of Agriculture and several universities, Imazaquin is "slightly toxic," causing irritation to the skin and eyes upon direct contact but without permanent damage. The toxicology network also found that it is non-toxic to wildlife, bees and aquatic animals when used in prescribed amounts.
Many of the herbicides that target broadleaf weeds without killing grass or desirable plants contain a combination of three chemicals, including 2 4-D, Dicamba and MCPP. While all of these chemicals generally work the same way, different broadleaf plants respond to each one differently. The combination will kill wild onions if the growth is above ground, but like other herbicides will not kill bulbs that haven't sprouted. The broadleaf herbicide combination of 2 4-D, Dicamba and MCPP is considered low in toxicity but is very irritating to the eyes and can cause itching and burning if it comes in direct contact with the skin.
A broad-spectrum herbicide, Glysophate will kill nearly every plant it comes in contact with, including wild onions. It can cause severe eye irritation, but according to Extension Toxicology Network, it was not found to cause skin irritation. It is also considered non-toxic to wildlife, bees, birds and aquatic animals, but other components commonly included in Glysophate-based herbicides are often toxic to fish.