Garlic mustard (Alliaria petiolata) is a biennual herb that smells strongly of garlic. The herb was introduced to the United States by European settlers who used it in cooking and for medicinal purposes. The plant has quickly spread from Canada to the Carolinas and as far west as Washington state. It is considered a serious threat to native plant life and woodlands. Each plant can produce hundreds of tiny seeds from small white flower production. Eradication is gained through hand control, mowing, shearing, fire and herbicides.
Pull garlic mustard by hand prior to flower production in the spring. Promptly dispose of hand-pulled plants in a plastic garbage bag. Garlic mustard can be cut at ground level using a lawn mower or garden shears and the top growth removed on 1-year-old plants to help gain control. Garlic mustard seeds are viable for five years, so annual pulling and cutting will be required prior to the plants' seed production to gain control.
Burn areas of large infestation in the spring and fall. Check with local fire authorities to make sure that field burning in the area is permitted for control of garlic mustard plants. Many areas ban field burning. Burning will kill first year plants, but not the seeds. so germination will still continue and control must be maintained for up to five years to be effective. A combination of annual burning, hand-pulling and cutting with a lawn mower or shears can be quite effective over a three- to five-year span.
Apply the herbicide glyphosate to garlic mustard foliage. Care is required when using glyphosate because it will kill native plant life, too. Applications of the herbicide are most effective in the early spring and late fall. Glyphosate should be applied early enough in the season or late enough in the season that native plants are dormant. Target only the mustard garlic plants and do not allow excessive dripping to occur on the plants' foliage, which will contaminate other areas and plants with the herbicide. A solution of 1 to 2 percent glyphosate mixed with water in a handheld garden pump sprayer is ideal. Follow the directions on the brand of glyphosate that you purchase for application. Each brand will have directions for different concentrations.