Question:
How do I control onion grass in my lawn?Answer:
Wild onion (Allium canadense) and wild garlic (Allium vineale) are perennial weeds most noticeable in spring. These tough-to-kill clump-forming weeds grow quicker than the surrounding turf and have a distinctive onion smell. Foliage typically dies back by early summer and is not visible for the remainder of the growing season. Each clump is comprised of many small bulbs underground. These bulbs are the reason why this plant is so difficult to control.
Hand Pulling & Digging
Hand pulling is difficult because leaves will break off, leaving bulbs behind that can regrow. When digging, it is best to remove the clump and surrounding soil with a hand trowel or soil knife, then discard the plants, bulbs, and soil. This better insures all the small bulbs are removed. Any small bulb left behind will regrow. Follow behind with a bag of topsoil to fill in the holes and overseed if necessary. A healthy stand of turf can prevent these weeds from establishing, so proper mowing, watering, and fertilization practices can reduce future infestations.
Herbicides
Herbicides have a limited impact on plants. Most lawn herbicides will burn back the foliage, but it takes repeated and persistent applications to kill the bulb. Products that contain a mix of 2,4-D, MCPP, and dicamba are often easy for most homeowners to obtain and can kill the entire plant, though it takes several applications. Non-selective herbicides can be used, but should be applied as a spot treatment as it will also kill surrounding turf. Products that contain metsulfuron, sulfentrazone and metsulfuron, or sulfosulfuron are also somewhat effective. All herbicides will require multiple applications to fully kill the weed.
Herbicides are more effective if applied to damaged leaves. Mowing before application, or cutting and spraying, can improve the herbicide's efficacy.
Photo credits: Ohio State Weed Lab The Ohio State University, Bugwood.org