What Is Onion Grass?

Identification

• Onion grass is easily differentiated from garlic grass by its leaves, which are flat and solid, unlike wild garlic leaves, which are hollow. Onion grass leaves attach only to the top of the bulb. Onion grass smells strongly of onion when it's cut. The herb produces flowers in late spring atop stems that can grow to 3 feet tall. The flowers of wild onion become bulblets, which drop to the ground to germinate the following spring.

Range

• This perennial herb grows in much of the United States, especially the northeast and upper Midwest. Dry, arid climates do not usually see this herb, but it may appear in agricultural areas. Wild onion is more common in lawns than wheat fields or pastureland; however, its presence in pastureland poses a danger to cattle that can die from poisoning if they eat too much of it.

Prevention

• In the home landscape, prevent wild onion infestation by maintaining a healthy lawn with tall, thick turf. As with any weed, sparse turf leads to proliferation of onion grass because there's no healthy competitive grass to crowd it out. Letting your grass grow taller and keeping it mowed to 3 inches will shade the soil and prevent weeds from gaining access to sunlight.

Control

• Should you choose to control wild onion with an herbicide, the Michigan State University Extension office recommends a post-emergent, broadleaf herbicide. Regular mowing may also prevent the herb from setting and dropping seed, reducing its numbers the following season. Hand digging wild onion with a thin trowel may be the most effective control method when there are only a few plants in the yard.