Get rid of wild onions by regularly mowing at the lowest suitable setting, digging up persistent plants and treating the area with a broadleaf herbicide in the late fall. The process takes an entire growing season.
- Mow the lawn at the lowest setting
Start mowing the affected area in the early spring at the lowest setting possible that does not damage the lawn. Low mowing weakens the wild onion plants and keeps them from going to seed. Continue mowing regularly at a low setting throughout the growing season.
- Dig up persistent onion plants
Watch for the distinctive smooth, hollow shoots of the wild onion weeds. When wild onion plants grow higher than the surrounding yard, dig them out with a narrow trowel. Work to remove all of the bulbs underground in the area around the plant.
- Apply a herbicide near the end of the growing season
In early November or later in warm climates, apply a post-emergent, broadleaf herbicide to the lawn according to the manufacturer's instructions. Mow the lawn right before the application for best results. After applying the herbicide, do not mow again for at least two weeks.
- Reapply the herbicide
After two weeks, mow the affected area, and treat it a second time with the herbicide.