Although it might seem convenient to have onions growing in your yard, wild onion (Alium canadense), also called wild garlic, grows as a weed in many areas. This cousin to the onions people keep in their vegetable garden spreads across lawns and propagates readily by seed or by putting out new bulbs. Mowing or cutting them down is one chemical-free control option.
Timing to Control
Wild onion bears flowers in early summer. With their pink-and-white petals, these flowers are attractive, but go to seed if not cut. The seeds germinate and eventually grow into more onions. If your aim is to control the spread of wild onion, but you still want to enjoy the flowers, mow or cut them as soon as the flowers fade. If you have no interest in the flowers, mow or cut the plants as soon as the flower stalk appears.
Timing to Weaken
If wild onions grow densely in your lawn and your goal is slowing their spread, weaken the plants. When the weather forecast calls for a lengthy period of hot, dry weather, get ready to take action. At the start of hot temperatures, mow your lawn with your mower's height adjusted to the lowest setting. This weakens the plants by removing their energy-producing leaves and causing rapid moisture loss from the cut foliage. It also forces them to put more energy into repairing the damage than putting out daughter bulbs.
Small wild onion patches can be cut down with garden clippers any time of year. If your aim is to control their spread, cut them before they seed or during hot and dry weather. You can also rid your garden of unwanted small patches by digging up the clump of onions. Pulling the plants won't work as well as digging because the main bulb or numerous daughter bulbs of often left in the soil.
Accepting Wild Onions
If you don't mind the scent, wild onions make an attractive plant. If you use nonchemical methods to control their spread, harvest and eat the wild onions in your yard. The leaves can be chopped up and used like chives, while the bulb is used as you would shallots. Before using the bulb, remove the outer covering since it has a bitter flavor. If rabbits are a problem in your area, the scent of wild onions repels them.