Onion weed is a proclaimed noxious weed for most of Australia, it is a perennial weed with thin green strappy leaves growing from a mainly white bulb which gives off an onion smell when crushed. Flowers grow at the top of a long stalk and are mainly white.
The conditions at the moment are absolutely perfect for seeding, which usually takes place in summer and autumn and are spread mostly by wind blowing the seeds into new areas. Onion weed also develops small bulblets attached to the parent bulb. These sprout after the main parent bulb has died making eradicating this weed a pain.
Removing Onion Weed
Eradicating onion weed starts with removing as many of the plants as possible. Do not try to pull the plant out of the ground, or shake excess dirt back off into the hole or compost. The small bulblets tend to pull away from the mother plant when pulled, which leaves more bulbs in the ground that will rapidly grow. If possible, dig the weed-clump out of the ground with a spade or a trowel, and throw the entire clump away.
The next step to total eradication of onion weed is to treat the area with either a non-selective herbicide (like Roundup) or even boiling water. Both options will kill any plant it touches, so be wary of surrounding plants. You’ll need to use a paintbrush or a weed-wand which has a specially developed valve on the brush that prevents any leaking. It requires a dilute glyphosate solution to control and is a good way to give you a bit more control.
It can help to add a slight amount of household detergent – about the same rate as the herbicide concentrate amount – this helps the herbicide to stick to the waxy leaf and penetrate to do its work. Keep an eye out on your lawn, and repeat the process if any new onion weeds begin to grow.
If you’re unable to treat the area, keep the plants trimmed near the ground if possible as this will prevent the onion weed from flowering and spreading to other parts of your lawn or garden through seeds.