Onion weed is a sedge-type weed and is a menace in lawns and gardenbeds right around Australia. It is one of the worst weeds that you can have take-hold in your yard as it is also one of the most difficult to get rid of. Onion weed is a proclaimed noxious weed for most of the country; for most of NSW and WA, and for all of Tas, SA and Vic.
Onion weed is a perennial 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. Seeds form in summer and autumn and are spread mostly by wind blowing the seeds into new areas. It has a ‘slow-release’ way of sprouting its bulblets, making it a weed you just have to admire for its adaption and ‘survivor’ skills. Onionweed’s thin, waxy leaves also make it difficult for herbicides to stick to the leaves, and even if it does, the wax makes it difficult for the herbicide to affect the plant.
Eradicating onionweed starts with removing any 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 onionweed is to treat the area with either a non-selective herbicide (like Roundup / Glyphosate) 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 to carefully target the onion weed plants and avoid your lawn if possible. It can help to add a surfactant or a slight amount of household detergent – about the same rate as the herbicide concentrate amount – and when added to the mix 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 onionweeds 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 onionweed from flowering and spreading to other parts of your lawn or garden through seeds.
Hopefully this process will allow full eradication of onionweeds from your lawn and garden. Be patient, it can be a tedious exercise, but show no mercy, and don’t give up hope. It will be well worth it to be onion-weed-free in the long run. Lawncare doesn’t need to be difficult and simple hints from Lawn Solutions Australia and their network of member turf growers and Lawn Solutions Centres Australia-wide can help with products to keep your lawn in top condition this winter.