Q: How the hell do I get rid of onion grass? We recently laid some turf and in between spreading the topsoil and laying our lovely new Sir Walter, we became infested with the stuff. We tried glyphosate about five days before putting down the turf, but it didn't really work. The lawn has been down now about three weeks. Any suggestions? Chris, Nudgee.
A: ‘Onion grass’, eh!! You are probably referring to Onion Weed (Nothoscordum gracile). You certainly have a problem.
Onion weed is very difficult to get rid of. It CAN be done, but it requires patience and tenacity. How keen are you?
Glyphosate is a systemic weed killer, but its action is confined to that first set of ‘bulbs’ in plants that have that type of root structure. Your initial spray of glyphosate would have killed the growth of onion weed that was already above ground and the bulbs they were growing from, but it would NOT have affected the ‘bulbils’ (small bulbs) that had already formed underground as ‘off shoots’ from the original bulb. These bulbils have matured and are now causing you your present problem. Unfortunately these in turn would have produced many more little bulbils of their own, which will also grow up, and give you that proverbial headache.
Constant, repeated sprays of glyphosate will eventually get rid of the problem…BUT you will kill your turf in the process. How keen are you? You could use a gadget that one of my gardeners at Roma Street Parkland has developed…a set of BBQ ‘prongs’ with absorbent sponges attached to it. (Refer photographs). Dip the tip of the prongs into a solution of glyphosate, squeeze the blades of the prongs together to get rid of excess solution and then ‘wipe’ each blade of onion grass with it. This will be a long and laborious process, which will need to be repeated as and when the blades of onion grass pop up. It will do the job for you eventually and will save your turf.
Forking out the onion grass is never successful, as one invariably leaves many of the little bulbils in the soil. They break off from the mother plant very easily.
The best and quickest method of control is to square off the section of turf with the onion weed, and remove the turf AND soil to a depth of 100mm, and dispose of this. You will, of course, lose that section of turf and will need to refill the hole with good soil and lay that bit of turf again.
