Pulled out the mother of all onion weed plants this morning, and thought it demonstrated perfectly why onion weed can never be defeated! But I have had some mild success against the stuff – no victories, mind you – just the kind of successes where I can grow other things without onion weed ruining everything. My garden still has onion weed, and always will.
Viewed close up, it's obvious why onion weed always bounces back after you've dug it out of the ground. With all those little bulblets just waiting to drop off, no matter how careful you are about digging out the main bulb you'll leave behind at least one bulblet, if not a dozen or more.
This time I dug out a big clump of soil, then washed it to collect as many bulblets as possible, but I'm not kidding myself that this method means no more onion weed.
As well as dropping bulblets when you pull it out of the ground, onion weed has a 'slow-release' way of sprouting its bulblets, too, that makes it a weed you just have to admire for its adaptation and 'survivor' skills.
Imagine you have lots of onion weed bulbs underground in a garden bed. At any given moment, only a fraction of the bulbs will sprout and shows grassy leaves above-ground. The rest stay put underground, doing nothing for the meantime. They'll wait till another time a few days, weeks or even months later, to sprout. So, even if you eradicate all the onion weed you can see, more will come up later from the 'sleeping' bulbs.
Herbicides such as Roundup can kill onion weed, but this stuff isn't remotely organic and it's also easy to spill a deadly drop of it on a treasured nearby plant while you're trying to apply it to the onion weed. And besides, the Roundup only kills the onion weed above ground. All the 'sleeping' bulbs underground will come up later on, anyway.
Black plastic covering the soil is nasty even if it's crudely effective. I think it's nasty because it 'cooks' every living thing under it, especially during summer. Healthy soils are meant to be full of air, to help plant roots breathe. Plastic smothers the soil and deprives it of air. It also heats the soil and can kill worms and lots of other beneficial micro-organisms, especially on a hot summer's day here in Sydney. And it's not porous, so it prevents moisture getting down into the soil, too, turning the soil bone dry. To my mind, covering soil with black plastic is bad all-round, and much worse than herbicide as a weed control.
I just use good old garden mulch (in my case sugar cane mulch), and pull out the onion weeds as I see them. Instead of using a two-pronged hand garden fork to pull out onion weed, wherever possible I just dig up a whole clump of soil around the weed, then fish out the weed and as many bulblets as possible, as per my photos at the top of this blog.
Sometimes this method isn't possible when weeds and wanted plants are all crowded in together. Sometimes I just break the onion weed leaves off at ground level, just to tidy up the look of the area.
In the end the main thing is to accept that you'll never get rid of onion weed completely. The best you can manage is to give it a hard time whenever the opportunity presents itself. But deep down, I don't hate this plant. I almost admire it sometimes, but not quite.