in what grass are they growing?
They are growing in my island, which is mulch covered.
As with many weeds in this type of situation, Carol, you have two options. You can dig them up, or you can use an herbicide. The challenge with wild onions is that in addition to the green leaves you see, there are also little bulblets under the ground. So, while an herbicide might kill some of your wild onions, there are more, lurking, waiting to shoot up and taunt you. You might, therefore, find it more effective to dig them up, because then you can root around and get all the little bulblets, too. You'll probably find a thin trowel or one of those dandelion diggers helpful. If you can isolate the wild onions from other plants in your island, you can use a nonselective herbicide like glyphosate. Because the leaves are somewhat waxy, you might want to add a little dishwashing soap to act as a surfactant. Either way, expect to have to keep after them. Here is an article from the Clemson University Cooperative Extension Service that you may find helpful:
Thanks, Doug for your help. I have spent hours and hours digging the onions to get to the bulbet, and unfortunately, they came back doubled. I give up.
However with the wild garlic I put it in pots and they sprout a beautiful purple flower (they are blooming now in Ohio). Then if you cut them back after they are done blooming, they will bloom again. I have no trouble with them, but the onion, yikes. Wonder if you could smother them?
I doubt smothering would be very effective, Carol, but it would no doubt be satisfying.
Image for Nutsedge is labeled for onion control
Thanks, Walter, I'm going to try it!
I had a yard full, someone told me lime killed them, I put lime all over & the next year had NONE....also Lawn & Garden 20% vinegar sprayed on them if there aren't too many because it will kill anything it touches. This also kills dandelions..