According to my weed book, your only option is to dig and dispose of each and every one -

A narrow but deep-bladed transplanting or rootball spade is the best weapon against wild garlic or onions. Its blade is deep enough to reach under the bulbs, and its handle is strong enough to lever out the clump. Dig close to the clump, with the blade at a very slight angle, then lift. With your hands, pick out every bulb from the soil, even the tiny ones. Dispose of them in the trash, not on the compost pile.

A pointed shovel or spade is as effective as a transplanting spade, but removes a bigger bite of soil and surrounding plants.

OR you can "throw in the trowel", and harvest them for culinary and/or medicinal use. The bulbs, green tops, and even the flowers are tasty in a variety of dishes.

It's also great for treatment of sore throats by steeping it in boiling water and gargling. So many good things about it. :)

Brenda

It sounds like you have Allium triquetrum, which is a problem in my garden too. It had taken over a large area around a hydrangea, and I was able to completely eliminate it there by digging it out and then laying cardboard down.

In the rest of the garden, I pull it out every year and have just resigned myself to the fact that it will still come up. I even let some of them bloom because they are pretty, in moderate quantities. After all, some bulb companies actually sell them!

Here is a link that might be useful: Allium triquetrum -10 bulbs for 4 dollars!

Thank you both for the information. susanc you have indeed identified the plant that plagues me. I'll try the digging and cardboard solution.

Youreit, I will follow your advice regarding digging them up.

Robert Smaus wrote about these frustrating bulbs in his book, I think it was called Twelve Months in the LA Garden or something like that. As many of you know, he was the LA Times gardening expert for many years. The article was hilarious, and l could certainly relate. I've had these pests for over 10 years now, and I've tried everything, from spraying poison (does not work on them) to covering them with concrete blocks (they grow under and around them) to digging up each and every one (you have to get each tiny bulb, or else they will come up again. And each major bulb has about 50 tiny babies attached.)
Robert Smaus recommends digging as much soil around, and under, each plant, and throwing it away, dirt and all, and keep your garbage bag right there so that none escape. Otherwise, to get rid of them completely? Move!
Good Luck,
Suzie

Please post a photo. It may not be an onion, and it may not even be a California native ("wild"). There is an invasive bulb from South America called Nothoscordum inodorum that has become a problem in California. Has a strong, sweet fragrance. It produces lots of small bulblets each year, and must be dug out very carefully and discarded safely (don't throw it over the fence).

Here is a link that might be useful: Nothoscordum inodorum

Arvind, please reread my description, susanc's response with a photo of exactly what I have, and my response to her. They have a stinky onion smell. The bulblets are white not brownish. What sort of gardener would ever toss anything over any fence?

Sorry, didn't mean to cast aspersions. I have not had any experience with A. triquetrum (of Mediterranean origin), and I must say I am grateful for that. :)