If its a bulb the only option is to keep digging it out,making sure you get all the tiny offsets out too. Some of the smaller alliums are incredibly invasive, but usually do flower in late spring, often white flowered.

Sounds very much like wild garlic. A real pest and all you can do is to keep removing them.

Thank you for your responses, I have just googled 'wild garlic' and I think you are right.

Its going to be a long job removing them all, they are over the lawn!

Kind Regards

Chrispee

I have this in my garden. The offset bulbs are very tiny....like little round pearls. They send up their shoots in the autumn and bloom very late, and the flower is small and white. All you can do is keep a watch on it, dig it out or Roundup it if clump sneaks past your guard. I just had to go through a whole border to try and deal with it once the frost cleared this spring. Got my fingers crossed that I'm not going to see too many of those little pointy green shoots poking through.