Oh My I'd love to have those flowers
right Now,, I have No idea how to rid your self of them other than pulling them out like you have been, you'd have to get the bulbs and all.
I just looked them up and from what I understand they donot like really warm weather. ( don't know if that helps you or not?
I know this sounds like a lot of work But you'd have to get all the bulbs out of the area,, OR move your veggie garden to another place. Is this the first year for your veggie garden in that area?