I have removed one of my flower beds returning it to lawn. In one corner I had some ground cover plumbago. I need tips on eradicating it. We thought we dug it up. But it is sprouting from any little piece of root that was left. I tried round up a couple of weeks ago, it is still or newly sprouting I don't know which. My husband is inclined to take the tiller to the area before he can plant grass seed. I am concerned if we chop these into little pieces we will just multiply them.

So how do I kill them so I can plant grass? Should I try to solarize the area first before I plant grass? just dig out as many as I can and plant the grass seed anyway?