I am just in the process of getting rid of an invasive plant. How large an area is it? Are you willing to forgo planting anything else for the rest of the season? If you are, then let the plants come up a bit, then cover the area with black plastic to exclude light. Leave it on for the rest of the season. Not very nice to look at (especially when you consider you could have a nice flower bed there instead) but it works.

Evening, I know injecting glyphosate in some plant works very well. Open a hole in the stem with an ice pick etc. Inject probably a 1-3% solution into the opened hole. Saves all the systemic BS. You could add some 2-4 D to the glyphosate and see what happens.
This is more enviro friendly than spraying the whole area.
Gets to the "root" of the problem so to speak. I'm sorry, had to do it! Dave