Give the Tea Cups a lot of water, mine are growing in shallow water. They send out a lot of little runners which send up new plants. They really multiply fast (maybe not as fast as Bermuda Grass, LOL). I have a few nightmare grasses but not near the gardens. The seeds are carried around by animals and surface water. The water movement I'm controlling with swales. The weeding is still a permanent job. But I agree, cardboard is the best to combat grasses like the Bermuda Grass you describe. I tried some of what we call "weed mat", a tightly woven plastic cloth which allows water through but not weeds. After a number of years roots manage to grow through it and then it's impossible to remove. At least cardboard breaks right down.
