Rocky,

I would check into a weed burner if the plants are at the water line. I always get a lot of maple seedlings at the edge of my stone and spend several days each season pulling them out. If you have never seen a burner , take a look at the following links;

http://www.flameengineering.com/Flame_Weeding.html

And here is a DIY version if you're a handyman;

http://www.agronomy.ucdavis.edu/LTRAS/itech/flame.html

Chip