I am in need of some advice for planting some small greenery in and around my waterfalls (2 of them) in my pond. They need to be a fairly low grower, as the native watercress I like to plant (and that does so well) overgrows the falls by summer. I'm not concerned about flowering types, I would just like to add to the 'natural' look of it and I'm sure the critters in and around the pond would like them, too. I am in Indiana, BTW. I love the arrowhead plants, too, but the height always becomes an issue eventually. Thanks in advance for your input!