Good idea for multiple reasons: equisetum (horsetail, snake grass, puzzlegrass) (grow zone grows so quickly and make even the newest newbie of a gardener feel accomplished and happy. equisetum can get out invasive and a container will control it.
Containers for poolside. Plants for Containers in the Sun. My favorite perennial for pots in the sun — sedums of all types. I also love grasses with trailing plants, the photo right being a stunning example of combination.