Juncus, the common rush, grows as a bundle of slender, upright, deep green stems, more architecture than foliage. It stays evergreen and vertical year-round, which makes it a favorite thriller for containers and a clean accent at the water's edge.

This is a true wet-soil plant: pond margins, rain gardens, boggy corners, and pots with saucers kept full all suit it. Give it sun for the densest growth. Beyond trimming tired stems in spring, it needs almost nothing from you.