Water Hyssop threads itself through the wet margins of the coastal South, from southeastern Virginia across Florida and on to Texas, rooting wherever freshwater tidal marshes, muddy shores, or shallow stream edges offer a foothold. Its small, succulent leaves are evergreen and unscented — unlike its lemon-fragrant cousin Bacopa caroliniana — and they stay tidy and green through the long growing season. The white flowers begin in spring and continue well into fall, offering a sustained, if understated, presence in the water garden or bog.

What gives this plant its ecological weight is what happens beneath it: the small, succulent leaves are the sole food source for larvae of the White Peacock butterfly (Anartia jatrophae), making it an irreplaceable link in the chain of a coastal pollinator garden. It spreads readily in moist soil or shallow water and will spill gracefully over the rim of a pot or hanging basket in frost-free gardens. Zones 8 through 11 are its comfort zone, where heat tolerance is strong but drought tolerance is essentially absent. Keep it consistently wet and it will take care of everything else.