Canna glauca aka Louisiana Canna

Canna glauca grows in wetlands and lives for years. It belongs to the canna family, Cannaceae. People call it water canna or Louisiana canna. Its native range starts in South Carolina and spans tropical America. It reaches south to Argentina, Uruguay, and Paraguay. Wild plants grow by marshes, swamps, ponds, and wet ditches. Thick rhizomes, or creeping stems, form upright clumps.

Garden plants grow 4–6 feet (1.2–1.83 metres) tall. Some stay near 2 feet (0.61 metres). Clumps spread 2–3 feet (0.61–0.91 metres) wide. They grow fast, and seedlings may bloom in their first year. Narrow, blue-green leaves clasp the main stems. Leaves reach about 1.5 feet (0.46 metres) long. Their paddle shape gives the plant a small banana-like look. The leaves add interest even without blooms. Strong winds can tear the broad leaf blades.

Pale yellow flowers grow in groups at the stem tips. They bloom through summer into early fall. Missouri Botanical Garden lists July to September as bloom time. The parts that look like petals are modified stamens. Green, prickly seed cases called capsules follow the blooms. Each has three sections. Butterflies visit, and Brazilian skipper larvae feed on the plant. Groups suit pond edges, bogs, and rain gardens. Plants also suit beds, borders, and large pots.

Give water canna sun or part shade, not full shade. It grows best in rich soil that stays moist. It accepts sand, loam, or clay across a broad pH range. In summer, it can grow in shallow water. The water may stand still or move slowly. Move plants into water in stages. Even so, wet soil that drains badly can rot rhizomes. Missouri Botanical Garden lists reliable hardiness in USDA zones 7–10. North Carolina State lists zone 11 too. Plant rhizomes once the risk of spring frost ends. Cut off spent blooms to help keep flowers coming. In cold areas, lift rhizomes after frost kills the leaves. Keep them cool and dry, where they will not freeze.

Japanese beetles and leaf-rolling caterpillars can harm leaves. So can slugs and snails. Slugs may cause great harm to fresh spring growth. Diseases include aster yellows, leaf spots, rust, and bacterial blight. People have dug the roots for starch to eat. Cooks can use young tubers, though they stay fibrous. Claims that the fruit is edible lack clear supporting detail. Plants For A Future and Useful Tropical Plants list no known hazards. This does not prove safety for every use or animal.