Cabomba caroliniana aka Carolina Water Shield

Cabomba caroliniana is a water plant that lives for years. It belongs to the Cabombaceae family. Its common names include Carolina fanwort and Carolina watershield. It is native to central and eastern North America. That range reaches into northeastern Mexico. It is also native from Brazil to central Argentina. Kew places it in the subtropical climate zone. It is not native to Britain or Ireland.

Most of the plant grows below the water's surface. Its stems branch and reach about 6 feet (1.83 metres) long. The listed garden height is just 0.26 feet (0.08 metres). This is not the length of the stems below water. Its listed spread reaches about 3 feet (0.91 metres). Bright green leaves grow in pairs along the stems. The leaves in each pair sit opposite each other. Each fan-shaped leaf splits into many fine, threadlike parts. These give the leaves a soft look, like feathers. A few small leaves float near the branch tips. These leaves are narrow and oblong, with a peltate attachment. This means the stalk joins the leaf away from its edge. They rest on the water like tiny water-lily leaves.

White flowers bloom from May through September. They add interest above the finely cut green leaves. Gardeners grow this plant in water gardens and large aquariums. The leaves give it much of its appeal there. The plant takes up nutrients from the water around it. This can help curb algae and keep the water clear.

Grow it below water in full sun. Plants can root in mud or float free. Pots or other containers can hold them at the pond bottom. Loose cuttings and stem pieces can float in water too. Missouri Botanical Garden lists it for USDA zones 6–10. It is easy to grow, but check its spread often. Clip or remove stems to keep plant numbers in check. This task is easier in small water gardens than large ponds. Avoid large ponds, where its spread is harder to control.

Missouri Botanical Garden reports no serious insect or disease problems. Fast spread is the main concern for gardeners. In Britain, the RHS calls it an invasive non-native species. UK rules ban planting it or letting it enter the wild. They also ban its sale. Plants already there need control. Its worth as a garden plant does not remove that risk. The supplied sources give no guidance on whether it is safe to eat or toxic.