Pontederia

These hardy, aquatic perennials are natives of North America. P. cordata, Pickerel Weed, has a creeping rhizome and erect, glossy, dark green leaves that are slightly heart-shaped. In the summer, racemes of violet-blue, funnel-shaped flowers are produced. This variety grows from 18 to 24 inches high. P. lanceolata has narrower leaves and grows 4 to 5 feet in height. It is a native of the southeastern U.S. and is therefore not as hardy as P. cordata. Its varieties Angustifolia and Alba are also not as hardy in northern water gardens. P. rotundifolia is a tropical variety with rounder leaves growing 2 to 4 inches long and 11/4 to 4 inches wide. It produces pale blue flowers. This vigorous-growing variety can be grown submerged or floating.

Pot Cultivation

These plants can be grown in water up to 18 inches deep. Plant them in 5-gallon containers or larger, in sun or partial shade. The less hardy species can be wintered in northern gardens by sinking them to the bottom of the pond where the rhizomes won't freeze.

Propagation

In the fall or spring, the rhizomes can be lifted, divided and replanted. The rotted portion from the previous year's growth should be removed and discarded before replanting and excessive roots should be trimmed away. The rhizome should be set in the pot so that the cut edge is near the edge of the container. This allows maximum growing room. Stolon cuttings may also be taken in the summer or fresh seeds may be collected in late summer and sown.