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Water Willow


Justicia Americana

This native aquatic plan, common throughout the 3RQ River Basins, is an important and valuable contributor to our river ecosystems.

Water-willow is an herbaceous perennial that is common along streams and rivers throughout the upper Ohio River Basin and across the eastern US. The common name comes from a resemblance of the leaves to willow leaves and the fact that it grows in water. Water-willow is one of the most productive emergent plants in shallow Appalachian rivers and streams.

Water-willow can spread vegetatively and from seeds, and forms extensive rhizomes that help stabilize shorelines and stream beds often forming dense colonies and spreading rapidly. The creeping rhizome allows J. americana to form large colonies on or near the shorelines of still or slow waters in lakes and rivers, and on rocky riffles and shoals in faster flowing rivers. Its rhizomes and roots provide important spawning sites for many fish species and habitat for invertebrates.

A member of the Acanthus family, which contains 250 Genera and about 2500 species of mostly tropical herbs, shrubs vines and epiphytes, J. americana is one of the few species in the family to live in a temperate region. Water-willow grows to 3 feet tall and has opposite leaves, long and narrowly tapered (up to inches 6 long and ½ inch wide) with smooth margins and a distinctive whitish midvein. Water-willow flowers from May through October. The flowers are on long stems originating from the base of the leaves. Flowers are 5-petaled orchid-like (3/4 inch diameter), white with purple/violet streaks on the lower petals. It is pollinated by bees and butterflies.

Submerged portions of all aquatic plants provide habitats for many micro and macro invertebrates. These invertebrates in turn are used as food by fish and other wildlife species (e.g. amphibians, reptiles, ducks, etc.). After aquatic plants die, their decomposition by bacteria and fungi provides food (called “detritus”) for many other aquatic invertebrates. Deer will browse the leaves while beaver, muskrat, and nutria will consume the rhizomes of water-willow. In agricultural streams, water-willow can be an effective mitigator of agricultural runoff by taking up excess nutrients.


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