Common Hornwort – sometimes called Rigid Hornwort – is a free-floating, submerged aquatic plant which is most often found in backwaters.
Shoots of up to 1m long are formed. Their brittle but stout stems have whorls of 4 to 12 dark green, coarse leaves. Flowers are inconspicuous.
The ideal habitat is eutrophic ponds, backwaters and ditches with muddy bottoms, and warm water temperatures throughout the summer.
Endangerment and Conservation Status
The Hornwort's prickly little fruits are distributed by waterfowl. Like many aquatic plants, reproduction is primarily vegetative. In late autumn, terminal buds are formed on the lateral shoots of the plant. They fall off the main plant and over-winter in the mud while the remaining plant dies off. The next year, the young shoots break into smaller pieces and grow into stand-alone plants.
Common Hornwort is not anchored by roots, but is instead free-floating in the water.