Trapa bicornis

Overview

Appearance

Trapa spp. are rooted, floating plants that invade shallow to deep, fresh water habitats in the northeastern United States. They can grow in 12-15 ft. (3.6-4.6 m) of water and form dense, floating mats, often three layers deep.

Foliage

Leaves on the surface of the water are alternate, triangular in shape, strongly toothed and connected to the stem by an inflated petiole. Submerged leaves are feathery and either opposite or alternate.

Flowers

Small, four-petaled flowers bloom from mid-summer to frost.

Fruit

Fruit is nut-like . T. natans fruit have two to four, 0.5 in. (1.3 cm) long, sharp, barbed spines. The spines can penetrate shoes. T. bicornis fruit has two curved horn-like spines.

Ecological Threat

Trapa spp. form dense, floating mats that restrict light availability, reduce the oxygen content, and displace other emergent and floating vegetation. These species can also limit boating, fishing, swimming and other recreational activities. Trapa spp. are native to Europe and Asia and was first observed in the United States in Massachusetts in the late 1800s.