Virginia Invasive Species

Early Detection Invasive Plant Species of Virginia

Two-horned Trapa

(Trapa bispinosa)

two-horned water chestnut flower, fruit, and leaves

Two-horned water chestnut flower, fruit, and leaves. Photos by Blythe Merritt.

What's the harm?

Two-horned trapa readily invades freshwater habitats such as ponds, lakes, and slow-moving streams. Like the better known Eurasian water chestnut (Trapa natans), two-horned trapa can form dense mats on the surface of a waterbody, choke out native submerged aquatic vegetation (SAVs) and other plant species, and reduce the navigability of waterways.

two-horned trapa infestation

What is it?

An annual aquatic plant species that roots in shallow freshwater habitats such as ponds, lakes, and slow-moving streams.

 

Where's it from?

Two-horned trapa is native to Taiwan. 

 

How did it get here?

Unknown. It may have been introduced intentionally for horticultural use, by edible plant enthusiasts, or by accident. The earliest known population in Virginia was discovered in 2014. Herbarium specimens discovered to be mislabeled date to 1999.

two-horned trapa seed pod

 

Where is it now?

At present, in North America two-horned trapa is it is only found in Virginia at over 70 sites in four Virginia counties: Fairfax, Prince William, Loudoun, and Fauquier. Waterfowl are known to move the seeds to new habitats.

[map coming soon]

 

What's being done?

Removal has begun at several sites. Funding is being sought to conduct further control. Federal funding has been earmarked for surveys, mapping, and outreach. A steering committee--comprised of local, state, and federal agencies, and citizen groups--has formed to coordinate activity aimed at the eradication of two-horned trapa in Virginia.

 

How do I report a sighting of these species?

You can choose from several ways to report sightings of an invasive species here >> 

 

How can I learn more?

See our fact sheet here >>

See more information, photos, and an interactive map here >>