Water Caltrop
Exotic Aquatic Invasive Species

The Return of the Non-Native

Water Caltrop (Trapa bicornis),a.k.a. Water chestnut, Buffalo nut, Bat nut, Devil pod, Ling nut, Singhara, or Pani-phal, has claimed the biggest prize in our watershed, Lake Accotink itself.

November 6, 2022:
Despite the removal efforts last year, Water Caltrop returned to Lake Accotink in abundance in 2022. The Park Authority organized a series of workdays from August through November, to attempt eradication. We will know next year how successful the effort may have been.

The largest concentrations of Water Caltrop were back among the islands of the lake in areas too shallow to access by watercraft. Working in such places involves arduous toil in quagmires of astoundingly deep and sticky mud. Disposal is by dragging the heavy tubs to the highest driest accessible point nearby and leaving the water caltrop in piles to compost.

Water caltrop forms thick floating mats that can expand exponentially, shading out native submerged aquatic vegetation, causing declines in dissolved oxygen, and interfering with boating.

USGS map of Trapa bicornis locations Select "Records" tab for text details of locations.
USGS Trapa bicornis description
Fairfax County Water Caltrops page
2021 Water Caltrop Report


Volunteers toil in the Lake Accotink mud to remove Water Caltrop

The pretty poison of Water Caltrop in Lake Accotink