Fairfax County is working in collaboration with the US Geological Survey (USGS), Northern Virginia Soil and Water Conservation District (NVSWCD), regional jurisdictions and private landowners toward control and eradication of the non-native invasive aquatic weed, trapa (commonly known as water chestnut or caltrops). All trapa quickly can become a nuisance to our ponds and rivers, but since 2014 Trapa bispinosa (two-horned trapa) has been an emerging threat that appears to be spreading within and among many stormwater ponds and other waterbodies in Fairfax County. More recently, observed populations have been invading other areas of Northern Virginia and have doubled in some years since 2018. The good news is as of 2021 this plant is known to be in fewer than 100 local water bodies. We are confident this partnership and platform will be a valuable component of a fully coordinated effort to achieve eradication of trapa.
Coordination among interested parties requires communication and we hope this site provides a platform where you can report a possible sighting (USGS - Sighting Reporting Form), ask questions and seek advice (Northern Virginia Soil and Water Conservation District), request control help from local environmental groups, and share experiences among social media groups. If you think you have trapa in your pond, we strongly urge you to follow these steps:
Allowing T. bispinosa to proliferate in your pond will create an abundant seed bank, which can in turn lead to this plant spreading to other water bodies. These seeds may transport by streams, creeks and flooding events that connect water bodies; but the most common vector is seed transport by waterfowl. The ‘horns’ of the seed pod become lodged for travel on a bird, leading to an unpredictable spread of this plant. If you have T. bispinosa in your pond, the problem may not be as isolated as you’d reasonably expect. If you have waterfowl visit your water body, you may one day have T. bispinosa.
