Photo by Leslie J. Mehrhoff, University of Connecticut, Bugwood.org

European Water Chestnut (Trapa natans) is a floating aquatic annual which is native to Europe, Asia, and tropical Africa. It was introduced to North America as a garden specimen. The plant can grow up to sixteen feet and forms thick mats. It causes damage to aquatic environments by shading out native plants, and decreasing the level of oxygen in water. The quickly spreading plant also makes boating, fishing, and swimming difficult because of the overgrowth of the plant’s vegetation in waterways.

The plant has leathery, glossy, triangular leaves (5 cm wide) that have toothed margins. The leaves form a radiating pattern or rosette that is up to 30 cm in diameter. The undersides of the leaves are covered with soft hairs. Spongy inflated bladders on the leaf stems help the plant float on the water’s surface. Below the waterline the plant has feathery leaves along its stalk. A distinctive trait of this plant is its woody nutlets with four sharp barbs which can get caught on recreational gear, clothing, or exposed flesh. They can also potentially be carried by wildlife. These nutlets can produce up to 20 new rosettes, which in turn can produce up to 20 new nutlets. The seed is viable for up to 12 years.

You Can Stop the Spread of Invasive Plants. Always Clean, Drain, and Dry Your Boat, Paddle Gear, and Footwear.

  • Clean all plant stems and fragments and mud from boats and trailers before leaving your lake or river and dispose of them in an aquatic invasive species disposal station if one is available.
  • Empty all water from your gear well before moving to a new body of water.
  • Dispose of leftover bait in the trash, not in the water.
  • Clean out waders and wading boots before moving to a new body of water.
  • Dry your boat and gear thoroughly between waterbodies by towel drying or drying in the sun for at least 5 days.

Report European Water Chestnut with http://www.nyimapinvasives.org/. You can help ADK (Adirondack Mountain Club) survey ponds and lakes for aquatic invasive species such as Yellow Floating Heart, European frog-bit and European Water Chestnut. For more information on the Backcountry Water Monitors Project and upcoming workshops and outings visit www.ADK.org.


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