June 2011 Trapa natans

WHAT IS IT? A floating or anchored aquatic annual Native to temperate zones of , Asia and north Africa Used in fish ponds, farm dams and water features Spiny fruit is high in fat and carbohydrates and was one of the first European domesticated for food Also known as: Jesuit , bull nut, wassernuss, waternoot, leng gok, singhara and European water chestnut Trapa natans. John M. Randall, The Nature Conservancy, Bugwood.org.

WHY IS IT A PROBLEM? The sharp spiny fruit are a hazard for humans and animals Forms impenetrable mats over wide expanses of water, which exclude native aquatic flora and fauna Lowers light levels consequently affecting the water temperature Infestation. LJ Mehrhoff, Univ Spiny fruit. L.J. Mehrhoff, Connecticut, Bugwood.org University of Connecticut, Inhibits boat navigation and other Bugwood.org. riparian recreational activities

What are State Alert Weeds? These are invasive weeds that are not known to be in South , or if present, occur in low numbers in a restricted area, and are still capable of being eradicated. An Alert Weed would pose a serious threat to the State’s primary industries, natural environments or human health if it became established here. All Alert Weeds are declared under the Natural Resources Management Act 2004: their transport and sale are prohibited (Sect. 175 and 177), plants must be destroyed (Sect. 182), and if found on your land their presence must be notified to NRM authorities (Sect. 180) – refer overleaf. DESCRIPTION An annual herb featuring a rosette of floating, fan-shaped leaves, each leaf having a slightly inflated stem. The roots and stems which are anchored in the soil below water level are fine and long. The small 4-petalled flower is white, and the fruit is a large nut with 4 sharp spines.

Flower. LJ Mehrhoff, Uni HOW IT SPREADS Connecticut, Bugwood.org Water caltrop reproduces by seed, each of which can produce 10-15 rosettes. Each rosette produces up to 15-20 seeds. The rosettes break away from the parent plant, become waterborne, and are transported to other areas. The seeds are also dispersed by animals and birds, and can remain viable for about 12 years.

HABITAT Found in stationary and slowly moving waterways in warm temperate zones.

Inflated stems. LJ Mehrhoff, Uni ORIGIN Connecticut, Bugwood.org Water caltrop is native to Eurasia and Africa, being found in temperate regions.

DISTRIBUTION IN AUSTRALIA Current: Not yet naturalised or known to be cultivated in Australia.

Potential: Water caltrop could naturalise in streams, dams and ponds in the southern parts of South Australia.

HOW IT GOT HERE Not known to be in Australia, but could be imported illegally as an alternative crop. DISTRIBUTION

Current distribution based on herbarium records WHAT CAN YOU DO? Potential distribution based on climate modelling Be on the alert for this plant using this Fact Sheet as a guide. If you see a suspicious plant that may be this State Alert Weed, please report it to your local Natural Resources Management (NRM) Board (contact details at www.nrm.sa.gov.au). For more information on weeds, including Alerts, contact your local NRM Board or visit either www.pir.sa.gov.au/biosecurity (phone 08 8303 9620) or www.weeds.org.au.

Disclaimer: This publication is provided for the purpose of disseminating information relating to scientific and technical matters. The Government of South Australia does not accept liability for any loss and/or damage, including financial loss, resulting from the reliance upon any information, advice or recommendations contained in this publication. The contents of this publication should not necessarily be taken to represent the views of the participating organisations