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Hemlock (Conium maculatum)

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Synonym(s): Poison hemlock, Spotted hemlock


Introduction

  • Hemlock   Hemlock (Conium maculatum)  is a multistemmed annual or biennial noxious weed.
  • Found along roadsides or uncultivated areas, eg ditches, fields, etc, often in dense stands.
  • Fernlike leafy plant with clusters of small white flowers.
  • The stems have purple spots, especially near the base of the plant.
  • Can grow up to 6-10 feet tall.
  • All parts of the plant are toxic; the seeds contain the highest concentration of toxin.
  • Native to Europe and Asia, and naturalized in most of North America.
  • Also affects cattle, sheep, goats, pigs, poultry, elk and man.
  • No treatment available.
  • Ensure removal of the plant from pastures before seeds form to prevent spreading.
  • Most horses will avoid the plant unless grazing is particularly poor.

Toxicity

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Clinical signs

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Treatment

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Panter K E, Bunch T D & Keller R F (1988) Maternal and fetal toxicity of poison hemlock (Conium maculatum) in sheepAm J Vet Res 49, 281-283 PubMed.

Other sources of information

  • Knight A & Hall J (2004) The 10 Most Dangerous Plants for Horses. Equus 320, 71-81.
  • Knight A P & Walter R G (2001) A Guide to Plant Poisoning of Animals in North America. Teton New Media, Jackson, Wyoming.
  • Burrows G E & Tyrl R J (2001) Toxic Plants of North America. Iowa State University Press, Iowa.
  • Allison K (1999) A Guide to Plants Poisonous to Horses. J A Allen & Co Ltd. ISBN: 0851316980.
  • Cooper M R & Johnson A W (1998) Poisonous Plants and Fungi - An Illustrated Guide. The Stationery Office. ISBN: 0112429815.
  • Allison K & Day C (1997) A Guide to Plants Poisonous to Horses. British Association of Holistic Nutrition and Medicine.

Organization(s)

  • Cornell University - Poisonous Plants Informational Database. Website: www.ansci.cornell.edu/plants.
  • Guide to Poisonous Plants. Website: www.southcampus.colostate.edu/poisonous_plants.
  • ToxicologyOnline.com. Website: www.toxonline.com.
  • Veterinary Poisons Information Service (VPIS), London Center, Medical Toxicology Unit, Avonley Road, London SE14 5ER, UK. Tel: +44 (0)20 7635 9195; Fax: +44 (0)20 7771 5309.
  • Veterinary Poisons Information Service (VPIS), Leeds Center, The General Infirmary, Great George Street, Leeds LS1 3EX, UK. Tel: +44 (0)113 245 0530; Fax: +44 (0)113 244 5849.

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