Poison Hemlock

Latin Name: Conium maculatum

Identifying Characteristics:

  • Low growing rosette first year of lifecycle
  • 3-8 ft tall second year of lifecycle
  • Alternate compound leaf pattern
  • Fern-like leaves
  • Purple blotches on stem
  • Produces white flowers and seeds during its second year

Plant Longevity:

  • Biennial

Where Commonly Found:

  • Fence rows
  • No till fields
  • Pastures
  • Wood lines
  • Roadsides
  • Waste areas

Time of Most Concern:

  • Young plants in the spring

Compound that Causes Concern:

  • Coniine
  • Coniceine

Part of Plant Most Toxic:

  • All parts of the plant are toxic, however, younger plants and seeds are most toxic

Livestock Species Affected:

  • Cattle
  • Goats
  • Swine
  • Horses
  • Sheep
  • Poultry

Pasture, Stored Feed, Both:

  • Both

Clinical Signs:

  • Acute
    • Nervousness
    • Seizures
    • Dilated pupils
    • Excitation
    • Drooling
    • Slowed breathing
    • Irregular heartbeat
    • Frequent urination
    • Muscle tremors
    • Weakness
    • Depression
  • Chronic
    • Birth defects such as twisted limbs, scoliosis, twisted neck, or cleft palate
      • Cattle must ingest the plant at between 40-70 days of gestation for birth defects to occur
      • Sheep and goats must ingest the plant at between 30-60 days of gestation for birth defects to occur

Amount Needed to be Consumed for Clinical Signs / Death:

  • Signs depend on amount consumed
  • Signs appear 30 minutes to 2 days after consumption
  • 10-16 oz in cattle

Identifying Characteristics:

  • Low growing rosette first year of lifecycle
  • 3-8 ft tall second year of lifecycle
  • Alternate compound leaf pattern
  • Fern-like leaves
  • Purple blotches on stem
  • Produces white flowers and seeds during its second year

Plant Longevity:

  • Biennial

Where Commonly Found:

  • Fence rows
  • No till fields
  • Pastures
  • Wood lines
  • Roadsides
  • Waste areas

Time of Most Concern:

  • Young plants in the spring

Compound that Causes Concern:

  • Coniine
  • Coniceine

Part of Plant Most Toxic:

  • All parts of the plant are toxic, however, younger plants and seeds are most toxic

Livestock Species Affected:

  • Cattle
  • Goats
  • Swine
  • Horses
  • Sheep
  • Poultry

Pasture, Stored Feed, Both:

  • Both

Clinical Signs:

  • Acute
    • Nervousness
    • Seizures
    • Dilated pupils
    • Excitation
    • Drooling
    • Slowed breathing
    • Irregular heartbeat
    • Frequent urination
    • Muscle tremors
    • Weakness
    • Depression
  • Chronic
    • Birth defects such as twisted limbs, scoliosis, twisted neck, or cleft palate
      • Cattle must ingest the plant at between 40-70 days of gestation for birth defects to occur
      • Sheep and goats must ingest the plant at between 30-60 days of gestation for birth defects to occur

Amount Needed to be Consumed for Clinical Signs / Death:

  • Signs depend on amount consumed
  • Signs appear 30 minutes to 2 days after consumption
  • 10-16 oz in cattle

https://extension.entm.purdue.edu/newsletters/pestandcrop/article/poison-hemlock/

Beasely et al. Notes for Toxicology VB 320: A systems approach to veterinary toxicology. University of Illinois. 1994

Jordan, T. N., Goetz, R. J., & McCain, J. W. (1985). Poison Hemlock. In Indiana plants poisonous to livestock and pets (pp. 59–60).

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