Hemlock Water Dropwort
Oenanthe crocata
Horse
Critical
Any suspected ingestion is an immediate veterinary emergency. A single root (the size of a small carrot) is enough to kill a horse.
Equio informs, it does not diagnose. When in doubt, call your vet.
What to do now
- Antidote
- No specific antidote. Intensive symptomatic treatment: anticonvulsants, respiratory and cardiac support.
- Time to signs
- 15 minutes to a few hours
- Prognosis
- Desperate. Death occurs in the majority of cases due to respiratory exhaustion and cardiac arrest during a seizure.
- Absolute life-threatening emergency.
- Administration of potent anticonvulsants (diazepam, barbiturates) by the veterinarian to stop seizures.
- Gastric lavage if the animal is stabilized.
Its ID card
- Height
- 30 cm – 1.5 m
- Flowering
- June to August
- Toxic parts
- The entire plant, but the root (tuberous, shaped like a small dahlia/carrot) is a true toxic bomb.
- Toxin
- Polyacetylenic alcohols (Oenanthotoxin)
- Habitat
- Banks of rivers, streams, flooded ditches, marshy meadows.
- Soil indicator
- Flooded, muddy soils, freshwater banks.
- Regions
- Western Europe, Atlantic Basin, United Kingdom, France (Brittany/West)
- In hay
- Yes — stays toxic once dried
- Palatability
- This is the tragedy: the root has a sweet, pleasant taste (like carrot/parsnip). Horses easily dig it up in the mud or eat it if it's uprooted during ditch clearing.
When the risk rises
Winter and Spring (when roots are fleshy and the soil is loose).
Spotting it in the field
Wild celery, Wild carrot, Hogweed, Water hemlock (equally deadly). — smell : characteristic smell of celery or parsley, especially when crushed.
- Aquatic/bankside plant (Apiaceae family).
- Highly dissected leaves resembling celery.
- White flowers in umbels.
- Broken roots exude a yellowish sap that turns saffron-colored in the open air.
- Smell of parsley/celery.
Signs to watch for
Acute toxicity.
Dose : A single root (size of a small carrot) can be lethal for a horse.
- Extremely violent convulsions (epileptiform seizures)
- Hypersalivation (abundant foam)
- Pupil dilation and staring gaze
- Extremely clenched jaws (trismus)
- Asphyxiation and death within hours, sometimes less
Who is affected
Other species : Lethal to humans (often fatal for wild foragers), cattle, sheep, dogs.
In pregnant mares : death of the mare.
Getting rid of it
Method : Uproot the entire plant, including roots, before flowering. Wear impermeable gloves. Destroy uprooted plants by incineration or deep burial.
- Identify and remove the plant from pastures and water sources.
- Prevent horses from accessing banks and ditches where the plant is present.
- Do not leave uprooted roots on banks after ditch clearing.
- Provide clean and safe drinking water.
Frequently asked questions
Can Equio identify Hemlock Water Dropwort from a photo?
It can help organize visual clues, but plant identification must remain cautious when horse health is at stake.
Is Hemlock Water Dropwort dangerous in hay?
This entry flags hay vigilance. Isolate suspicious forage and ask for professional advice if exposure is possible.
This page is informational. If ingestion is likely, if signs appear, or if the horse is fragile, contact a veterinarian immediately.