Arborvitae
Thuja spp. (occidentalis, plicata)
Horse
Severe
Any suspected ingestion is an immediate veterinary emergency. Significant consumption (several hundred grams of branches).
Equio informs, it does not diagnose. When in doubt, call your vet.
What to do now
- Antidote
- No specific antidote. Symptomatic and supportive treatment (IV fluids, activated charcoal if recent).
- Time to signs
- A few hours to 24 hours
- Prognosis
- Guarded if kidney damage is advanced, but generally good if treated promptly.
- Contact veterinarian.
- Withhold feed.
- Administer fluids to support renal elimination.
- Activated charcoal if recently ingested.
Its ID card
- Height
- 5 m – 15 m (can vary significantly based on species and pruning)
- Flowering
- Not applicable (woody cones).
- Toxic parts
- Leafy branches (scales) and cones.
- Toxin
- Terpene ketones (Thujone)
- Habitat
- Garden hedges, property borders, parks, cemeteries.
- Soil indicator
- Tolerates all soils, often planted in garden soil.
- Regions
- All of Europe (Planted in hedges)
- In hay
- Yes — stays toxic once dried
- Palatability
- Low (very strong resinous taste). Poisonings almost always occur in winter with hedge trimmings or due to a complete lack of forage.
When the risk rises
Winter.
Spotting it in the field
Cypress (more rounded scales, less toxic), Savin Juniper (much more deadly). — smell : strong, resinous smell reminiscent of camphor or apple when crushed.
- Evergreen conifer with flattened, imbricated scale-like leaves.
- Very strong resinous smell (slightly apple/camphor-like) when crushed.
- Small, elongated woody cones.
Signs to watch for
Acute toxicity.
Dose : Several hundred grams of leafy branches for an adult horse.
- Colic and diarrhea (often first sign)
- Dark or bloody urine (kidney damage)
- Coordination disorders (ataxia)
- Muscle tremors
- In severe cases, convulsions and coma
Who is affected
Other species : Toxic to cattle, sheep, and dogs.
In pregnant mares : abortifacient (thujone causes uterine contractions).
Getting rid of it
Method : Remove plants if possible, especially if accessible to horses. Dispose of pruning waste safely (incineration or deep burial).
- Never discard Arborvitae hedge trimmings in or near pastures.
- Plant Arborvitae a safe distance from fences to prevent horses from accessing it.
- Ensure adequate forage availability, especially in winter, to prevent horses from seeking toxic substitutes.
Frequently asked questions
Can Equio identify Arborvitae from a photo?
It can help organize visual clues, but plant identification must remain cautious when horse health is at stake.
Is Arborvitae 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.