Common Walnut
Juglans regia
Horse
Low
Remove access and monitor the horse; call at the first sign. A very high consumption of nuts (with the green husk) or permanent contact (bedding/shavings).
Equio informs, it does not diagnose. When in doubt, call your vet.
What to do now
- Antidote
- No specific antidote. Symptomatic and supportive treatment.
- Time to signs
- A few hours to a few days.
- Prognosis
- Very good. The tree is more of an autumnal 'nuisance' (leaves killing grass) than a mortal danger to horses.
- Remove access to the plant.
- Monitor the horse's general condition.
- Observe the consistency and frequency of droppings.
- Check hoof warmth for early detection of laminitis.
Its ID card
- Height
- 15 m – 30 m
- Flowering
- April to May.
- Toxic parts
- Walnut husk (green outer layer of the nut), moldy fallen leaves, wood (shavings).
- Toxin
- Juglone (very low dose compared to Black Walnut) and associated fungi (mycotoxins).
- Habitat
- Orchards, farmyards, pastures, property edges.
- Soil indicator
- Deep, rich, well-drained, sunny soils.
- Regions
- Entire Europe (Wild and cultivated)
- In hay
- Not reported
- Palatability
- Low (bitter and aromatic leaves). Some greedy horses learn to chew fallen nuts in autumn, primarily risking digestive obstructions or ingestion of molds.
When the risk rises
Autumn (falling leaves and nuts) and Winter (shavings).
Spotting it in the field
American Black Walnut (whose green husk is very granular/rough and which is much more toxic). — smell : characteristic acrid/peppery smell of leaves when crushed.
- Classic large tree.
- Light grey bark, smooth then fissured.
- Compound leaves with 5 to 9 broad, light green leaflets.
- Characteristic acrid/peppery smell when crushed.
- Large, round green fruits (husk) containing the nut.
Signs to watch for
Primarily acute through ingestion of large quantities or prolonged contact with moldy shavings.
Dose : Not established for horses, but significant consumption of moldy nuts or husks can be problematic.
- Dark diarrhea and mild colic (ingestion of walnut husks or green leaves)
- Very exceptional mild laminitis (via wood shavings or massive ingestion of moldy walnuts)
- Irritation of skin or respiratory tract (horse bedded on dead walnut leaves)
- Very dark urine (walnut stain)
Who is affected
Other species : Moldy walnuts (penitrem A) are highly neurotoxic (fatal) to dogs.
In pregnant mares : no specific risk.
Getting rid of it
Method : Pull up young plants if possible. Collect and dispose of plant debris (leaves, nuts).
- Avoid using walnut shavings for bedding.
- Regularly clear paddocks of fallen leaves and nuts, especially in autumn.
- Monitor horses prone to eating unusual items.
Frequently asked questions
Can Equio identify Common Walnut from a photo?
It can help organize visual clues, but plant identification must remain cautious when horse health is at stake.
Is Common Walnut dangerous in hay?
Hay risk is not always reported for this entry, but suspicious forage should still be isolated until checked.
This page is informational. If ingestion is likely, if signs appear, or if the horse is fragile, contact a veterinarian immediately.