Can they eat it? / Rhubarb leaves
Can horses eat rhubarb leaves?
No. Oxalates that damage the kidneys.
Garden rhubarb leaves over the fence are the usual route.
Drooling, colic, trembling, kidney failure.
Call your vet now. Note what was eaten, how much and when; do not wait for signs.
Why it is dangerous
Rhubarb leaves contain soluble oxalates, including oxalic acid and its salts. In the gut these bind calcium and can form crystals that damage the kidneys, and they can also drop blood calcium to dangerous levels. The stalks are less concentrated, but the leaves are the real risk. Because the damage is to the kidneys, it can build quietly and show up only after a meaningful amount has been absorbed.
How much is too much
For a 1,000 lb horse, there is no amount of rhubarb leaf that is considered safe to offer, so a single leaf is not a treat worth the risk. Pieces from a few leaves can be enough to cause trouble, and a large handful or more is a serious exposure. Ponies, miniatures and foals are smaller, so the same amount means a far higher dose per pound. Any amount eaten calls for a vet call.
Horses
Horses kept in a field or in work often browse fence lines, hedgerows and garden cuttings they find within reach. Walk the perimeter and check for rhubarb plants or clippings nearby, especially after the garden is tidied. Compost piles and yard waste bags are another common source. Remove any leaves you find and fence off the plants so they cannot be reached.
Ponies and easy keepers
Ponies, miniatures and easy keepers are more likely to pick at unfamiliar plants when grazing is limited or they are bored. Seniors may also be less alert to what they are grabbing. Keep these horses away from garden edges and clippings. Any suspected leaf eating in these animals warrants a prompt vet call, since small body size means a small amount can matter more.
Safe alternatives
Offer a few cubes of plain carrot or apple, cut into thin slices, as a treat that is safe for most horses. A flake of good quality grass hay or a handful of soaked beet pulp can also satisfy the urge to chew. Keep treats small and given by hand so the habit stays with what is safe.
Questions people ask
Is rhubarb in hay dangerous for horses?
Dried rhubarb leaves in hay are still a concern because the oxalates remain. Check hay carefully and remove any rhubarb before feeding, and call your vet if you find it in a bale that has been fed.
What if my horse ate rhubarb leaves after frost?
Frost does not remove the oxalates, so frost-damaged leaves are still dangerous. Call your vet right away, noting the amount and time, even if your horse seems fine.
Can a foal eat rhubarb leaves?
There is no safe amount for a foal, and their small size makes exposure more serious. Call your vet immediately if a foal has eaten any part of the plant.
Toxic for horses means: do not give it; if they ate it, call your vet or a poison line.
General information from veterinary guidance, not a diagnosis. If you are worried, call your vet or a pet poison line: ASPCA Animal Poison Control (888) 426-4435. Charges may apply.
Written by Hoofdeck editors · updated Nov 13, 2026 · from ASPCA Animal Poison Control, Merck Veterinary Manual and university extension guidance.