Everyone writes the "poisonous plants of summer" piece. Almost nobody warns you about autumn — which is odd, because autumn is when the emergencies actually happen. Trees drop their seeds, gardeners cut everything back, and spring bulbs go into the ground at exactly nose height. Three habits, one dangerous season.
This isn't a scare piece. Most of it is avoidable with about ten minutes of care. Here's the honest calendar, worst risks first.
01Why autumn, not summer
Summer plants are standing, full and bitter — animals mostly leave them alone. Autumn changes the maths. Seeds and berries fall to ground level. Hedges get trimmed and the clippings get dumped or piled. And a wilted or dried cutting is often more tempting to a grazing animal than the living plant, not less. The danger moves from "up there" to "right where the mouth is."
02The hazards, ranked worst to least
- Yew clippings. The single most lethal autumn mistake. Yew stays deadly even when dried — the toxin, taxine, isn't broken down by cutting, wilting or time, and half a pound can kill a pony. Every year animals die from trimmings tossed over a paddock fence "as a treat."
- Cherry laurel and cherry clippings. As laurel leaves are cut and wilt, crushed cells release hydrogen cyanide — a whole dairy group has died this way from hedge waste blown into a field.
- *Autumn crocus (Colchicum).* In flower September to October, and genuinely dangerous: every part contains colchicine, which can cause organ failure and death in pets. Do not confuse it with the harmless spring crocus — same shape, very different plant.
- Conkers and acorns. The two commonest autumn dog emergencies. Both are toxic and both cause gut blockages; a dog can be unwell within hours of chewing one.
- Newly-planted spring bulbs. Daffodil bulbs are the most toxic part of the plant, and a dog that watched you bury something is a dog that will dig it straight back up.
- Bonfire smoke. Never burn oleander or rhododendron clippings — their toxins don't vanish in the fire, and the smoke isn't something to stand in or breathe.
03The tidy-up rules that actually matter
- Bag toxic clippings, never pile or burn them. Yew, laurel, cherry, oleander and rhododendron trimmings go in a sealed bag to green waste — not a heap, not a bonfire, and never over a fence where livestock can reach.
- Fence lines are the danger zone. Most livestock poisonings are clippings landing where grazing animals can get them. Walk your boundary after cutting.
- Clear the wilted stuff same-day. Cyanide risk from laurel and cherry is highest as leaves wilt, so don't leave a cut pile out overnight near animals.
04If you have a dog
- Keep dogs on the lead under oak and horse chestnut trees in October — the ground is covered in acorns and conkers.
- Firm down and, if needed, net or cage newly-planted bulb beds. Wash your hands after handling daffodil bulbs before you touch the dog.
- Know your route to the emergency vet now, not at 9pm. Conker and acorn cases move fast.
05If you have a toddler
- Do an autumn eye-level walk: crouch to their height and look for red berries and hanging pods.
- Teach "we don't pick red things" as a firm rule — yew berries are the classic autumn temptation.
- If you don't know what a plant is, treat the berries as suspect until you've checked. Guessing is the risk.
How we checked this
Every care and safety claim on this page is verified against horticultural and veterinary sources.
Sources: Dogs Trust — conkers and acorns · RHS — yew growing guide · Purdue ADDL — yew toxicity persists in dried clippings (taxine) · Irish Veterinary Journal — cyanide toxicity in cattle from wilting laurel · Pet Poison Helpline — autumn crocus (colchicine) · ASPCA — daffodil · ASPCA — oleander
Checked 29 July 2026. If our advice ever conflicts with the RHS or ASPCA, believe them and tell us.