There's a comfortable assumption behind most compost advice: that a dead plant is a harmless plant. For a lot of the garden, that's true. But for a handful of common shrubs and climbers, drying and wilting don't neutralise the poison — they either leave it intact or actively make it worse. Get this wrong near livestock and the result isn't a sulking plant. It's a dead one, or a dead horse.
The honest, un-obvious science here is that drying does different things to different poisons. So there's no single rule for the clippings barrow. There are four.
01Yew: dries lethal, stays lethal
Yew's toxin, taxine, does not break down as the foliage dries. A clipped, browned yew branch stays as dangerous as the day it was cut — sometimes more so, since the alkaloids sit at their highest concentration over winter. This is exactly why yew is one of the classic causes of sudden livestock death: animals rarely touch the living hedge, but they'll eat wilted clippings tossed over a fence, and a mouthful can stop the heart with no warning signs. The RHS treats all parts (bar the fleshy aril) as toxic and tells you to glove up even for handling.
Verdict: compost only in a sealed home heap well away from grazing animals — never dump, never pile within reach of a field.
02Clematis, hellebore and the buttercups: drying makes them safer
Here's the reversal. The irritant in clematis and its buttercup-family cousins (including hellebore) is protoanemonin, the compound behind the blistered skin some gardeners get from the fresh sap. Protoanemonin is unstable. As the plant dries, it converts to anemonin, which is not a vesicant — the dried, dead material is generally considered safe. This is the same reason dried buttercup in hay loses most of its bite.
Verdict: safe to compost. Wear gloves with the fresh trimmings, then stop worrying once they've dried.
03Cherry laurel and the prunus family: wilting makes them worse
Cherry laurel, common laurel and ornamental cherries carry cyanogenic glycosides. In an intact leaf, the compound and the enzyme that unlocks it are kept apart. Crushing, freezing and — critically — wilting bring them together, releasing hydrogen cyanide. That means a heap of wilting laurel prunings is more dangerous than the living hedge, not less. Wilted leaves can carry higher cyanide levels than fresh ones, and there are documented cattle deaths from animals reaching clippings piled by a fence. As little as a couple of pounds of wilted leaves can be lethal to a cow, often within the hour.
Verdict: never compost or dump anywhere livestock can reach. Bag it, or hot-compost sealed and away from animals. Never leave it wilting in an open heap by a paddock.
04Oleander and rhododendron: safe to bag, never to burn
Some prunings are only dangerous if you try to get rid of them the "tidy" way. Oleander holds cardiac glycosides and rhododendron holds grayanotoxins, and both survive burning — the smoke carries the toxin. Inhaling it, or eating anything cooked over it, is a genuine poisoning risk. Composting is the safer route; the fire is the trap.
Verdict: never burn. Compost or bag for green waste instead.
05The quick verdict, in order of danger
- Yew clippings — most dangerous. Toxin survives drying. Never within reach of livestock; sealed disposal only.
- Wilting laurel/cherry (prunus) — wilting releases cyanide. Never compost or dump near grazing animals.
- Oleander and rhododendron — compost or bag, but never burn; the smoke is toxic.
- Clematis, hellebore, buttercups — the easy one. Drying destroys the irritant; safe to compost.
How we checked this
Every care and safety claim on this page is verified against horticultural and veterinary sources.
Sources: Cornell University CVM — Taxus (yew) toxicosis · RHS — Yew · University of Kentucky — equine safety and buttercups (protoanemonin to anemonin on drying) · ASPCA — Clematis · VPIS — cherry laurel and other cyanide-containing plants · ASPCA — Oleander · ASPCA — Rhododendron
Checked 29 July 2026. If our advice ever conflicts with the RHS or ASPCA, believe them and tell us.