Many of the most beautiful garden plants – including foxglove, lily of the valley, monkshood, yew, oleander, daffodil bulbs and hydrangea – are poisonous if eaten. Serious poisonings are rare, but children, pets and foragers who misidentify plants are at risk. Knowing what is in your garden, wearing gloves when pruning, and teaching children not to eat plants are the most effective safeguards.
Key takeaways
- Monkshood (Aconitum) is one of the most toxic plants in UK and US gardens – wear gloves.
- Foxglove and lily of the valley contain cardiac glycosides that affect heart rhythm.
- All parts of yew except the red flesh of the aril are highly toxic, including the seed.
- Lilies (Lilium and Hemerocallis) cause kidney failure in cats – even pollen.
- In an emergency: UK – call NHS 111 or 999; US – call Poison Control on 1-800-222-1222 or 911.
How common is plant poisoning?
Plant exposures are among the most frequent calls to poison centres, mostly involving young children who nibble leaves or berries. Thankfully, most cases cause no symptoms or only mild stomach upset because plants taste bitter and children rarely eat much. Severe poisonings are more often linked to adults mistaking a toxic plant for an edible one while foraging, or to pets.
12 poisonous garden plants
| Plant | Toxic parts | Main toxins | Typical effects |
|---|---|---|---|
| Monkshood (Aconitum napellus) | All, especially roots | Aconitine | Tingling, vomiting, dangerous heart rhythms |
| Foxglove (Digitalis purpurea) | All | Cardiac glycosides (digitoxin) | Nausea, visual disturbances, heart rhythm problems |
| Lily of the valley (Convallaria majalis) | All, including berries | Cardiac glycosides | Vomiting, slow or irregular heartbeat |
| Yew (Taxus baccata) | Needles, bark, seeds | Taxine alkaloids | Dizziness, heart failure |
| Oleander (Nerium oleander) | All | Oleandrin | Severe heart effects |
| Daffodil (Narcissus) | Bulbs especially | Lycorine | Vomiting, diarrhoea, abdominal pain |
| Hydrangea | Leaves, buds | Cyanogenic glycosides | Stomach upset |
| Rhododendron and azalea | All, including nectar | Grayanotoxins | Vomiting, low blood pressure |
| Laburnum | Seeds, pods | Cytisine | Vomiting, drowsiness |
| Deadly nightshade (Atropa belladonna) | All, especially berries | Atropine, scopolamine | Dilated pupils, hallucinations, racing heart |
| Castor oil plant (Ricinus communis) | Seeds | Ricin | Severe gastroenteritis if seeds are chewed |
| Lupin | Seeds | Quinolizidine alkaloids | Nausea, confusion |
Spotlight on the most dangerous
Monkshood
With its hooded blue-purple flowers, monkshood (also called wolfsbane) is a cottage-garden favourite, but it contains aconitine, which can be absorbed through broken skin. In 2014 a gardener on an English estate died after suspected exposure. Always wear gloves when handling it and never plant it where it might be mistaken for an edible root.
Foxglove
Foxglove gave medicine digitalis, a heart drug used since the 18th century after English physician William Withering studied it. That same potency makes it dangerous: its leaves have been confused with comfrey and borage leaves by foragers, with serious results.
Yew
Yew trees grow in churchyards across Britain, some over 1,000 years old (see the oldest trees in the world). The bright red fleshy aril is the only non-toxic part, but the seed inside is highly poisonous. Yew clippings are a common cause of livestock deaths.
Daffodils
Daffodil bulbs are sometimes mistaken for onions, and in the UK and Europe people have been poisoned after cooking them. Keep bulbs labelled and away from the kitchen.
Plants dangerous to pets
- Lilies: all parts of true lilies (Lilium) and daylilies (Hemerocallis) cause acute kidney failure in cats, even from licking pollen off their fur.
- Sago palm: extremely toxic to dogs.
- Oleander, azalea and yew: dangerous to dogs, cats and horses.
- Aloe vera: causes vomiting in pets – see aloe vera.
Dangerous lookalikes for foragers
- Hemlock and hemlock water dropwort look like wild carrot, parsnip and cow parsley; hemlock water dropwort is considered the most poisonous plant in Britain.
- Lords-and-ladies (Arum maculatum) leaves can be confused with wild garlic (ramsons); crush a leaf – only wild garlic smells of garlic.
- Autumn crocus has been mistaken for wild garlic, with fatal results in Europe.
- Foxglove leaves resemble comfrey and borage.
If in doubt, leave it out. When harvesting elderberries, read our elderberry safety tips.
How to stay safe
- Know your plants – keep plant labels and learn what grows in your garden.
- Teach children never to eat leaves, berries or mushrooms without asking an adult.
- Wear gloves when pruning or handling toxic plants and wash hands afterwards.
- Supervise pets, especially puppies and kittens.
- Never compost toxic clippings where livestock could reach them.
What to do in an emergency
- Remove any plant material from the mouth and keep a sample or photo of the plant.
- UK: call NHS 111 for advice, or 999 if someone is unconscious, having a seizure or struggling to breathe.
- US: call Poison Control on 1-800-222-1222 or use webPOISONCONTROL; call 911 for severe symptoms.
- Pets: contact your vet or an animal poison helpline immediately.
- Do not try to induce vomiting unless instructed by a professional.
Frequently asked questions
What is the most poisonous plant in a UK garden?
Monkshood (Aconitum) is often described as the most poisonous plant commonly grown in UK gardens. In the wild, hemlock water dropwort is considered the most poisonous plant in Britain.
Is foxglove poisonous to touch?
Touching foxglove is generally low risk, but all parts are toxic if eaten. Wear gloves when handling it if you have sensitive skin and wash your hands afterwards.
Which garden plants are poisonous to dogs?
Common plants toxic to dogs include sago palm, oleander, yew, azalea, rhododendron, foxglove, lily of the valley, daffodil bulbs and autumn crocus.
Are lilies dangerous to cats?
Yes. All parts of true lilies and daylilies, including pollen and vase water, can cause fatal kidney failure in cats.
What should I do if my child eats a plant?
Remove any plant from their mouth, keep a sample, and call NHS 111 in the UK or Poison Control on 1-800-222-1222 in the US. Call emergency services if they have severe symptoms.
