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Monkshood: toxicity, first aid and care

Monkshood (Aconitum napellus): severe for cats, severe for dogs, severe for small children. The toxic principle, the signs, what to do, and how to grow it.

Cats: SevereDogs: SevereChildren: SevereEmergency risk

Also sold as: Aconite, wolfsbane, ukanuia, käoking.

This is a reference table, not a diagnosis and not veterinary or medical advice. It cannot tell you how much of a plant matters for a particular child or a particular animal — that depends on body weight, on the part eaten and on how long ago. If a person or an animal has eaten part of a plant, phone the poison information centre or a clinician; do not wait for symptoms, and do not make anyone vomit unless you are told to.

What is in it

Toxic principle: Aconitine alkaloids — Alkaloids and other systemic poisons.

Aconitine holds sodium channels open in nerve and heart-muscle cells, so nerves fire continuously and the heart loses its rhythm. It is the most toxic plant commonly grown in northern European borders. It also crosses intact skin and mucous membranes, so this is one of the few garden plants where handling, not eating, is a documented route of poisoning. The tuberous root is the most concentrated part.

What it looks like when it goes wrong

Tingling and then numbness of the lips, tongue and fingers — an unusual and fairly specific early sign — followed by nausea, muscle weakness, visual disturbance and a dangerously irregular heartbeat.

What to do

Any ingestion is an emergency: poison centre or ambulance, veterinary clinic for an animal. For skin contact, wash with soap and plenty of water and seek advice if numbness or tingling develops. Always wear gloves when dividing or weeding around it, and wash your hands before touching your face.

Anywhere in the European Union, 112 reaches emergency services and can put you through. Lithuania's poison information bureau (Apsinuodijimų kontrolės ir informacijos biuras) publishes its own round-the-clock line; if you do not have it to hand, use 112. For an animal, your own veterinary clinic or its out-of-hours service is the first call — human poison centres do not advise on animals in every country.

How to grow it

A superb late-summer border perennial for this climate — deep blue hooded flowers on stiff stems that rarely need staking. Divide clumps every few years in autumn, gloved. Do not plant it where it will be weeded absent-mindedly, and never plant it in or near a vegetable bed.

What it gets confused with

The root is the problem: dug in autumn it looks like a small pale tuber and has been mistaken for horseradish and for Jerusalem artichoke, with fatal results in reported cases. If monkshood grows in your garden, it should not grow anywhere a root vegetable is ever lifted.

A plant that is not on the toxic lists

If you are deciding what to keep in a home with a cat, a dog or a small child, this one fills a similar role and is not flagged by the veterinary services.

Others that work the same way

Alkaloids and other systemic poisons — these behave alike, and what you would do about them is alike too.

Source: Royal Horticultural Society — potentially harmful garden plants · checked 2026-09-06

Care guidance is standard horticultural practice for a cool-temperate northern climate. Poison-centre numbers are listed on the hub page and are worth confirming against your own country's health service.

Frequently asked questions

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