Castor Oil Plant: Growing and Safety of a Poisonous Ornamental Plant

In brief: The castor oil plant (Ricinus communis) is a fast-growing annual with conspicuous palmate leaves, grown here as an ornamental plant to a height of around 2 metres. The seeds contain the violently poisonous ricin and are dangerous if swallowed, so the castor oil plant is not suitable for a garden with small children or pets without strict supervision.

The castor oil plant is one of the conspicuous ornamental annuals that catches the eye in a bed with its large palmate leaves and fast growth within a single season. At the same time it is a plant for which clear safety rules need to be known, because the seeds are among the most poisonous plant parts an ordinary gardener can come across.

What the castor oil plant looks like and where it comes from

The castor oil plant comes from north-eastern Africa and south-western Asia, where in a warmer climate it grows as a perennial shrub. In central European conditions it is grown as a fast-growing annual; in European conditions it reaches a height of roughly 1.5 to 2 metres, in warmer summers more. Typical features are the large, palmately divided leaves and the conspicuous spiny capsules with seeds, which ripen gradually from summer to autumn.

Position, soil and growing

The castor oil plant likes well-drained, fertile soil in a sunny position, but also tolerates slight partial shade. Moderate to medium-generous watering is enough; the plant tolerates short-term drought better than long-term waterlogged soil. It is sown in spring after the last frosts, best first by raising seedlings in a container, because the plant needs warmth for a fast start to growth. Thanks to its fast growth, the castor oil plant in the garden also serves as a temporary green screen or a specimen in the middle of a bed.

Toxicity and safety – the most important information

The seeds of the castor oil plant contain the violently poisonous ricin, among the strongest plant poisons of all. According to available toxicological data, the lethal dose for an adult is estimated at 15 to 20 chewed and swallowed seeds; in children as few as 3 to 5 seeds can be potentially fatal. Symptoms of poisoning begin inconspicuously, similar to flu; later headaches, burning in the mouth, vomiting, diarrhoea and abdominal cramps follow, and in serious cases internal bleeding and organ failure within a few days.

The highest concentration of the poison is in the seeds, and the other parts of the plant contain smaller amounts. The castor oil plant therefore does not belong in a garden to which small children have unsupervised access, nor where pets or farm animals that could graze the seeds move freely. If you do grow the castor oil plant in the garden, remove the spent seed capsules in good time, before they ripen and fall to the ground, and always wash your hands after working with the plant.

What to do if you suspect poisoning

If a child or pet has swallowed a castor oil plant seed, or you have any suspicion of contact with the seeds, call the Toxicological Information Centre or seek medical help immediately, even if at first nothing serious is happening – symptoms of ricin poisoning may appear only after some delay. Do not wait until more marked problems appear, and definitely do not try to deal with the condition by yourself without consulting an expert.

Safe industrial use of the seeds

Despite their toxicity, castor oil is made from castor oil plant seeds by correct industrial processing, and after the ricin is removed it is used in cosmetics, in the food industry and as a laxative in medicine. This processing, however, requires expert procedures and it is neither suitable nor safe to try it at home with seeds from your own garden.

Placing the castor oil plant in the garden

Thanks to its fast and conspicuous growth, the castor oil plant suits as a focal point in the middle of a bed or as a temporary screen along a fence, where its large leaves form a dense green wall within a single season. If children or pets visit the garden, consider rather another ornamental plant without poisonous seeds, or plant the castor oil plant in a fenced part of the plot inaccessible to children and regularly check that seeds are not falling onto an accessible area.

Diseases, pests and resistance

The castor oil plant is fairly resistant to ordinary diseases and pests; any problems are related mainly to waterlogged soil, where root rot is a risk. In a cooler and damper summer aphids may appear on the leaves, but it is enough to rinse them off with a jet of water or treat them with a gentle product. The plant does not overwinter in our conditions and is sown again every year.

How to tell the castor oil plant from similar ornamental plants

Thanks to its large palmate leaves, the castor oil plant may at first glance be confused with some species of fig or with the Japanese maple, but the most reliable distinguishing feature is its spiny, globular seed capsules and its markedly fast, lush growth within a single season. The leaves are also often greenish to dark reddish-brown depending on the variety, which makes it a popular focal point in combination with other striking annuals too.

Why the castor oil plant is nevertheless grown in gardens

Despite the toxicity of the seeds, the castor oil plant is among the popular ornamental annuals thanks to its fast growth, striking leaves and easy cultivation from seed. In a large area of public greenery or in a garden without small children and freely roaming animals, it is an effective and undemanding focal point that in a single season grows to the size of a smaller shrub. The key to safe growing is being informed and following the basic rules, not excluding the plant from gardens altogether.

Frequently asked questions

Is it safe to grow the castor oil plant in a garden with small children?

It is not recommended without strict supervision. The seeds contain highly poisonous ricin and even a small amount can be dangerous for a child, so it is better to choose another ornamental plant or to plant the castor oil plant out of children's reach.

What should I do if a child or animal swallows a castor oil plant seed?

Contact the Toxicological Information Centre or seek medical help immediately, even if no symptoms are yet evident – ricin poisoning may show itself only after a delay.

Is contact with the leaves or stem of the castor oil plant also dangerous?

The highest concentration of the poison is in the seeds; the other parts of the plant contain the poison to a lesser degree. Nevertheless it is advisable always to wash your hands after working with the plant and not to touch your face afterwards.

Can castor oil be made at home from your own castor oil plant seeds?

No, processing seeds into safe castor oil requires expert industrial procedures that remove the ricin. Home processing of the seeds is dangerous and not recommended.

How long does the castor oil plant flower and fruit in the garden?

From summer to autumn, until the first frosts stop it. Here it is an annual plant that grows anew from seed every season.

Sources

• Wikipedia – Castor oil plant (Ricinus communis), toxicity and ricin
• Toxicological Information Centre (TIS) – help with poisoning by poisonous plants

Updated: 11 October 2026