A vigorous tender perennial or shrub, which is usually grown as an annual in the UK. Loved for its large ornamental leaves, which provide an exotic look to the garden.
Family: Euphorbiaceae (spurge family)
Botanical Name: Ricinus communis
Common Names: Castor oil plant, palma christi, ricin plant, wonderboom
Foliage: Large palmate leaves, which differ in colour according to variety.
Flowers: Tiny flowers borne in thick panicles, followed by prickly seed capsules (pods).
Flowering Period: Mid-summer to early autumn.
Soil: Moist but well-drained, fertile soil (chalk, sand or loam). Any pH.
Conditions: Best in full sun, will tolerate some shade. Grows best in a west or south facing aspect.
Habit: Bushy, branching.
Type: Evergreen shrub grown as a half-hardy annual in the UK.
Origin: Africa, East India.
Hardiness: Half-hardy in the UK. Protect from frost.
Toxicity: All parts of the plant are highly toxic if eaten and can irritate skin and eyes. Wear gloves when handling and wash hands afterwards.
Best planted in a fertile sandy loam, in a sunny situation. Add plenty of organic matter or garden compost to the soil when planting. Plants grown on poor soils tend to produce more flowers at the expense of foliage. Do not plant outside until all danger of frost has passed in your area.
Ideal as specimen plant or a focal point in a bedding scheme. Can also be planted in large containers, which will help restrict growth.
As castor oil plants are highly toxic it is best to keep them well out of reach towards the back of the border.
Apply a balanced fertiliser every month and water plants liberally as needed.
Stake plants in exposed locations.
No pruning necessary. For safety the seed heads can be removed before they ripen.
Ripe seeds can be saved for next season but are notoriously toxic so must be stored with caution.
At the end of the season, pull up and discard plants on the compost heap.
Susceptible to attack by red spider mite. Generally disease free.
Sow seeds into small pots under glass from February to April, at 18-21°C. Pre soak seeds in tepid water for one day prior to sowing. Pot on, harden off and plant outdoors once all danger of frost is past. Wear gloves when handling and wash hands afterwards.
Ricinus communis is the main garden species grown in the UK. It has large, glossy, red, purple or green foliage (depending on variety), with showy flower spikes and pods. Cultivars include: