The attractive foliage and seed capsules of castor plant (Ricinus communis), also called castorbean, makes it a popular ornamental plant in gardens across the world. Its toxic seeds are used to make castor oil. The deeply lobed leaves, spiny seed capsules and multi-colored, spotted seeds are key to identifying this plant species.
Native to northeastern Africa to western Asia, castor plant will become tree-like in regions lacking frosts and freezes in winter. Here it can grow upwards of 30 feet tall and 12 feet wide.
In temperatre regions with growing seasons that are ended with a killing frost, castor plant is often grown as an annual or rejuvenating perennial. A height of 5 to 8 feet is possible with a width of 3 to 4 feet before the plant is killed by an autumnal frost.
Overall, castor plant is an erect shrub that forms branches along the main upright stems.
The leaves are perhaps the most distinguishing characteristic of this plant. Overall, each leaf is broadly oval but with 5 to 12 deeply cut lobes so that it looks like a star. The lobe edges are toothed and glossy, reflecting sunlight, and are medium green, reddish purple or bronze-red in color. The leaves are arranged alternately on the stems.
Flowers and Seeds
In the warmth of summertime, stem and branch tips form a 1-foot-long flower spike that hold rounded white to yellow-green flowers. The tips of the flower spike hold the female flowers, which have prominent red stigmas protruding from each blossom cluster. The male flowers are in the lower half of the flower spikes, also pale to medium green-yellow in color.
After pollination, the flowers become green spherical capsules that are covered in soft brown spines, very attractive in appearance. The capsule will split open when ripe and dry to reveal three oval seeds. The seeds are shiny and variably colored white, gray, brownish, yellow, brown, red, or black, with an outer pattern gray or brown to black. This outer seed pattern varies from fine to coarse, veined or finely dotted to large splotches, always intriguingly attractive.
Cultivated Variety Selections
Four cultivated varieties, or cultivars, are of note, as they are often used in gardens for their ornamental qualities:
'Carmencita' is a tall, well-branched plant with dark bronze-red leaves and red flowers.
'Impala' is short-growing, to waist-height, with red-purple foliage, yellow-green flowers and new leaves that are magenta red.
'Red Spire' has tall red stems with leaves that are bronze-green.
'Zanzibarensis' has large foliage that is green with white veins.
The seeds, or "beans" of the castor plant are poisonous and must not be ingested. Contact with the foliage and stems of the plant may also cause dermatitis, or skin rash or hives, in some individuals with sensitivities.
Because of the overall attractiveness of castor plant's foliage, curiousness of the spiny seed capsules and the colorfulness of the shiny seeds, it is not recommended for display or use near child playgrounds, parks or other gardens were children frequent without strict adult supervision.