Crops Castor oil (Ricinus communis)

Summary Information



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Young plants

Castor plants can be very variable in appearance. Naturally, the species is a fairly tall branched perennial, but forms cultivated for seed production are erect and relatively short (to 1.5 m), and grown as annuals; there is also variation in the colouration, particularly in ornamental types. The plant has a well- developed taproot with many lateral branches. The stem is round, with a waxy bloom, the nodes being prominent, each giving rise to a single leaf.

Fully grown crop

The leaves are large (up to 50 cm across), glossy green and fan-like with pointed lobes and prominent veins, each developing on a long stalk.

Flower spike

Flowers are produced in spikes, male flowers being positioned below female ones; the flowering period may be long.

Green seedpods

Spike of ripe seedpods

The fruits are spherical capsules, often spiny, becoming hard and brittle when ripe, each usually containing 3 seeds. The regions in which castor may be grown commercially are restricted by lack of frost-tolerant crop types, and the need for high temperatures (about 25 C) and low atmospheric humidity to obtain good yields; however the crop can perform well in semi-arid conditions. It is suggested that a seedbed should be prepared in the same way as that for maize, seed being planted some 5 cm deep in rows about 1 m apart, to establish a population of about 3 plants per square metre. Weed control is essential; some pre- emergence herbicides may be suitable but subsequent measures are also likely to be needed. It is uncertain whether pests and diseases of the crop in tropical areas will also become problems within Europe. Suggested fertiliser requirements are 75 kg per ha of nitrogen and 25 kg per ha each of phosphate and potash. Harvesting may be performed by machines which use a beating action to remove the pods, which are subsequently shelled out: it is expected that yields of up to 2 t seed per ha may be obtained. Present work seeks to define suitable agronomic practice for castor production in Southern Europe; breeding goals include improvement in seed yield, oil content and ricinoleic acid content. The total market requirement is likely to increase as further products which use the oil are developed. The breeding of a genetically-modified form of oilseed rape, producing ricinoleic acid, is under active development, but it seems unlikely that this would replace castor where this can be grown economically.