This months Plant of the Month is ricinus communis, or more commonly the castor oil plant, a pretty shrub producing poisonous seeds.
Ricinus is a single species which lies within the euphorbiacae family and Ricinus communis originates from north west Africa and west Asia.
Seeds of ricinus have been found, thousands of years old, in Egyptian tombs.
The castor oil plant (or Indian oil plant – literal translation of its Turkish name) is a shrub which grows very quickly, forms its own groups by producing offspring, is evergreen and each plant has one main stem only.
It can be founded in temperate areas growing on waste ground where it has self-seeded.
This plant can grow to a height of 10 metres. In the first year it will reach a height of between 1 – 5 metre, but frost will kill it.
In tropical and subtropical regions it is a perennial, in other areas it can be grown as an annual shrub. It is upright with wide leaves forming 5 – 12 points some 15 – 40cm in length.
The leaves can be bright green, purple or even a reddish-bronze in colour.
The flowers of ricinus communis appear on stems some 30 – 40cm long as small balls.
In any group of these flowers the lower blooms are male and the upper ones are the females.
The round or oval berries are inside a prickly outer shell and are divided into three sections with one seed in each. The seeds are 8 – 20mm in length and can be one colour which varies from grey to dark red, or just like barbunya beans, they can be speckled all over.
The castor oil plant is easily damaged by frost. At -10C the shoots are damaged and -30C kills the whole plant. For the plant to spread the temperature should not fall below 20 – 25 degrees. It can withstand any amount of drought.
From first planting to the opening of the first flower takes 100 – 150 days.
Ricinus communis can be a very useful plant. It can be used as a repellent to keep animals that eat plants at bay because the seeds are extremely toxic for both humans and animals. For this reason the seeds should be handled with care and not ingested by children or pets. The poison in the seeds is called ‘ricin’ and forms 2.8 – 3% of each seed.
Thus anything from 3 – 20 seeds can kill a human being, 4 will do so for a rabbit, 5 for a sheep, 6 for a horse or cow, 7 for a pig, 11 for a dog and up to 80 for a chicken or duck. Small doses are not effective as rodent poison.
Many hybrid varieties of ricinus communis have been produced of which one of the best is ‘Carmencita’ which has dark red leaves and blooms.