The Castor Oil Plant ~ Medicine or Poison?

Ricinus communis is also known as castor bean, kasterolieboom, mohlafotha, mokhura or  umhlakuva.

Dr Google will rave about the medicinal properties of castor oil ~ it’s a laxative, moisturiser, wound healer and so on. But in the field it’s highly poisonous to horses, dogs and cats, and to a lesser extent to sheep, goats, pigs and cattle.

It’s not indigenous. In fact, according to CARA, it is a Category Two alien invasive. This means it is a plant with commercial or utility value that may only be grown with a permit under controlled circumstances in a demarcated area. (After extraction of the oil, the remaining ‘cake’ once heat-treated is a useful, high protein food source for cattle.)

If you find it growing on your plot you are legally obliged to remove it.

It is thought to have originated in East Africa and was introduced all over the world as an ornamental plant.

The seeds, used for making oil, contain ricin, a potent poison that damages animal tissue. The leaves are not nearly so toxic.

Ricinus communis is a long-lived, perennial shrub, which can grow to the size of a small tree in suitable conditions. It can vary greatly in its growth and appearance. The variability has been increased by breeders who have selected a range of cultivars for leaf and flower colours, and for oil production.

In some varieties they start off dark reddish purple or bronze when young, gradually changing to a dark green, sometimes with a reddish tinge, as they mature. The leaves of some other varieties are green practically from the start, whereas in yet others a pigment masks the green colour of all the chlorophyll-bearing parts, leaves, stems and young fruit, so that they remain a dramatic purple-to-reddish-brown throughout the life of the plant. Plants with the dark leaves can be found growing next to those with green leaves.

The stems (and the spherical, spiny seed capsules also vary in pigmentation. The fruit capsules of some varieties are more showy than the flowers.

Because the castor oil plant is alien and has no natural predators, it grows and reproduces freely, posing a problem to indigenous vegetation. It is particularly a problem in watercourses.

If prevention is not possible, it is best to treat the weed infestations when they are small to prevent them from establishing (early detection and rapid response). It is important to eradicate the plant before it seeds. Ricinus communis can be controlled through cultivation and mowing or physical uprooting. Burning may actually increase R. communis densities by plant regrowth and enhanced seed germination.