Download Article 124 Castoroil revisit Ricinus communis

Weeds in our Area (Part One Hundred and Twenty Four)
By Bob and Ena McIntyre – Garden Route
Ricinus communis (Castor-oil Plant, Kasterolieboom)
Family: Euphorbia
The Castor-oil plant has been known for thousands of years and its oil was commonly used as a
lubricant and it is still used for medication today. Although both the seeds and the foliage are toxic
this does not affect the oil extracted from the seeds for medicinal purposes.
Large, conspicuous specimens of the Castor-oil Plant can be seen in several places in our village.
The plants favour disturbed areas and unkempt sites - along water courses, roadsides and fences.
Thankfully they are no longer popular as garden subjects – most likely because of the lethal
consequences of children ingesting the seeds.
A really fascinating description of this plant as garden subject dates back to 1953 and reads: “This
is a showy, tropical shrub” - suitable as an “ornamental where its exotic appearance is desired”.
The description continues with great enthusiasm about the ornamental qualities of the Castor-oil
plant - when the plants are still young the very large leaves are shiny and dark-red - the flowers
are non-descript but the fruit-bearing stems are suitable for the vase and also look good on the
bush. Ricinus communis was recommended for warm sunny well-drained positions facing north or
west in cold areas as well as being suitable for use as windbreak. A clear warning of things to
come is the particular comment that R.communis seeds itself so profusely in moist soils that there
are always new ones growing rapidly to about six feet in a single season. The fact that the seeds
are very poisonous and should be kept away from young children is also brought to gardeners’
attention.
Identification: In our area the
plants are perennial. They are
generally large shrubs with
glossy green or reddish green
foliage. They vary in height
from 2 to 4 metres. The leaves
are large (up to 300mm across)
and palm shaped with five to
nine lobes. The leaf margins
are finely serrated. The
insignificant small flowers
appear
on
long
stalks
throughout the year. The
flowers vary in colour from
reddish at the top to cream at
the bottom. The green fruits
are fat capsules covered in soft spines with three lobes. The seeds are very attractive but deadly
poisonous “beans” that look like mottled silver, brown and black beetles. Ingestion of the seed by
humans and animals is known to be lethal. Particularly attractive to children, the seeds are often
ingested by mistake with disastrous consequences.
Invasive Status: Declared invader (Category Two - may only be grown with a permit in controlled
conditions). It is a special effect weed, competitive in watercourses as well as being poisonous: the
whole plant and especially the seeds.
Control: Fortunately control is relatively simple as R.communis is sensitive to herbicides.
Registered herbicides for its control are available. Large specimens can be controlled by chopping
them down close to the ground and doing a cut stump treatment with triclopyr.
Indigenous substitutes: Melianthus major (Giant Honey flower), Bauhinia galpinii (Pride of De
Kaap), Duvernoia adhatodoides (Pistol Bush)
References: “ALIEN WEEDS AND INVASIVE PLANTS”: Lesley Henderson. Copyright © 2001
Agricultural Research Council. Problem Plants of South Africa: Clive Bromilow. Wikipedia.