Castor bean is a small to almost treelike shrub growing to 10 or more feet tall, and having very large, palmately 5-11-lobed leaves.  The leaf margins are serrate and the blades can be as wide as 16".  Castor bean is monoecious with both male and female flowers on the same plant, the staminate below the pistillate.  Both male and female flowers have 3-5 sepals and no petals, the male flower has many clustered stamens, and the female flower has a 3-chambered bristly ovary and three reddish 2-lobed styles united at the base.  The pistillate calyx is early deciduous.  The fruit is a large, round, 3-celled, spiny capsule with smooth and shiny, brown, mottled seeds that resemble ticks, hence its name Ricinus which is the name of a Mediterranean sheep tick.  Castor bean flowers all year round and is a pernicious difficult-to-control weedy shrub of roadsides, fields and disturbed areas below 1000'.  It is native to Europe. Despite being the source of castor oil, the seeds are highly toxic and can be fatal if ingested.  These pictures were taken in lower Zuma Canyon in the Santa Monica Mts.

Click here for Latin name derivations: 1) Ricinus 2) communis.
Pronunciation: RIS-i-nus KOM-yoo-nis.
Click here for Botanical Term Meanings.