Botany Blueprint: The Castor Bean

Specimen #10: Castor bean, Ricinus communis

eaders of a certain generation might be all too familiar with Ricinus communis. The formidable shrub is more commonly known as the castor bean, a plant whose list of economic derivatives includes, most notably, castor oil. Once considered a cure-all elixir, castor oil has been used to remedy many ailments. It’s been enthusiastically applied as a hair tonic, topical ointment, and, of course, as a “cathartic” (or laxative). It is effective, but it is not gentle. In the late 1800s “age of heroic cures,” a treatment’s efficacy was often measured by its force.

And so, the plant secured a place in medicine cabinets through the mid-20th century. Not only a household healthcare remedy, the oil’s reliable strength was also employed in disciplinary regimens. Administered to mollify youthful insolence, it was even used in schools — a 1882 New York Medical Journal notes that “whatever laxity exists in that school is certainly not on the part of the teacher.”

Today, aisles of pharmacy offerings have replaced apothecaries and peddling druggists. And castor oil — as a health panacea, at least — is a bit of an anachronism. Meanwhile, the plant’s horticultural ubiquity has not suffered. Its continued utility and potency, augmented by an appropriately audacious appearance, ensure that the castor bean will not be shelved away in history’s medicinal ledgers.

The perennial shrub grows strong and vigorous in temperate and subtropical climates, and it reproduces prolifically. It’s still harvested for economic purposes. Castor oil is an ingredient in cosmetic creams, lipsticks, and lubricants (for machines, not the body). Castor also produces a toxic protein called ricin. The extracted poison has given the plant a sidebar in military history. In World War II, the United States and Britain employed ricin in their development of biological warfare agents. The ricin-enriched “Compound W” bomb was never implemented in combat, so it wasn’t until the Cold War that the castor’s white powder poison was regarded as a homicidal agent. In 1978, Georgi Markov, a dissident Bulgarian journalist, was assassinated while waiting at a bus stop. Forensics revealed a ricin-filled pellet, which had been embedded by a modified umbrella. Today, the CIA is apparently monitoring castor bean production in Iraq, and the Department of Commerce has prohibited North Korea from importing the plant.

The castor bean is not a friendly plant, and it at least gives fair warning. Looming sometimes forty feet tall, it’s covered with cautionary foliage. The leaves are large — up to three feet in diameter — with a dangerously reddish cast, and edged with deep serrations. The flowers are without petals; instead, they are composed of stigma clusters. Red, pink, or pale green, the fuzzy ornaments are surprisingly goofy. But this aesthetic levity soon turns grave, as the flowers are replaced by spiky fruits. Each capsule holds three or four ricin-filled seeds that are released from the plant when mature. The force with which they’re projected is known as “ballistic dispersal,” a term that’s fitting given their role in biological warfare.

And if the explosive propulsion doesn’t provide adequate distance, it’s likely that an ant will carry the seed even further. The protein-rich elaiosome is consumed by ants — a not uncommon dispersal strategy — and, in the case of the castor bean, it also absorbs water. The seed is suited to thrive even in dry conditions. Its lethality helps ensure that it will not be disturbed before germination, a note of warning that’s generously written in an unmistakably intricate design. While no two wear the same pattern, the unique motif is hard to miss — for animals, and also humans. The seeds are said to resemble swollen ticks, which hopefully reinforces the point. So while the castor bean, and its seeds, are among the most lethal in the botanic world, the plant graciously offers a number of visual noli me tangere warning signs. It’s easy to spot, and easy to avoid, though might deny culpability in the umbrella incident.

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