Castor bean warnings must be taken seriously

Published: Saturday, January 25, 2003 at 6:01 a.m.
Last Modified: Saturday, January 25, 2003 at 1:04 a.m.

It's not often that a landscape plant figures in international intrigue, but earlier this month, that's what happened to the castor bean plant.

Police searching a north London mosque that was raided in Britain's biggest anti-terrorism operation since Sept. 11, 2001, found tear gas and a stun gun.

Seven men were arrested during the raid, which was part of a wider probe into the discovery of the lethal poison ricin.

Earlier, a small amount of ricin was found in a flat in north London.

What is ricin? It is only one of the most poisonous naturally occurring substances known. The seeds of Ricinus communis are poisonous to people, animals and insects.

Perhaps just one milligram of ricin is enough to kill an adult. It causes abdominal pain and vomiting, severe dehydration and a decrease in blood pressure.

If the seed is swallowed without chewing, and there is no damage to the seed coat, it will most likely pass harmlessly through the digestive tract. However, if it is chewed or broken and then swallowed, the ricin toxin will be absorbed by the intestines.

Ricin, if injected into the blood stream, works quickly. In 1978, ricin was used to assassinate Georgi Markov, a Bulgarian journalist who spoke out against the Bulgarian government.

He was stabbed with the point of an umbrella while waiting at a bus stop near Waterloo Station in London. They found a perforated metallic pellet embedded in his leg that had presumably contained the ricin toxin.

As an ornamental, this is a really nice plant. Its large, stalked leaves consist of up to 11 pointed leaflets with slightly serrated edges and prominent central veins. It grows quickly from seed and can reach 15 feet high in a sunny location in a matter of months.

While most varieties are green, with inconspicuous green flowers, there are some that have a reddish-brown foliage and pink or red in the flowers. The mottled seeds are inside soft-spined fruits.

The genus name, Ricinus, means "dog tick" in Latin, because that's what the seeds look like.

The broad leaves can add a tropical look to landscpaes from south Florida through Georgia. It takes a little frost, but no hard freeze, and grows back from the roots eacy spring.

Castor beans are used as an ingredient in some animal feeds, but the deadly oil is rendered inactive by heating. Horses and sheep have been killed by browsing the plants and ingesting the feed, however.

While this poisoning of humans and animals is bad, the ricin has been tested as a "natural" insecticide. Aphids, drawn above on a leaf of the castor bean plant, are susceptible to poisoning from ingesting the phloem.

The European corn borer and the Southern corn rootworm larvae were killed when exposed to feed painted with 2 percent ricin.

Of course, the plant's seed is also the source of castor oil, a strong laxative with a legendary bad taste. It doesn't contain any of the toxic ricin, which is a water soluble protein.

The most responsible thing to do, if you choose to grow castor bean, is to remove the flowers before they are able to set seed. Wear gloves while doing this. This will also eliminate a lot of the volunteers.

Marina Blomberg can be reached at 374-5025 or by e-mail at

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