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Strychnine is a jungle plant!

May 11, 2010

Strychnine is a notorious nerve toxin which has been used to eradicate stray dogs and rodents in Asia, Europe and North America. The source is the seed of the jungle plant Strychnos nux-vomica (Loganiaceae). Two specimens grow naturally at Dokmai Garden, and this year the northern specimen carries plenty of fruit. The fruits are yellow and similar in size to oranges, but the peel is harder. When you crack one open, you will find a most appealing content; a glistering chanterelle-yellow pulp that smells heavenly of apricots. Indeed, the pulp IS edible, and some locals do eat it, but beware of the seed! The seed, and any other part of the tree, is heavily armed with strychnine, a natural insecticide.

The reason why strychnine import became illegal, was the fact that it degrades very slowly, i.e. if a rat eats a strychnine bait and dies, maybe a pig will find the rat and eat it, and then the pig dies. Then, an eagle finds the pig etc etc. A Mexican visitor said they still use strychnine to kill coyotes. Unfortunately her six dogs ate the coyote bait by mistake. Four dogs died, and two survived after being given antidote every 15 minutes throughout the night. The dogs where screaming due to painful cramps. There are chemotypes with much less strychnine, and such chemotypes are sometimes labeled S. nux-blanda. However, Flora of Thailand regards them conspecific, as there is no constant differing character.

Visitors to Dokmai Garden will notice that the leaves of the strychnine trees are eaten by insects, which seems strange. The insect is the larva of a hawksmoth, Macroglossum affictita (Sphingidae), which actually accumulates strychnine. The reason is to make birds spit (vomit?) when they try to eat a larva or an adult. The adult hawksmoth can be seen flying in daytime in the early rainy season, frequently visiting the nectar-rich Golden dew drop, Duranta erecta.

Eric Danell

Fruit peel, seeds and leaves of Strychnos nux-vomica.

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