Plant 75

Calycanthus floridus L. (Calycanthaceae)


Carolina allspice

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Calycanthus floridus is a deciduous shrub, grown as an ornamental curiosity, with an assortment of common names, all of which emphasise it is fragrant and aromatic. This shrub is native to the southeastern USA, including Florida, although the specific epithet is a reference to its profuse flowering rather than its native range. One of its common names, Carolina allspice, also emphasises the northern limit of its range.

As a forest understorey shrub, Calycanthus floridus spreads by suckering, but is not sufficiently vigorously to be an invasive species. The beetle-pollinated flowers, typically a dark, burnished red are showy and scented, but sometimes hard to see against the dark green leaves. One selection from the University of Georgia Botanic Garden with yellow-green flowers led to the cultivar 'Athens'.

With the support of the naturalist William Sherard, the diplomat who endowed the Sherardian Professor of Botany in Oxford, and a cartel of wealthy patrons, the English naturalist and artist Mark Catesby undertook a four-year plant collecting expedition to the southeast USA between 1722 and 1726. He subsequently published Natural History of Carolina, Florida and the Bahama Islands (1729-1747), which was illustrated with his own images. His legacy includes many depictions of birds from these regions, illustrated together with native plants, hundreds of plant specimens archived in Oxford University Herbaria and an early study on migratory birds. Calycanthus (although not yet named this) was noted in the woodlands of Piedmont Carolina as being as 'odoriferous as cinnamon'. All parts of Calycanthus are aromatic. An oil distilled from the shrub is used in perfumery, there is even a rather spicy, woman's fragrance called Calycanthus.

However, all is not as sweet as it first seems. Calycanthus is the source of the alkaloid, calycanthine, which has a similar structure to strychnine. Carolina allspice is noted to be good for planting in gardens where deer are a problem. Indeed, Calycanthus is reported to have been the cause of sheep and cattle deaths due to the toxicity of its alkaloids. Calycanthine is a convulsant, acting by inhibiting the release of the inhibitory neurotransmitter gamma-aminobutyric acid. Calycanthine was first isolated in 1888, but it was not until the mid-twentieth century that the chemical structure was determined. Sir Robert Robinson, Nobel Laureate and Professor of Chemistry at the University of Oxford, is co-credited with elucidating the structure of calycanthine and with the initial proposal outlining its biological synthesis inside the plant.

Further reading

Nelson CE and Elliott DJ 2015. The curious Mister Catesby. The University of Georgia Press.

Alison Foster