Daphne mezereum L. (Thymelaeaceae)

.

Mezereon


Daphne mezereum in mid-summer. 'Mezereon album. White Mezereon tree' collected by Jacob Bobart the Younger in the late seventeenth century, presumably from the Oxford Botanic Garden (Oxford University Herbaria, BJr-15-018)

Daphne mezereum is doubtfully native in Oxfordshire but has been part of the Botanic Garden's collection since 1648. Mezereon is a fragrant, usually pink-flowered, deciduous shrub which has been used for a variety of medicinal purposes. Giving a lecture in the Garden in the late-1780s, Professor John Sibthorp told his male undergraduates little about the plant's biology other than its root bark was used against 'venereal complaints'.

When the Oxford Botanic Garden was founded the focus of the collection was medicinal plants, as was common in the few other European botanical gardens at the time. However, within a few decades of its foundation, seventeenth-century catalogues and herbarium specimens show the Garden was replete with morphological forms and colour variants of numerous, often non-medicinal, plants. For example, by 1676, the Garden boasted a white-flowered mezereon variant. The first two Keepers (Jacob Bobart, father and son) had interests that inclined towards philosophical, and well as utilitarian, aspects of botany, they studied plants for their own sakes.

Distributed through Europe and western Asia, Daphne mezereum is a scarce native of British calcareous woodlands, and has been cultivated as an ornamental for centuries. However, despite the length of our association with mezereon our knowledge of its floral biology is poor. The tight clusters of nectarless mezereon flowers emerge directly from the leafless stems and form spectacular displays in the early spring when few other shrubs are in bloom. Each flower has a long tube formed from four, showy, petal-like sepals; there are no true petals. The form of the flower suggests long-tongued bees or butterflies may be pollinators, using floral scent as a reward. Mezereon scent is rich in linalool, a monoterpene alcohol attractive to a wide range of pollinators, but whether scent is an effective pollinator reward remains equivocal.

Mezereon usually produces abundant crops of bright red, fleshy, bird-dispersed fruits which appears to be contributing to its increasing range in Britain. In parts of North America, where it is introduced, mezereon is considered an invasive species, especially as it is highly toxic, due to the presence of mezerein and daphnin. Despite its toxicity, John Gerard, in his famous Herball (1597), reported mezereon as a treatment for drunkness; 'if a drunkard do eat one graine or berrie of this plant, he cannot be allured to drinke any drinke at that time; such will be the heate of his mouth and choking in the throte'.

Further reading

Andersson S et al. 2002. Floral scents in butterfly-pollinated plants: possible convergence in chemical composition. Botanical Journal of the Linnean Society 140: 129-153.

Church AH 1908. Types of floral mechanism. A selection of diagrams and descriptions of common flowers. Clarendon Press, p. 77-87.

Stephen Harris

BBC Radio Oxford clip about this week's plant