By Alastair Culham

The Christmas Cherry is a small, soft-leaved, shrub bearing many small white flowers through the summer that develop into bright orange-red fruit in the autumn.  It is in the nightshade family (Solanaceae) along with potatoes, tomatoes, tobacco and many other crops.

Christmas cherry photographed in my front garden in November

This shrub is generally sold as young plants 10-20cm high and 15-30cm wide by supermarkets and garden centres around the UK as a winter bedding plant.  The Christmas Cherry is much loved for its gaudy and long-lasting fruit.  It is just about hardy enough to stay alive through UK winters although it does tend to drop all its leaves if the weather gets too cold. It has been in  cultivation in Europe since at least the 18th century and is native to central and southern America.

An illustration of Solanum pseudocapsicum published in in 1792 in Plantarum indigenarum et exoticarum

An invasive species

Many garden plants in the U.K. have become established outside gardens but this species is perhaps too cold sensitive to establish and spread here.  There are a few records on the BSBI maps site centered around London while the National Biodiversity Network mapping system shows a large number of records in Bristol and surrounds. However, it is invasive in China and the U.S.A. among other places.

What botanical name does the Christmas cherry have?

I would usually, by now, have made a clear statement of the scientific name of the plant I was blogging about however there is some controversy over the taxonomy of the Christmas cherry.  Most of the literature on this species is under the name Solanum capsicastrum Link ex. Schauer (a.k.a. False Jerusalem cherry) and this name is accepted in the Royal Horticultural Plant Finder list.  However the Plant List (albeit with only two star confidence) says that Solanum capsicastrum is a synonym of Solanum pseudocapsicum L. var diflorum (Vell.) Bitter. (a.k.a. Jerusalem cherry) but then goes on to say “This name is the accepted name of an infraspecific taxon* of the species Solanum pseudocapsicum L. in the genus Solanum (family Solanaceae). * The Plant List does not attempt to include all infraspecific taxa”.  So, with grim determination I turn to the Solanaceae Source database, probably the most definitive list of species in the Solanaceae and the product of many years of detailed research.  Looking at Solanaceae source, S. capsicastrum appears as a synonym of S. pseudocapsicum but is not accompanied by a description.  The web site warns: “The names list on Solanaceae Source is a work in progress. Synonymy and nomenclature information are considered authoritative only for names that are accompanied by a full species description. For accepted names that do not yet have a species description, synonymy should be considered provisional.”

Digging in to the literature more deeply, the only comprehensive account for this species appears to be the treatment by Sandra Knapp in Flora Neotropica for the Solanum section Geminata. In this account she reports that “Solanum pseudocapsicum is a widespread and very variable species…. Cultivated forms are nearly always glabrous.”  This account makes a strong case to treat Solanum pseudocapsicum as one widespread and very variable species.  Working with Charlie Jarvis on the Linnean typification project they typified Solanum pseudocapsicum on material that reached Linnaeus via Madeira so it seems certain that this is the name to apply to our decorative Christmas Cherry.

The type specimen of Solanum pseudocapsicum from the Linnean Society Herbarium (LINN). Available on line at http://linnean-online.org/2508/

As a plant taxonomist I now feel happy that I can give the Christmas Cherry its correct botanical name, but less happy to know I’ve been using the wrong name  (along with most other people) up until now.

Tomorrow’s blog revisits cranberries.

References

Knapp, S. 2002. Flora Neotropica Vol. 84, Solanum Section Geminata (Solanaceae) (Jul. 30, 2002), pp. 1-404

KNAPP, S. & JARVIS, C.E. 1990. The typification of the names of New World Solanum species described by Linnaeus. Botanical Journal of the Linnean Society, 104 325–367, https://doi.org/10.1111/j.1095-8339.1990.tb02227.x