Barberry
Berberis is a genus of shrubs found throughout temperate and subtropical regions. It is the most speciose genus in the family Berberidaceae, which also includes genera familiar to gardeners such as Nandina, Epimedium and Mahonia. Many members of the family have a bright yellow inner bark due to the presence of the alkaloid berberine. Berberine is not unique to the Berberidaceae. It is found in genera of families, such as Papaveraceae and Ranunculaceae, that have yellow tissues inside their roots and stems. Berberine has been used as a traditional source of yellow dyes. Under ultraviolet light, it fluoresces yellow and is useful as a histological stain.
The genus Berberis is readily identified by the combination of yellow inner bark and the presence of sharp spines along the stems and on leaf margins of many species. The pleasant, sweet-scented flowers are usually small, bright yellow, radially symmetrical and hang down in loose clusters. Berberis darwinii is frequently used in gardens because of the abundance of flowers it produces. The fruits are usually a bright red, as in Berberis thunbergii, or a deep blue, as in Berberis darwinii, with a blue-white powdery bloom of epicuticular wax, resembling that frequently found on grapes. Species range in size from about one metre to four metres tall, and have numerous, small, tightly packed leaves. In cultivated varieties, leaves may turn deep red in the autumn.
Berberis species have been used in Chinese folk medicine for millennia, whilst initial clinical trials suggest that there may be effects on blood lipids or diabetes. In addition to their use in traditional medicine, Berberis species have proven useful as effective hedgerow species to control livestock and protect property. In addition, numerous Berberis species have proven to be valuable garden plants.
The bitter berries of Berberis, although edible, are not widely consumed. In parts of Europe and Iran they are used to make preserves. In Iran they are also dried and mixed with rice. The difficulties of harvesting barberries means they are not commercially available.
Many Berberis species are invasive outside of their native ranges. Moreover, they are the intermediate host of wheat stem rust, which means that in wheat-growing areas the occurrence of Berberis can have serious consequences for grain production. The relationship between cereal rust and Berberis occurrence has been known in Europe since at least the sixteenth century, long before the biology of the situation was understood.
Further reading
Ju J et al. 2018. Efficacy and safety of berberine for dyslipidaemias: a systematic review and meta-analysis of randomized clinical trials. Phytomedicine 50: 25-34.
Stakman EC and Fletcher DG 1930. The common barberry and black stem rust. US Department of Agriculture.
Robert Taite