Paliurus Mill.

The five or so species of Paliurus belong to a tribe (Paliureae) of the Buckthorn Family (Rhamnaceae) which are often thorny and often adapted to arid habitats. Within this tribe one genus (Ziziphus) bears fleshy fruit and includes the important fruit tree Z. jujuba; another genus (Hovenia) bears seeds with fleshy, edible pedicels. The fruit of Paliurus by contrast are dry, leathery and variously winged, a partial adaption for wind dispersal. Four species are native to temperate East Asia, while one (P. spina-christi) is a very common shrub from Mediterranean Europe and south-western Asia. The generic name derives from the classical Greek word for this tree (paliouros). Fossil evidence suggests the genus once enjoyed a much wider distribution across Eurasia and North America, spreading probably across high latitudes, before retreating abruptly around the end of the Miocene (Burge & Manchester 2008; Dong et al. 2015).

Lacking edible fruit or showily ornamental features, Paliurus have never become common garden plants, although the yellow blossoms, tiny but clustering in some abundance along the top of the zig-zagging twigs in late spring or early summer, are quietly attractive, as are the fruits, whose curious shapes can suggest some much larger kind of flower and which can ripen through yellow to a bright, rufous brown. Being tangled and fiercely spiny plants, several of the species also find some use as hedges within their native areas. In northern Europe, plenty of sunshine and good drainage seem to be requisites, though the alkalinity of the soil does not matter.

Two species, Paliurus hirsutus Hemsl. (native from SE China into northern Vietnam) and P. orientalis (Franch.) Hemsl. (endemic to SW China) are not known to be cultivated in the west and may not be hardy; they are excluded from this account. P. spina-christi Mill., the only one of the five species to be at all familiar in the garden, can be recognised by its spines, one of which stands erect while the other curves beneath the twig (a feature shared with many Ziziphus). In P. hemsleyanus Rehder and P. ramosissimus (Lour.) Poir. both spines in each pair are upstanding; both are Chinese trees, but the native distribution of P. ramosissimus extends south into Vietnam and north as far as Jeju Island (South Korea) and southern Japan; its fruits are significantly less broad and flattened and is the only one of the east Asian species to be deciduous (Royal Botanic Gardens, Kew 2024; Chen & Schirarend 2007).