Paliurus spina-christi Mill.

In its native maquis habitats Paliurus spina-christi can be a common, even a dominant plant, inconspicuous in terms of its foliage and low, tangled habit but pretty in late spring when its greeny-yellow flowers cluster above the zig-zagging stems, and quite showy in late summer when its circular-winged drupes ripen like fairy-sized sombreros; these can hang on into winter. The autumn colour can be a good yellow and the leaves tend to droop rather neatly below each twig.

Online sources sometimes describe these drupes as edible, but that derives from confusion with the Jujube, Ziziphus jujuba, a tree which is quite closely related and indeed very similar in terms of its foliage, but which bears fleshy fruit. In Paliurus by contrast the drupe is dry and leathery and has evolved to allow dispersal by the wind. A further source of confusion between these two genera lies in the existence of Ziziphus spina-christi, a shrub from arid habitats in sub-Saharan Africa eastwards to Pakistan which cannot be grown out-of-doors in northern Europe. The specific name of both of these plants derives from the belief that their spiny, flexible branches were used to fashion Christ’s crown of thorns.

Although it is not edible, Paliurus spina-christi is an easy plant to grow – given plenty of summer warmth and sunshine, and a free-draining soil – and widespread cultivation has obscured the limits of its natural distribution. It is scarcely a timber tree, but its whitish-pink wood is tough and its seeds have various traditional uses in herbal medicine (Zor et al. 2017). It travelled eastwards along the Silk Road long ago, reaching China where it is naturalised in Shangdong province at least (Chen & Schirarend 2007); some authorities have suggested that it is genuinely native across this zone. It is also naturalised along the Mediterranean coasts of Africa (Royal Botanic Gardens, Kew 2024) and in Texas, where it has spread from hedgerows planted in the 1880s and forms thickets along the flood-plain of the Pedernales River (Nesom 2016). This population excepted, the species now seems to be rare in North America; there are specimens at the C.R. Keith Arboretum in North Carolina (Hatch 2024) and at the Denver Botanic Gardens, Colorado (Royal Botanic Garden Edinburgh 2023).

Its general toughness makes Christ’s Thorn one of the most strictly ‘Mediterranean’ trees to be more or less at home in the cool and cloudy climate of Britain; even in the colder winters of the start of the 20th century it grew unharmed at Kew (Bean 1976). It was in cultivation by the 17th century at least, and in the 1830s an old tree at Syon west of London was described, rather remarkably, as 10 m tall with a 9 m spread (Loudon 1838). This specimen has long gone but another ‘ancient’ bush survives at Ham House across the Thames, where it sprawls widely beside the orangery (Tree Register 2024). At Cambridge University Botanic Garden, in England’s most ‘continental’ microclimate, it even flowers well in shade (Cambridge University Botanic Garden 2024), while Matthew Ellis manages to grow it in his Grange Farm Arboretum in the very moist and rich soils of the Lincolnshire Fens. The collection Schilling 3189 failed, however, in the more northerly and cooler conditions of Ray Wood at Castle Howard in Yorkshire (Tree Register 2024). The species remains commercially available in the UK from a couple of specialist suppliers (Royal Horticultural Society 2024).