I decided to write this month about blackthorn, or sloe, the white-blossomed, early-flowering, native shrubby tree so often seen in hedgerows. Then I started doing some research, and discovered how complicated it all is, but I have tried my best …
In the first place, blackthorn (or sloe) is Prunus spinosa. Whitethorn is hawthorn (or may), Crataegus monogyna.
Thus the two thorns, though both in the Rosaceae family, are not very closely related to each other. Moreover, blackthorn can be easily mistaken for its closer relative Prunus cerasifera, the cherry plum, which also flowers early in the year, and has very similar leaves (though these tend not to show in either tree until after the flowering). The cherry plum does not have spines, and its flowers are pure white, while the blackthorn’s are supposed to be creamier.
In autumn, of course, the difference becomes very marked, as the blackthorn produces dark purple sloes with their distinctive bloom, while the cherry plum has (surprise!) cherry-like fruit.
Just to confuse life still further, there are several other non-native ornamental Prunus which flower in winter, though by and large they don’t produce significant fruit.
And there are other subplots like the bullace, categorised by some as a super-sloe, though in fact it is a small, wild plum, a subspecies of Prunus domestica (itself a hybrid of P. spinosa and cerasifera. (Moreover, what is called a bullace in East Anglia in not necessarily what is called a bullace in Wales.)
Finally, with regard to nomenclature, the blackthorn is so called because its bark is black.
As well as making excellent fuel, the wood is prized for transforming into a good, knobbly walking stick, knobstick or Irish shillelagh (with or without lead poured into one end for added heft): the rough-cut stick, ideally with root-wood attached, used to be cured first, by being greased with fat and hung in the chimney, so that it ended up black all the way through.
The low nature of the knobstick can be detected in this exchange between Margaret Hale and her mother in Elizabeth Gaskell’s North and South:
‘And if I live in a factory town, I must speak factory language when I want it. Why, mamma, I could astonish you with a great many words you never heard in your life. I don’t believe you know what a knobstick is.’
‘Not I, child. I only know it has a very vulgar sound and I don’t want to hear you using it.’
The plant itself is used for enclosures because of its close, thorny growth: a blackthorn hedge is supposed to be cattle-proof. The dried leaves can apparently used to adulterate tea, and the sloes ditto for port. They are also made into jams and other preserves, though this is traditionally done after the first frosts, which are believed to make them taste less tart (the same effect can be achieved by freezing them). Incidentally, Ötzi, the famous Bronze Age man found in ice in the Italian Alps, had sloes among his travelling provisions.
But of course sloes are best known as the vital component of sloe gin: not itself a distilled spirit, but an infusion (along with sugar) added to gin, to create a wonderfully ruby-coloured liqueur.
To give up the maximum of their juice, the sloes should be pricked either with a thorn from the bush, or a silver fork or needle – no other metal can be used. (Again, if you don’t have the time or patience, freezing them splits the skins.) Slowness is the key: in addition to the taste of the fruit, the kernels give up their faintly almond flavour (prussic acid, anyone?) if the mixture is left long enough.
Recipes vary according to personal taste (there are several competitions around the UK for the best home-produced sloe gin), and the alcohol by volume can vary from 15 to 30 per cent, though the EU has helpfully ruled that to count as ‘real’ sloe gin, it must have a minimum ABV of 25%. Damson gin can be made by a similar process, and sloe-flavoured liqueurs are also produced in Spain (pacharán, with anise as its base, yuck), Italy (bargnolino, 40–45% ABV (!)), and Germany (Schlehenlikör, which can use gin, vodka or rum).
Altogether, then, a useful plant, and it must have been a very cheering one, as a harbinger of spring, before the arrival of early-flowering prunus, daphnes, and other trees from the Far East in the eighteenth and nineteenth centuries.
As hedgerows have declined across Britain, the blackthorn is less frequently seen, though there are some (currently) spectacular stands alongside the Cambridge to London railway line, and I know of another not far from Cambridge – which however I must not publicise, or I will be in trouble with the people who rely on it every autumn for their sloe gin.