See the blackthorn swim in snow
Bedecked with thorns so spiky it’s known as Nature’s barbed wire, the blackthorn’s delicate, starry-white flowers are also an often unreliable harbinger of spring, observes Jack Watkins
Hedgerows will soon be awash with white blossom amid sharp thorns. Will it herald a blackthorn winter, wonders Jack Watkins
ON drab days at the end of a long, cold winter, we become hedgerow detectives. The search is on for buds that are thickening and leaflets that are opening, clues that brighter, warmer, more colourful times lie ahead. The true change of the seasons can be a long time coming, however. Spring has many illusory dawns. A few days of genial sunshine, a mild westerly and joyful birdsong are ended abruptly by the return of the chill, the north wind whipping round to silence our avian friends once more. Yet nothing lulls the unprepared into a falser sense of hope than the blackthorn. Its March flowering, coming slightly ahead of its leaves, is undoubtedly a striking spectacle. The starry, white-petalled inflorescence lights up the lanes and hedgerows and jumps out from the edge of a dark wood. What is curious is that this creamy abundance pays no heed to temperature. In fact, it has been observed that the flowering often coincides with, or precedes, a cold spell. Over the centuries, superstitious rural folk have blamed the innocent species for ushering in the bitter plunge in temperatures, hence the term blackthorn winter. The blackthorn is generally classed as a shrub, not a tree, although I have often seen scraggy loners stretching up next to a stile or on the edge of a small copse, to between 12ft and 15ft in height. Occasionally, individual blackthorns can be found with substantial trunks, reaching up to 30ft. However, it is commonly a hedgerow shrub, forming the dominant species in about a quarter of hedges in this country. A British native, Prunus spinosa is unquestionably hardy and enduring. Duck behind it on a cool, blustery day and it’s the warmest of windbreaks, the sheltering, quietening effect as if you’ve stepped inside a shed and slammed the door shut. A long row of close-packed blackthorn has the impenetrable, bastion-like quality of a stonewalled medieval keep. It will last for centuries, so it is unsurprising that, with the hawthorn, it has long been a foundation block of a decent hedge. There’s evidence that its effectiveness as a formidable stock barrier was understood as far back as the Neolithic period (about 4,000bc–2,000bc) and it seems reasonable to assume that the great earthen banks and ditches that survive in our landscape from prehistoric times were once topped by rows of blackthorn. The drawback, which must explain why hawthorn was the shrub of choice during the parliamentary enclosures of the 18th and 19th centuries, is that it is challenging to work with. It produces new trees by suckering from underground runners off the roots, inconveniently often throwing them up away from the carefully laid hedge line. Once established, they are tough to uproot and, before long, you have a tangled thicket. In 1534, Sir Anthony Fitzherbert’s Boke of Husbandry, the earliest surviving tome to contain advice on hedge planting, urged landowners against it: ‘For that wyl grow outwarde into the pasture, and doth moch hurte in the grasse, and tearing the woll of sheep.’ The latter was a reference to the lethal thorns, which cause a nasty and painful inflammation if they penetrate human, equine or canine flesh (although they are not poisonous, as was once believed).
Yet blackthorn’s toughness makes it a superb nurse bed for other species in their early growth stages. Thus it has played a part in the well-documented rewilding scheme at Knepp Castle, West Sussex. Former arable land left fallow and ungrazed was colonised by blackthorn, together with hawthorn and other tenacious species, such as dog rose and bramble. They offered effective protection for tender tree saplings to establish themselves without being grazed off by foraging cattle, sheep and deer. Knepp describes these species as ‘Nature’s barbed wire’. Unlike barbed wire, blackthorn is a great host plant for other flora and fauna. Its closely woven, thorny thickets protect other plants growing beneath it, as well as small birds— whose preference is to nest only a few feet above the earth—such as the nightingale and yellowhammer. The rare, but beautiful redbacked shrike uses the thorns to impale its insect prey and blackthorn is the larval food plant of more than 150 insect species, including moths and the blacked-veined white, brown hairstreak and swallowtail butterflies. As the year progresses, blackthorn becomes an unremarked part of the hedgerow backdrop. Nevertheless, by September, the marbled blue berries, or sloes, offer a sober contrast to the brilliant red berries of the wild rose and the hawthorn. Squeezing the sloe reveals a green pulp. Eat it and the taste is bitter and sour. The acidity will make the inside of your mouth shrivel, but pricked sloes, bottled with sugar and gin, have long made for a classic countryside liqueur. For connoisseurs, smacking their lips and filling their glasses, even the perishing blackthorn winter is worth enduring to savour such bounty.