Tree of the month: March 2023 - Blackthorn (Sloe)

Each month we will be featuring a species of tree found on Parkwood Springs. Visit our tree of the month page for further details here. This month we will be highlighting Blackthorn (Sloe).

The Blackthorn grows to a height of 6-7 metres and can live for 100 years. It has a dense growth and naturally suckers to produce thickets which, together with its long, strong thorns, make it a safe nesting and roosting site for many small birds and mammals, including the nationally threatened Nightingale and Turtle Dove. The same properties make it a valuable hedging plant.

The beautiful 5 or 6 petalled flowers appear in March, well before the leaves. Against the dark, almost sooty-looking branches the mass of flowers are a welcome display of early blossom. A cold spring is known as a ‘Blackthorn Winter’ and the early blossom is a source of nectar and pollen for many early bees, butterflies and other insects. The flowers can be crystallised. Early frosts, as with related species of plum, can diminish the later crop of fruit.

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Sloes, the blue-black fruit that appear in autumn, provide food for several bird species and are also popular for making the attractively coloured Sloe Gin, Wine or Jelly.

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Wildlife Value of Blackthorn/Sloe: A safe nesting and roosting site for some birds, Blackthorn is the most important food-source for the elusive Black Hairstreak Butterfly. This butterfly lays its eggs in autumn. They hatch in spring, the caterpillars feeding on the leaves. It is also important for the Brown Hairstreak and the caterpillars of several species of moth, including the Lackey and the Magpie Moth.

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Sloe berries are a valuable food-source for several species of birds, including the Hawfinch and the thrushes that arrive here in winter from Scandinavia and Continental Europe - the Redwing and Fieldfare. The ‘bloom’ that develops on ripening Sloe berries is a type of yeast and it is believed to enhance the reflection of UV (ultraviolet) light which may make the clusters of berries more visible to flocks of birds flying overhead. The Blackthorn is subsequently spread as the indigestible hard stones are defecated by the birds as they perch or fly off.

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Uses: Blackthorn wood is tough, knotty and gnarled and in addition to burning well it has long been used for things like walking sticks, marquetry, tools and the teeth of hay-rakes. It is the wood traditionally used in Ireland to make Shillelaghs, the clubs that were used to protect households and settle scores. It is still a symbol of Irish heritage, as seen in the logo of the American basketball team, the Boston Celtics.

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Recipe for sloe gin:
500g Sloes, best picked when plump and after first frost (Can also use Bullace or Damson). NB: Frost ‘blets’ the sloes, making them softer and more juicy. If you pick before a frost, put the sloes in a freezer for a day or two to simulate a frost.
250g of sugar (golden caster is good)
1 litre of gin (or you can use vodka)

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Wash sloes lightly, pat dry.
Each sloe needs to be pricked at least once- they used to say with a silver fork as the juice is very acidic. However you can use any fork or needle (and who has a silver one?- although my Grandmother kept one just for this purpose!)
Place in a jar or two with the sugar and gin, seal with a lid. (You can do this direct into a bottle if the bottle has a wide enough top for the sloes to be pushed into).
Shake well to dissolve the sugar, then turn or shake up every day or two for ten days, and occasionally after this. Leave in a cool, dark place.
Keep for 2-3 months before using. The liquid will go a gorgeous plummy colour.
Decant into bottles, straining from the sloes, although you can keep the sloes in.

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Sloes and their variants: Our native Sloe/Blackthorn is likely to be one of the parents of many of our varieties of damsons and plums, and they can cross naturally with related species. Sloes have quite small leaves, are dense bushes and always have multiple thorny side shoots, the ends of which may become snapped off over time. A common form of wild prunus is the Bullace. The name Bullace derives from the Middle English Bolas. Bullace are not thorny, have larger leaves and produce bigger fruit than Sloes but a little smaller than Damson. There is a purple-black variety of Bullace but Bullace fruit can also be white, yellow or green. Bullace is probably a cross between the sloe and cherry plum, but as they cross easily the main way to distinguish any variants from sloes is by leaf-size, growth-density and the presence of thorns! We do have Bullace variants on Parkwood Springs.

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The Mythology of Blackthorn: The Blackthorn is often associated with the darker side of the year and life (in reality the long thorns can produce a septic wound and act as a strong barrier) but their toughness is also associated with overcoming devastating difficulty and with protection. The medieval name for Blackthorn was ‘straif’ which is thought to be the origin of the word ‘strife’. In Celtic mythology the Goddess of winter emerges at Samhain, the 1st of November, to take over from Brighid, the Goddess of Summer. One of many images of the winter goddess is as the ‘dark crone of the woods’, gnarled and tough like Blackthorn wood, and depicted, a Raven on one shoulder, carrying a Blackthorn staff. Witches were said to use Blackthorn for their wands, to curse and cause trouble. In 1670 Major Thomas Weir of Edinburgh was burned, along with his Blackthorn staff, for witchcraft.

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In Irish folklore Blackthorn copses are guarded by spiky fairies called Lunantisidhe or Moon Fairies who are unfriendly to humans. They will curse you if you cut the wood during the fire festival of Beltane (30th April) or Samhain. The Moon Fairies were thought to only leave the Blackthorn during the full moon, to worship their Goddess, so that was believed to be the best time to pick the Sloe Berries.

Herbal uses: The berries, bark and leaves have been used to stimulate the metabolism, cleanse the blood and heal stomach upsets, to ease rheumatism and to treat sore throats.

Use as a dye: The bark, leaves and flowers yield a yellow dye and the fruit a blue or pink dye.

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A Blackthorn Winter (extract) by Ann Leahy
‘..spring was stark. Blackthorn in arthritic angles occupied a nether region, leafless, pricked with hard-nosed buds in pink, caught between death and regeneration, as if the year was loath to burgeon again, within the bark’.

Kipling (Puck of Pook’s Hill):
Of all the trees that grow so fair
Old England to adorn
Greater are none beneath the sun
Than Oak and Ash and Thorn.