Foraging Guide: Sloes

Sloes are a type of British native plum. They grow on a spiky, shrubby tree known as the blackthorn (Prunus spinosa). Blackthorn grows as a self- or deliberately sown small tree in hedgerows and field boundaries, favouring long-established farmland. You’ll also find it on the fringes of moors, scrub and heathland or sometimes close to abandoned ex-industrial sites that are slowly being reclaimed by nature.

One of the main identifying features of the blackthorn is its long and vicious thorns. These two-inch spikes are very sharp and strong enough to pierce leather with ease. This is no surprise, as the tree’s thorns originally evolved as a defence mechanism to deter passing aurochs, a huge prehistoric ox that roamed the plains of ancient Britain. Early farmers would have likely taken full advantage of the shrub as an animal deterrent, putting them to use as some of the first cattle-proof fencing.

In Balkan folklore, the wood from a blackthorn tree was said to be the most effective for killing vampires. In British mythology, blackthorn blossom is said to foretell a death in the family. Although the origins of these stories are lost in the mists of time, the sharp thorns of the blackthorn do carry a particularly nasty kind of bacteria. In the past, before antibiotic treatment, stray pieces of thorn would have been a serious matter. Some unfortunate souls would have lost the use of fingers, feet, legs or arms and may have required amputation of a limb before the infection spread across their body, resulting in an untimely death. Today, a course of antibiotics and at worst a small operation to remove the thorn is all that is required, but it isn’t hard to see why mortality and the blackthorn became so closely linked.

Identification

Early to blossom, blackthorn trees have clouds of snow-white flowers in early spring. Sloes are the tree’s small, plum-like fruits. They appear as bright green marble-sized berries in mid-summer and ripen to a dark inky blue-purple colour.

Unlike other plum species such as damsons, cherry plums, domestic plums and greengages, which can all be eaten raw, sloes need to be sweetened prior to use. Anyone brave or foolish enough to try one raw will know why: they have a mouth-puckering astringent ‘flavour’ that will strip your entire mouth of moisture.

When to Pick Sloes

Sloes ripen from late summer into autumn, and the exact timing varies from year to year and from place to place. They can be ready as early as mid-August, but in some years and locations not until November. Rather than going by the calendar, go by the fruit itself.

Ripe sloes are a dark, inky blue-purple and feel soft when gently squeezed. If they’re still green or hard, leave them a while longer: for use in sloe gin, pick the sloes when they are dark and soft, and not before.

Traditionally, foragers were advised to wait until after the first frost of the year to pick sloes, so the fruits ‘bletted’, or froze and then thawed. This process ruptures the cell walls of the fruit and allows the flavour to seep out. Some sloe gin recipes also advise pricking the fruits with a pin, or even the thorn of the tree itself, which does much the same job. These days, there’s no need – you can simply pop your sloes in the freezer overnight and then allow them to thaw.

Picking sloes can be a thorny business, so come prepared. A pair of tough gloves, such as CRUD’s Dickson Gloves, made from full-grain cowhide leather with a Kevlar lining, will help protect your hands from scratches and cuts – although with thorns that can pierce leather, you’ll still want to pick with care. To carry your haul home, Barebones Living’s Waxed Canvas Gathering Bag is a handy option, with a watertight removable liner, a drop-out bottom for easy emptying and convertible straps that let you wear it across your chest or on your back.

Classic Sloe Gin Recipe

For many, a good harvest of sloes can mean only one thing: a good quantity of sloe gin. This is essentially just a sweet fruit liqueur, albeit one that is both delicious and much-loved in Britain, especially as a winter tipple. But gin is not the only spirit suitable for steeping sloes. Brandy, whisky and vodka can all complement the delicious, floral notes of this tiny plum.

No matter which spirit you decide to use (I am partial to a little sloe whisky myself), the ‘recipe’ is exactly the same and very easy to remember. Simply halve the quantity of sloes to spirit and halve the amount of sugar to fruit. So, your recipe will look something like the following:

Ingredients

• 1 litre of gin (or whisky or vodka etc.)
• 500g sloes
• 250g white caster sugar

Again, remember to pick the sloes when they are dark and soft and not before. This can be as early as mid-August and as late as November.

Method

1. Pop the sloes in the freezer overnight and allow to thaw. This will allow the flavour of the sloes to seep out.
2. Next, grab a sterilised jar or bottle and add a layer of sloes. Top with a layer of sugar and repeat.
3. Drench the fruit and sugar in the spirit of your choice.
4. Store for three months or more – the flavour will improve with age.
5. Once ready, either leave the fruits in the spirit or decant the liquid into another bottle.
6. Drink neat as a liqueur or use as you would a normal dry gin, either with tonic water or another mixer, or in any number of cocktails.

Variations on this recipe can include adding cloves, cinnamon or other spices to the mix to give an added piquancy. Of course, you don’t have to limit yourself to sloes; you can make a hedgerow gin or vodka by adding blackberries, hawthorn berries, rosehips etc. Alternatively, use the quantities in the recipe above to make cherry brandy.

Sloe Olives Recipe

Sweetening the sloe is not the only way to reduce its astringency. In many cultures, immature fruits are fermented or brined to help break them down. Most notably, the hard fruits of the olive tree are brined to soften them and remove unwanted flavours. Ripe or unripe sloes can be treated in the same way. The result is a salty, olive-like fruit with far more complex and floral notes. However, the process takes around a month, so it is not a project for the impatient. Use green or ripe sloes or try a mix of the two.

Method

1. Rinse green or ripe sloes (or a mix of the two) in clean water and pat dry.
2. Score a groove into each sloe, without piercing the pit/seed.
3. Submerge the fruits in a brine solution of 1 part salt to 10 parts water. This is best done in a Kilner-type jar.
4. After a week, rinse the sloes and resubmerge in brine.
5. Continue to change the water once a week. Check for any mould build-up on the fruits and discard any that go mouldy. Mould floating on top of the water is fine, as long as you clean and resubmerge in fresh brine. During each check, also taste for astringency. Once this has gone, the sloes are ready to eat.
6. Rinse the brined sloes, pat dry and put them in a sterilised jar.
7. Optional: Cover the sloes with olive oil and wait for a further month or so. The fruits will plump up and take on a smooth, olive-like quality.

What is a sloe?

A sloe is the small, plum-like fruit of the blackthorn (Prunus spinosa), a spiky, shrubby tree found in hedgerows and field boundaries across Britain. Sloes are a type of native British plum, ripening from bright green to a dark inky blue-purple, and they are best known as the key ingredient in sloe gin.

When are sloes ripe?

Sloes are ripe when they are dark blue-purple and soft to the touch. That can be as early as mid-August in some years and as late as November, so check the fruit rather than the calendar. Traditionally, foragers waited for the first frost before picking, but you can get the same effect by freezing your sloes overnight and letting them thaw.

Can you eat sloes raw?

You can, but we wouldn’t recommend it. Unlike damsons, cherry plums, domestic plums and greengages, sloes have a mouth-puckering, astringent flavour that strips your mouth of moisture. They’re best sweetened, as in sloe gin, or brined to make sloe olives, which helps to reduce their astringency.

How to identify sloe berries?

Look for small, marble-sized, plum-like fruits growing on a spiky, shrubby tree: the blackthorn. Sloes start out bright green in mid-summer and ripen to a dark, inky blue-purple. Blackthorn itself is recognisable by its long, sharp two-inch thorns and its clouds of snow-white flowers in early spring, and it is commonly found in hedgerows, field boundaries and on the fringes of moors, scrub and heathland.

Dave Hamilton is the author of Where the Wild Things Grow: the Foragers Guide to the Landscape, published by Hodder and Stoughton. He has led the Guardian Masterclass in foraging and currently works as an instructor for Britain’s leading foraging course company, Wild Food UK.