Hybridises with :
Cherry Plum (Prunus cerasifera) Trees to produce Prunus × simmleri (which has no common name).
Wild Plum (Prunus domestica) Trees to produce Prunus × fruticans (which also has no common name).
Distinguishing Feature : The marble-sized, rock-hard, bitter, steely-blue-bloomed blackish berries which appear rather later later autumn. The scratches on hands and arms inflicted whilst trying to pick them.
Not to be confused with:
Buckthorn or Sea-Buckthorn [shrubs or trees with similar names].
Some similarities to:
Bullace otherwise known as
Damson (Prunus domestica subsp. institia), but that has not got long thorns, and the fruit (damson) is both larger and softer than are sloes.
The flowers emerge before the leaves, in late March, two weeks after Cherry Plum and a month before Hawthorn. The black berries which appear in September have a steely blue bloom that is removed on handling. The 'spinosa' part of the binomial name (the specific epithet) refers to the sharp spines on the branches.
The berries are far too bitter (and hard!) to eat, and are best left in a bottle of gin for a year with a little sugar to taste, then removed before drinking. Bletted berries make for a better sloe gin, that is, it is best not to pick them until after the first frosts (although, with warming Winters, this might be never). If there is no natural frost, bletting can be performed by cycling them alternately in a freezer and refridgerator for a fortnight before pricking the sloes and pickling them in gin. Remove and discard the berries before drinking, they are too bitter, but can be used to make a (gin-flavoured) jam afterwards.
The Blackthorn thicket is almost impenetrable and is used as hedging especially around the lanes backing on to farmers fields constraining livestock (it is a little untidy for garden hedges).
The fruits are characterised by a high concentration of phenolic acids (such as Gallic Acid), which explains their high bitterness, although other phenolic compounds will also contribute, such as flavonoids and anthocyanins. Altogether, they contain 2 coumarins, 3 phenolic acids, 6 flavonols and 14 flavan-3-ols.
Both a blue and a permanent red dye can be obtained from the berries and were used to dye wool and as an indelible ink for writing. The fruits contain several anthocyanins and anthocyanidins such as
Peonidin-3-O-Glucoside, and it will be these that are responsible for the dark blue-black colour of the berries.