The blackberry has been foraged and enjoyed for a very long time, at least 8,000 years according to the archaeological evidence. They are more highly prized in western Europe than anywhere else in the world, and collected and eaten most enthusiastically of all in Britain, where blackberrying occupies a special cultural niche as a uniquely rewarding leisure activity.
There are now as many as 2,000 varieties of Rubus fruticosus worldwide, if you count the naturally occurring hybrids and commercial cultivars, and none of them produce true berries. Instead, they are "aggregate fruits", agglomerations of individual berries known as drupelets.
The family also includes raspberries, and it's more difficult than you might think to tell the two apart. There are black raspberries and red blackberries, and the only way to be certain is to pick one; the blackberry will come away with the hard centre, or receptacle, retained within the fruit whereas that of the raspberry will be left behind on the plant. The only thing to do then is to eat the berry, and then conduct the experiment again, repeatable results being the cornerstone of empirical scientific research.
In the early season, with cream and a little sugar, the still slightly tart berries make a pleasant change from strawberries. As the fruits swell and ripen into September their sweetness becomes more pronounced and they find other homes in pies, crumbles and cobblers, frequently combined with early apples for a taste which is the embodiment of the changing seasons.
There is traditionally a date after which the berries should not be picked, most commonly taken to be Michaelmas (29 September) but later in some areas, after which time the devil is said to spit or stamp (or worse) on the berries, rendering them unfit. It seems likely that this is a reference to the grey botrytis cinerea mould which envelops the fruits later in the season. No mention in folklore is made of the more prosaic problems associated with low hanging fruit in areas where dogs are walked and child pickers roam.
According to Lia Leendertz, Loch Ness is extremely popular because it "produces a high yield from thornless, compact plants - perfect for small gardens. Alternatively, the vigorous Ashton Cross produces vast crops with a proper wild blackberry flavour. But Kotata, with its beautiful long, black glossy berries, perhaps boasts the best flavour of all."
If your style is to go no further than your own patch when foraging see here for more information on growing your own blackberries.
What to look for
The prize berry for flavour, size and ripeness is the one at the extremity of the bunch, and it's a sure sign that someone else has beaten you to the bush if they've vanished by the time you arrive. A glossy black swollen appearance indicates a ripe berry; if insects have been at the fruit it will tend to appear deflated. For more on the finer points of foraging from acclaimed expert John Wright, see here.
A good source of vitamin C, and also dietary fibre in the multitudinous tiny seeds. They also contain a mild analgesic in the form of salicylates; useful in combating the effects of an autumnal sore throat, but potentially less helpful to people with an allergy to asprin.
August to mid-October.
It's a rare person indeed who can contemplate storing blackberries. Fresh, they will not keep even overnight without losing taste and condition, and that's without factoring in the most notorious predator of the picked blackberry; the forager's own family. They do freeze very well, though, making a glut a nice problem to have. As with other soft fruit, spread them in a single layer on a tray and freeze them before transferring to a container, or simmer them briefly and freeze or refrigerate the resulting purée for a couple of days.
Stew briefly with a little lemon juice and / or sugar to taste.
Goes with / good in
As noted, blackberries and apples are best friends forever, and blackberries also lend themselves to jelly, jam, compote, tart, pie, iced desserts, syrup, liqueur and ratafia.