The surprise of finding wild blackberries creeping along the edges of the woods is one of the great pleasures of these deep summer days. Even the mean wild vines, stretching out their vicious thorns to scratch you, cannot dim the pleasure. The purple juice stains your fingers for days, a trophy, a tattoo.
No other pie tastes quite like this one, and few are so forgiving. The most important point is to taste the berries and decide how much sugar to throw in. Some berries are large, moist, generous with sweetness while others are so small, tight and circumspect that only heat can make them sweet. Taste the berries, and then add anywhere from half a cup to a whole one for 4 to 5 cups of berries.
You can thicken this pie with anything you like; I’ve used cornstarch, instant tapioca or flour. Choose one, and use about 3 tablespoons. You can add cinnamon if you like, but I think these berries deserve to stand on their own.
Stir the sugar and the thickener into the berries, squeeze in some lemon juice and mix gently. Toss the berries into a pie crust, dot the top with butter, cover with a top crust and cut some vents. Put the pie on the bottom rack of a very hot oven (425 or so) for about 10 minutes, then turn the heat down to 375 and bake until fragrant and golden, about 45 minutes more.