Blackberry pie is pie

Pie

A pie is a baked dish which is usually made of a pastry dough casing that covers or completely contains a filling of various sweet or savoury ingredients....

 composed of blackberry

Blackberry

The blackberry is an edible fruit produced by any of several species in the Rubus genus of the Rosaceae family. The fruit is not a true berry; botanically it is termed an aggregate fruit, composed of small drupelets. The plants typically have biennial canes and perennial roots. Blackberries and...

 filling, usually in the form of either blackberry jam, actual blackberries themselves, or some combination thereof. Blackberry pie is quite tart requiring far more sugar than blueberry pie

Blueberry pie

Blueberry pie is a sweet pie filled with blueberries. Blueberry pie was first eaten by early American settlers and remains a popular dessert in the United States and around the world. Blueberry pie made with wild Maine blueberries is the official state dessert of the U.S. state of Maine....

. Blackberries can be stewed or soaked in water prior to baking to prevent burning, a concern not present in preparing blueberry pie.