Blueberries are round, dark blue berries that grow on bushes. They are native to northern North America, but now they are also grown in other parts of the world, such as Scandinavia. North America, however, produces nearly 95 percent of the world's crop.

There are two types of blueberries, wild and cultivated. Wild berries, which grow on low bushes, are small and sometimes tart. Cultivated blueberries, which grow on tall bushes that allow them to be cultivated by machine, are larger and generally sweeter.

A blueberry bush has a short harvest season. However, blueberries are now grown from Florida to Canada, keeping supermarkets supplied with fresh berries from May to September. If you live in an area where blueberries are grown, you will find them in abundance during their short peak season at produce and farmers' markets. Fresh blueberries are available in pints and half pints. Frozen blueberries are packaged in bags. Canned blueberries, both wild and cultivated, are packed in water or a sugar syrup.

Choose firm, plump berries with a silvery bloom. Avoid shriveled blueberries or berries with a green or red tint (an indication of an underripe berry). If the berries are packed in a clear plastic container, turn the container over and check for moldy or crushed berries. If they are packed in a paperboard container, look for juice stains on the bottom of the container, which may indicate that some berries are crushed. Crushed berries mold quickly.

1 pint blueberries = 2 cups. 1 (10-ounce) package frozen blueberries = 1-1/2 cups.

If packaged in plastic, fresh blueberries should be stored in the refrigerator in their original package. If packaged in cardboard, the blueberries should be transferred to an airtight container. Fresh berries may be kept up to ten days. Wash them just before using. Periodically check for moldy and crushed berries and discard them to prevent other berries from decaying. Fresh berries can be frozen immediately after purchasing. Before freezing, wash the berries and discard moldy, underripe and shriveled berries. Place dry blueberries in a single layer on a jelly-roll pan and freeze them until they are hard. Transfer to a freezer bag for storage. Frozen blueberries can be stored in the freezer for up to one year.

Wash fresh berries just before using, discarding moldy, underripe or shriveled berries and woody stems. Canned blueberries should be drained and dried on paper towels before using. Frozen blueberries should be added to batters while still frozen. When making pies and cobblers with frozen or canned berries, remember that these berries give off more juice during baking than fresh blueberries do. To compensate, decrease the liquid and increase the thickener when substituting frozen or canned berries for fresh berries.

To prevent blueberries from turning green in pancakes and muffins, do not use them in batters that contain baking soda.