If blackberries are very seedy, put part or all of them through a sieve or food mill. Measure 3 cups of prepared berries. Place in an extra large mixing bowl. Add sugar, mix well and let stand for 10 minutes, stirring occasionally. Dissolve the powdered pectin in the water, bring to a boil and boil for one minute. Add pectin to berries and sugar and stir for 3 minutes. Pour the jam into freezer containers or canning jars leaving 1/2-inch headspace. Cover container. Let stand at room temperature until set (up to 24 hours).

Freeze or refrigerate.

Yield: about 7 half-pint jars

Source: University of Georgia and USDA