Almost any sort of blackberry works for this jelly, but boysenberries, loganberries, Marionberries, and olallieberries work especially well. One form of blackberry or another is in season from June through mid-September. No water is added to this pure-berry jelly, and there is just enough sugar to firm it up. Please read About Making Jelly and How to Process.

Wash and drain, then thoroughly crush in a large heavy saucepan:

Bring to a boil, stirring to prevent sticking. Cover, reduce the heat, and simmer until soupy, about 10 minutes, mashing frequently. Extract the juice. While the juice drains, prepare a water-bath canner, gather all your canning equipment, put a couple of saucers in the freezer, and have ready 3 sterilized hot half-pint jars.

Measure the strained juice, transfer to a large saucepan, and add:

Bring to a boil and cook over high heat, stirring frequently, until the mixture reaches the jelling point. Remove the jelly from the heat and skim off any foam. Pour into the prepared jars, leaving ¼ inch headspace. Wipe the rims. Place lids on jars and screw on rings until fingertip-tight. Process for 5 minutes. Let cool completely and store as directed.