Rhubarb Berry Jam

2 pounds rhubarb, washed, trimmed and chopped into 1/2 inch pieces
1 pint raspberries
2 quarts strawberries, hulled and quartered
1 cup apple juice
Juice of 1/2 lemon
3 cups granulated sugar
Pinch salt

Combine rhubarb, berries and apple juice in a large pot. Set over medium heat, cover and cook, stirring occasionally to prevent scorching, until fruit is very tender, about 15 minutes. Stir in lemon juice, sugar and salt. Cook, uncovered, skimming off any of the scum that rises to the surface, until the jam is thickens and registers approximately 220F on a candy thermometer. You can test jam for doneness by spooning a small amount of jam on a frozen plate -place in freezer for a few minutes then check to see if set. Jam will wrinkle when pushed if set. Ladle jam into clean jars. Let cool completely, cover and store in the refrigerator. In theory the jam will keep for a few weeks however in practice it is usually gone in a few days. Spoon over toast, yogurt, ice cream etc.