One method for preserving rhubarb and strawberries is to make a jam or compote. After making the jam or compote, store the preserves in sanitized glass jars.
To make strawberry compote, wash and hull 2 cups fresh strawberries. Chop enough rhubarb stalks to make 2 cups, about 1 1/2 pounds.
Combine the strawberries and rhubarb in a medium pot. Add 3/4 cup sugar, and cook over low heat, stirring constantly until the sugar dissolves. Keep cooking and stirring until the mixture is the consistency of applesauce. Remove from heat, and taste for desired sweetness.
To make jam, prepare 4 1/2 cups of each fruit the same way. Place the rhubarb and 6 cups sugar in a heavy pot, and let it stand for two hours. Stir in 1/4 cup lemon juice, and add the strawberries.
While stirring, bring the mixture to a boil, and then reduce the heat to medium-high. Keep cooking at a rolling boil for 20 to 25 minutes or until the mixture thickens. Remove from heat, and stir for two minutes. Skim off any foam.
To preserve the compote or jam, pour it into clean canning jars. Tap the bottoms to release any air bubbles, and wipe the rims. Screw on the canning lids, and submerge the jars in boiling water for 10 minutes.