My husband & I make jams/jellies for some local farmstands & 2 of them are strawberry rhubarb & blueberry rhubarb. We water bath them - the freezer is too filled with fruit! I make triple batches when using rhubarb but have to wait longer for it to jell, & use a little more pectin. The ratio is 2 berry to 1 rhubarb.
Terry in NY