Rinse the strawberries. Place in a pot and crush coarsely. Rinse the rhubarb and cut into 1 cm (approximately 1/2 inch) pieces. Add the rhubarb, lemon juice and sugar to the pot.
Allow to sit covered for 1 hour. Bring to a boil, while stirring, and allow to cook for 3 minutes. Divide the jam between hot sanitized jars and twist on the lids. Set the jars upside down and allow to cool for 5 minutes. Turn so the lid is facing upwards and allow to cool completely. To preserve the jam for longer, you will need to process the jars according to manufacturer's instructions, or visit http://nchfp.uga.edu/.