1. Clean the rhubarb stalks, peel and cut into small pieces.
2. Combine all the ingredients, cover and let sit overnight.
3. The next day, cook for approximately 1 hour at a low simmer until the mixture thickens.
4. Scald the jars in boiling water and turn them onto a clean kitchen towel; do not dry them.
5. Let the jam cool until lukewarm and ladle it into the jars.
6. Do not cover the jars until the jam has cooled completely. Refrigerate.

If you want to keep this jam more than 10 days, process the jars for 20 minutes in a canner full of boiling water.