In sauce pan over medium heat, cook rhubarb, strawberries, orange juice, and maple syrup until it comes to a boil.
Reduce heat to medium low and let simmer for about 15 minutes until fruit breaks down. Stir occasionally to keep from burning and use a potato masher to break up big chunks.
Reduce heat to low and stir in chia seeds and let simmer for another 15 minutes.
Turn heat off and let sit for 10 minutes. (Chia seeds will expand as it cools, thickening up the jam.)
Scoop jam out with a spoon -- it should slide slowly down the spoon. If not, add another tablespoon of chia seeds and let sit for another 10 minutes.
Refrigerate for up to 4 weeks or freeze in an airtight container for up to 3 months.