In a saucepan over medium heat, combine apple cider vinegar, white balsamic vinegar, water, sugar, salt, juniper berries, star anise and pickling spice.
Once the liquid comes to a boil, remove from heat and set aside.
Place chopped rhubarb in a quart jar. There is enough liquid to also use a quarter pint if you want, just distribute rhubarb in the two jars.
Pour the cooled pickling liquid over the rhubarb. Seal and storage in fridge.
Stores for two weeks.