Use a food dehydrator set at 115-125°F for 12-15 hours, stirring periodically, until completely desiccated. As an alternative, spread hips on a baking sheet in the oven using the lowest setting, around 180°F, for 6-12 hours with the oven door slightly ajar. Dried rose hips should feel completely crisp and brittle when ready to store in an airtight container.