When should I bring my pots of agapanthus into the shed for winter? Before or after the first frost? Also should I keep them watered during their "holiday" in the shed?
These plants are hardy down to about 20 degrees or so. Frost will not harm them, however when the temperatures drop close to unsafe levels, it would be best to bring them in. It is always good to reduce watering when over wintering, so that you do not get a fungus. Here is an article on their care: https://www.gardeningknowhow.com/ornamental/bulbs/agapanthus/agapanthus-plant-care.htm