We overwintered our geraniums dormant in our dark basement.
Here’s how: Storing your geraniums dormant.
When we brought the geraniums up this spring, we didn’t take them outside right away. We were afraid too much sun, too soon, might harm them. We kept them in our garage for 2 days to acclimate to the sun that came through those windows. Then we brought the geraniums outside and sheltered them next to the wooden fence.
One of the 12 geraniums we brought inside for the winter was overwatered during our acclimation process. It turned mushy. But even so, 11 geraniums is a good start on summer flowers.