Every year, I pull my geraniums out of the soil in fall and store them in cardboard boxes in the basement until February. I sprinkle the roots a few times over the winter. By February they have started to form leaves and I then pot them up and keep them in a sunny window until it is warm enough to put them outside. I usually cut them back when potting them, so they don’t get tall and gangly . But is this right? Should I be cutting them back when I put them in the boxes in the fall, instead?
You are doing everything just right! And the proof is that you have done this successfully year after year. Some people store the pulled up geraniums hanging upside down in paper sacks, but it seems the cardboard box method is working well for you.
One reason why it is good to wait before cutting back is so you can see any stems that have shriveled and died over the winter and thus, you are tidying up your plants as well as shortening them.