Q.Is my Columbine dead?
Last year, I bought some Columbine seeds and planted them in a fixed windowbox. The plant grew very quickly, but produced no flowers. Then, in late October, it turned brown and the leaves shriveled, but did not fall off. It has been that way ever since. Granted, it has been a brutally bad winter and I did not cover the soil with straw.
Your Columbine will grow up from the roots, if still alive, you should start seeing the leaves form at the soil level. Since it's in a container you will need to provide water.
Columbine growing in containers may be difficult. They would be happiest in ground.
Half of mine made it through our cold winter here. I'm zone 4.
Columbine is a biennial plant that does not flower until its second year. Columbines typically go dormant in the fall around October and their spring blooming is somewhat delayed compared to other plants, so this may just be a matter of having some patience. However, we can't ignore the fact that perhaps your columbine suffered a serious cold injury, but let's be optimistic! For information on how to save cold damaged plants, please visit the following article (I would follow the recommendation for watering and fertilizing):
https://www.gardeningknowhow.com/plant-problems/environmental/tips-for-saving-cold-damaged-plants.htm
When columbines go dormant and the leaves turn brown & dry like yours did, it's best to give it a "dead leafing" and take off all the foliage to keep the plant from looking too unsightly.