Blue gentian (Gentiana andrewsii) is sometimes called "closed bottle gentian" because of its unusual flower form.
This native of northeastern North America, from the Dakotas to the East Coast and through eastern Canada, requires the strength of a bumble bee to pry apart its bottle-shaped blue flowers. Once inside, the bee will drink nectar and collect pollen on its fuzzy body.
This plant blooms late in our growing season in Minnesota, making it an important nectar and pollen source for bumble bees still foraging in late fall. It grows in full to part sunny sites in medium-wet to medium-dry soils. Plants and seed can be purchased at native plant nurseries.