gentiane à tiges rouges

The closed gentian or bottle gentian (Gentiana andrewsii) is a striking herbaceous perennial in the family Gentianaceae native to eastern and central North America, found from Quebec and New England west to Nebraska and south to Georgia. Unlike most gentians, the deep violet-blue flowers of this species remain permanently closed — the petals fused into a bottle-like shape through which only strong bumblebees, primarily Bombus species, can force entry to access nectar and pollen, making it a specialist of bumblebee pollination. Plants grow 30–60 cm tall in moist prairies, wet meadows, fens, stream banks, and open woodland edges, flowering in late summer and autumn when few other wildflowers are in bloom. The closed flower form prevents small insects from accessing floral rewards while selecting for robust, strong-flying pollinators capable of forcing the petals apart. Closed gentian is declining across its range due to loss of moist prairie and fen habitats, wetland drainage, invasive species competition, and the regional decline of specialist bumblebee pollinators, with which its reproductive success is closely linked.