Bottle Gentian has deep blue flowers never actually open, giving them their bottle-like appearance. The blooms are pollinated exclusively by bumblebees, which pry open the flowers to gain entry into the inner sanctum. Bottle Gentian are slow-growing but long-lived and require little care once established. Blooming late into the fall, Gentiana andrewsii seems impervious to the effects of Jack Frost. Hardy to Zones 3 - 6.