There are a number of native Gentiana species that qualify as "bottle" gentians, where the flowers barely open or don't appear to open at all.
After all of the heat and drought this 2010 summer in New England can dish out, I've observed the slow development of Gentiana clausa alba, unperturbed by the drought, surprising when this bottle gentian is reportedly found in moist locations and stream-sides. The foliage remained dark green, not showing any sign of scorching as so many of my plants have this season. Last year I received a seedling plant from George Newman who specializes in native North American plants, and I believe this rare white form was from seed collected in New Hampshire... I'll have to ask George, he has an encyclopedic memory with details of all the plants in his fascinating garden. Fascinating too, is that the flower bracts on G. clausa appear well before the buds, making an intriguing and curious looking posy nested on top of the enlarged terminal leaves. I like that the flowers are tinged green at the apex. I include some links showing other colors forms, the more typical blues and purples. My plant is 12" (30 cm) in flower.
Gentiana clausa - bottle gentian, blind gentian, closed gentian
USDA plant profile & distribution map