Gentiana andrewsii aka Closed Gentian

Gentiana andrewsii belongs to the gentian family, Gentianaceae. It is a perennial, which means it lives for years. Gardeners call it bottle gentian or closed gentian. It grows wild in south-central Canada and northern and eastern America. Kew includes Colorado in its native range, too. It grows in moist woods and low ground near water. It also grows in meadows, damp prairies, and thickets. It is native to the Midwest, but not Britain or Ireland.

In gardens, plants reach 1–2 feet (0.3–0.61 metres) tall. They spread about 1 foot (0.3 metres) wide. They form low mounds rather than woody shrubs. The leaves range from oval to lance-shaped, with parallel veins. Each leaf can reach about 0.33 feet (0.1 metres) long. Plants can form large clumps when good conditions last. Missouri Botanical Garden says leaving them alone helps this growth.

The deep blue flowers have a shape like a bottle. Their petals stay closed, hence both main common names. Tight groups of flowers grow at the stem tips. Some grow where the upper leaves meet the stems. Chicago Botanic Garden lists blue and purple flowers. It gives a bloom season of September through October. Missouri Botanical Garden gives October for the St. Louis area. Its broader account says late summer and early autumn.

Grow this gentian in part shade with moist, rich soil. It prefers cool ground rich in humus, with an acidic pH. The soil must stay moist but let excess water drain. Hot, humid climates may limit its growth. Both botanic gardens place it in USDA zones 3–7. Missouri Botanical Garden rates its water needs as medium. It says the plant needs little care and tolerates clay soil. Deer tend to leave it alone. This helps where deer eat garden plants. That garden reports no major insect or disease problems.

Bottle gentian suits woodland gardens, shaded borders, and native plant beds. It also fits shaded rock gardens and stream or pond edges. Its late flowers add colour to these sites. Plants For A Future reports no known edible uses or hazards. This does not mean that it is safe to eat. That source notes past root use for pain and headaches. It also notes eye washes and a claimed snakebite remedy. These past uses do not prove that the treatments work. It lists no other uses and no weed potential.