Offering some of the richest blues in the garden, these delightful, refined plants are considered by many to be difficult customersand some of the rock-garden types are indeed pretty finicky. All of the species listed here, however, are easy to grow if planted in moist, acid soil enriched with plenty of organic matter. Most are best suited to the Upper and Middle South and the higher elevations of the Appalachians, Blue Ridge Mountains, and Ozarks, but some can also be grown as far south as Mississippi and Alabama. Do not disturb plants once they're established.
G. andrewsii. BOTTLE GENTIAN. Zones US, MS; USDA 6-7. A legendary wildflower of the eastern U.S. To 2 ft. tall and less than half as wide, with erect, unbranched stems set with paired, dark green, 2- to 3-in.-long leaves. Clusters of 2-in.-long, deep blue flowers appear atop the plant in autumn. Blossoms never open completely, so they have a distinctive bottle shape. Often the last wildflower to bloom in fall. Does well in soil that is constantly moist or even boggy; perfect along the edge of a stream or pond. A white-flowering form is available.
G. asclepiadea. WILLOW GENTIAN. Zones US, MS, LS; USDA 6-8. Native to Europe and western Asia. Forms a clump of arching stems to 2 ft. tall, 112 ft. wide. Dark green, 2- to 3-in.-long leaves. Blooms in late summer and early fall, with deep blue blossoms appearing singly or in twos or threes in joints of upper leaves; flowers are 112 in. wide and open into a star shape. Give regular water and well-drained soil. 'Rosea' has pink blooms.
G. clausa. CLOSED GENTIAN. Zones US, MS; USDA 6-8. Native to eastern U.S. Very similar to G. andrewsii, but the flowers are slightly larger and have white showing around the edges of the petals. Give same conditions as G. andrewsii.
G. saponaria. SOAPWORT GENTIAN, HARVESTBELLS. Zones US, MS, LS, CS; USDA 6-9. Native to eastern and southern U.S. Slender, erect stems to 2 ft. tall, with medium green, broadly lance-shaped leaves to 312 in. long. Clusters of light blue, closed, cigar-shaped flowers to 112 in. long appear in fall. Does well with regular to ample water; best in moist, rich, well-drained soil but tolerates boggy conditions.
G. septemfida. SUMMER GENTIAN. Zones US, MS, LS, CS; USDA 6-9. From Caucasus, Turkey, and Iran to central Asia. Arching or sprawling stems 918 in. long form a spreading mass about 8 in. high, 1 ft. wide. Medium green, oval leaves to 112 in. long. Clusters of 2-in., dark blue flowers in late summer. Easy to grow if given regular water and rich, well-drained soil. Good choice in rock gardens; tolerates a bit more sun than other species listed. G. s. lagodechiana, the form commonly sold, is similar but has more widely spaced flowers.