Plants with erect, branching stems and narrow leaves produce an abundance of shallow-cupped, five-petaled flowers over a long bloom period. Each bloom lasts only a day, but others keep coming. The flax of commerce L. usitatissimumis grown for its fiber and seeds, which yield linseed oil.
Use in borders; some naturalize freely in uncultivated areas. Do best in light, well-drained soil. Most perennial kinds live only 3 or 4 years and should be replaced regularly. Easy to grow from seed; perennials also can be propagated from cuttings. Difficult to divide.
L. flavum. GOLDEN FLAX. Perennial. Zones US, MS, LS, CS; USDA 6-9. From central and southern Europe. To 1215 in. high, 1 ft. wide, with somewhat woody base. Grooved branches, green leaves. Branched clusters of golden yellow, inch-wide flowers bloom in spring and summer. 'Compactum' is just 6in. high and wide.
L. grandiflorum. FLOWERING FLAX. Annual. Zones US, MS, LS, CS, TS; USDA 6-11. From North Africa. To 12 ft. tall and 612 in. wide, with narrow, gray-green leaves. Summer flowers are rose-pink, 11 in. wide. Sow seed thickly in place in early spring or (in mild-winter climates) in fall. Self-sows without becoming a pest and is often included in wildflower mixes. Two selections are far more common than the species: 'Rubrum', scarlet flax, with bright red flowers; and 'Bright Eyes', bearing white flowers with a brownish red eye.
L. narbonense. Perennial. Zones US, MS, LS; USDA 6-8. Wiry-stemmed Mediterranean native to 2 ft. tall, 1 ft. wide. Narrow, blue-green leaves. Open clusters of 1-in., azure-blue flowers with white eye; blooms in late spring and early summer. 'Six Hills' has rich sky-blue blossoms.
L. perenne. PERENNIAL BLUE FLAX. Perennial. Zones US, MS, LS; USDA 6-8. Native from Europe to central Asia. Most vigorous blue-flowered flax, to 2 ft. tall, 1 ft. wide. Narrow, blue-green leaves; stems are usually leafless on lower part. Blooms profusely in late spring and summer, producing branching clusters of light blue flowers that close in shade or late in the day. Self-sows freely.