Family: Polemoniaceae

This genus includes around 67 species, all but one native to North America and Mexico. These annuals, perennials or alpines, with their fragrant, colourful flowers, are grown around the world for their spring to summer and autumn displays. Excellent edging and border plants, they also make attractive hanging baskets and window boxes.

Species

P. carolina, thickleaf phlox, zone 5, is an herbaceous perennial, growing to about 1 m (3 ft), with purple to pink flowers.

P. divaricata, wild Sweet William, zone 4, is a creeping, spreading perennial, rooting down as it grows. It bears lavender, violet or white flowers in early summer.

P. douglasii, zone 5, is an evergreen perennial that forms a mound about 20 cm (8 in) high, producing pink, white or lavender flowers in late spring or summer.

P. drummondii, zone 6, is the familiar, annual phlox which grows 10-40 cm (4-16 in) high, depending on variety. Numerous strains of this annual are available, most with flowers in shades of white, pink, red, purple or lavender, some with a contrasting eye.

P. paniculata, zone 4, is a popular, herbaceous perennial which grows 40-80 cm (16-32 in) high. Many cultivars are listed, but the following are some of the better known: 'Blue Boy, with mauve-blue flowers; 'Brigadier', with orange-red flowers; 'Bright Eyes', which has pale pink flowers with a red eye; 'Mia Ruys', which is pure white; and 'Prince of Orange', with dark orange blooms.

P. subulata, zone 3, may be known as alpine phlox or moss phlox. This is an evergreen perennial that may be mound- or mat-forming. It is at its best in rockeries, where it has room to spread. There are many named cultivars, the late spring or early summer flowers being pale blue, white, pink, purple or red.

Cultivation

Easily grown, phlox prefer rich, well-drained soil and plenty of water during the growing season. They need a warm, sunny situation, protected from strong wind. Feed with all-purpose fertilizer during the growing season. Propagate the perennial species from root cuttings or by lifting and dividing about every three years. Grow the annuals from seed, sown in spring once the soil has warmed, or raise in a heated greenhouse. Pinch out the growing tips of the first shoots to ensure compact, bushy growth. Regular removal of spent flowers will prolong the flowering display. Propagate the alpine species by layering or by root division. Plant in a fairly rich, moist soil in sunny, protected rockery crevices. Drainage must be excellent to avoid rotting of the roots, especially in winter.

Climate

There are species suited to various climatic zones.