Family: Rubiaceae

From tropical Africa and Madagascar, this genus includes around 30 species of perennials and shnibs with opposite leaves and clusters of attractive, delightfully coloured flowers. In frost-prone climates they make good pot plants in an intermediate greenhouse or conservatory.

Species

P. bussei, red star cluster, is rather straggly, with ribbed, ovate leaves and scarlet, spring flowers, and grows to 1 m (3 ft) or more.

P. lanceolata, Egyptian star cluster, is a compact shrub to 2 m (6 ft) tall, from the Arabian peninsula to tropical east Africa. It makes a good greenhouse pot plant and in warm climates can be bedded out for the summer. It is grown for the bright green, hairy, oval leaves and large clusters of starry flowers, in pink, lilac, purple or magenta, which bloom for months. Many varieties are available, some with two-toned flowers.

Cultivation

Under glass, grow in soil-based potting compost with extra grit added. Give good light but shade plants from direct sun. Prune in late winter to restrict size, if necessary. Remove dead flower heads regularly. Propagate from softwood cuttings all year round and root them in a heated propagating case.

Climate

Warmest parts of zone 10 to tropical.