Description from Flora of China
Callistemon R. Brown; Kajuputi Adanson.
Trees or shrubs. Leaves alternate or opposite-decussate, petiolate or sessile; leaf blade leathery, secondary veins basal and parallel to leaf axis or pinnate. Flowers bisexual or female sterile, arranged in spikes or heads and pseudoterminal or lateral. Hypanthium subglobose or campanulate. Sepals 5, caducous or persistent. Petals 5. Stamens numerous, greenish white; filaments basally connate into 5 bundles opposite petals; anthers dorsifixed, cells parallel, dehiscing longitudinally. Ovary slightly adnate to hypanthium, 3-loculed, apex prominent; ovules numerous. Style linear; stigma ± enlarged. Capsule semiglobose to globose, apically dehiscing. Seeds obovoid-oblong to obovoid; testa thin; embryo straight.
Callistemon is to be included in Melaleuca as the two genera overlap in many morphological aspects. Several species are occasionally cultivated in China under Callistemon, including C. citrinus (Curtis) Skeels (C. lanceolatus Candolle), C. linearis (Smith) Candolle (C. rigidus R. Brown), C. rugulosus (Schlechtendal ex Link) Candolle (C. coccineus F. Mueller), C. salignus (Smith) Colvill ex Sweet, and C. viminalis (Solander ex Gaertner) G. Don ex Loudon. The cultivated species treated under the name M. parviflora Lindley in FRPS (53(1): 55. 1984) is not that species; no material has been seen and its true identity is unknown.
About 280 species: mainly in Australia, but also in Indonesia, New Caledonia, and Papua New Guinea; several species cultivated in China but only one commonly cultivated.