Callistemon: Greenhouse Plants
FF – frost free only
Australia and Tasmania
In some areas these somewhat unruly shrubs can be grown outside but are never reliably hardy. However, as a plant for the frost free collection they can be rewarding, producing fluffy spikes of red, yellow, white or green flowers lending them the name of Bottle-Brush. The stamens form the main part of the flower. The showiest is probably Callistemon citrinus, in particular C. c. ‘Splendens’, the red ‘brushes’ of which are 10 cm (4 in) long. It has the added attraction of a delicious lemon scent when the leaves are crushed. C. salignus has yellow flowers and there is a white form C. s. ‘Albus’. C. pinifolius has unusual yellow-green flowers.
The problem with these is their eventual height and straggly habit. Pruning should consist of cutting back straggly growths hard in autumn. This should never be done unnecessarily, as after a plant has flowered the shoot grows beyond the dead flower to produce the wood which will flower the following year. A really badly shaped plant could be cut right back but it may not flower for a year after this. They need good light to flower well and, in common with most Australian plants, prefer a well-drained loam-based. Should they require potting, this should be done in the spring. Propagation is by 8-10-cm (3-4-in), preferably heeled rooted in a temperature of 15-18°C (60-65°F). Seed should be surface sown and stood in a light place at 13-18°C (55-65°F). Plants can take four or five years to flower from seed.