Callistemon - Growing Guide

Commonly known as ‘Bottlebrush’

Callistemon are Australian natives that belong to the myrtle family and are associated with leptospermum, eucalyptus and metrosideros. The hardiness of some species is therefore questionable and they can, more properly, be regarded as greenhouse plants.

With us C. sieberi, the ‘Alpine Bottlebrush’, has grown beside Burncoose House for generations. It is 10-12ft high and produces pale yellow flowers on short spikes in May and June. It looks hardy and definitely is. Similarly C. rigidus, the ‘Stiff Bottlebrush’, grows up to 8ft tall with dark red flowers in July to August and is perfectly hardy in frosts of up to -10°C. C. pallidus, the ‘Yellow Bottlebrush’, with its small narrow leaves and cream coloured flowers is also perfectly at home in the garden.

Callistemon sieberi

Callistemon sieberi

Callistemon rigidus

Callistemon pallidus

C. citrinus, the ‘Crimson Bottlebrush’, and its varieties are perhaps the showiest of all the bottlebrushes. The contrast between the light green leaves on the dwarf growing C. citrinus ‘Little John’ and its splendid dark red flowers makes this a perfect border shrub. C. citrinus ‘Splendour’ is perhaps the showiest of them all. However C. citrinus varieties are slightly more tender with us and need full sun and full protection from cold winds to thrive in the garden. They may be best grown as patio plants and brought into the greenhouse for the winter.

Callistemon citrinus 'Little John'

Callistemon citrinus 'Little John'

Callistemon citrinus 'Splendens'

Callistemon citrinus 'Splendens'

Callistemon citrinus 'Splendens'

Callistemon citrinus 'Red Cluster'

Callistemon viminalis

Callistemon flower best when they have basked in and been baked by the sun. Moist but well drained acid to neutral soil is therefore ideal. Under glass grow them in a loam based potting compost in full light with good ventilation. Feed with liquid feed in the growing season and top dress in the spring in colder parts of the country.

Callistemon can get out of hand under glass; C. rigidus especially, and this species may well need support. Hard or restrictive pruning will not hurt these plants at all.

Callistemon pruning

Callistemon pruning

Callistemon pruning

Callistemon pruning

Callistemon pruning

Callistemon seeds

Bottlebrushes produce clusters of tough spherical seeds which hold on the stems for several years. These remain viable and can be sown on the surface in moist compost in spring. Semi-ripe new growth cuttings can however also readily be taken in late summer.