Bottlebrush - Callistemon

What is a Bottlebrush?

Bottlebrushes are members of the genus Callistemon and belong to the family Myrtaceae. They are closely related to paperbark melaleucas, which also have 'bottlebrush' shaped flower spikes. It is difficult to tell to which genus some species belong. Botanists are currently closely studying these plants to determine how they are best classified. There are 40 species currently called Callistemon.

Where do they Occur?

Most Bottlebrushes occur in the east and south-east of Australia. Two species occur in the south-west of Western Australia and four species in New Caledonia. Bottlebrushes can be found growing from Australia's tropical north to the temperate south. They often grow in damp or wet conditions such as along creek beds or in areas which are prone to floods.

Bottlebrushes as Garden Plants

Bottlebrushes make excellent garden plants. Plants are all woody shrubs which range from 0.5 m to 4 m tall. The flowers can be spectacular and are irresistible to nectar-feeding birds and insects. Most species are frost tolerant. The popularity of bottlebrushes as garden plants commenced soon after European settlement and Crimson Bottlebrush (Callistemon citrinus ) was introduced to Britain by Joseph Banks in 1789. Many species can tolerate (or thrive in) damp conditions, yet most are very hardy and will tolerate drought and limited maintenance. They grow well in a wide variety of soils, except those which are highly alkaline. Plants grown in full sun produce the best flowers. Plants can be lightly pruned after flowering to keep them in shape. A low-phosphorous fertiliser should be applied in spring and autumn. Mulching will help retain soil moisture and reduce weed growth. Many cultivars have been selected from natural variants and hybrids between species. Some of these are very good garden plants.

Pruning

Generally speaking, light pruning with the genus Callistemon refers to pruning into the new seasons 'wood', that is, not cutting back into the interior of the plant where there is little or no foliage. This can take the form of:

'Tip pruning' undertaken as new growth appears (bearing in mind that the next lot of flowers are formed on the end of this growth after it has hardened and therefore you may be sacrificing some flowers if you do not do this early enough), or

pruning just behind the flowers, as they are finishing, probably the preferred option unless prior to winter when subsequent new growth may be damaged by frost.

Having said all this, you may need to sacrifice flowers for shape in the establishment stages, and on occasions older tired Callistemon may regenerate from basal pruning (all branches removed at ground level - the equivalent of a bushfire if you like). We have done this with some success at the Botanic Gardens, particularly with older plants and the result for survivors has been a tremendous & vigorous response. Additional fertiliser at the time, assists this process.

Propagation

Bottlebrushes are easily grown from seed. The unopened fruits should be collected and stored in a warm place in a paper bag until the fine seeds are released. The seed should be sown into a freely draining seed-raising mix during spring and summer.

Bottlebrushes hybridise readily so, if you wish to be sure that you are preserving the features of the parent plant do not grow plants from seed, use cuttings instead. With all cultivars it is essential to propagate from cuttings to retain the form of the parent plant. Cuttings should be taken from semi-mature wood.