Callistemon genus

(Bottlebrush)

Despite the undignified common name, callistemons are a favourite garden plant, and not just one of Australia's favourite garden plants either. Some species have become favourite plants in other parts of the world too.

In fact, this photograph of a Callistemon citrinus is growing in France (courtesy of http://www.aujardin.info ). And a Google search of Callistemon will find them discussed on websites all over the world, including the UK, Ireland and the USA.

Most are woody shrubs but one or two can be categorized as small trees, such as C. viminalis (Weeping Bottlebrush), as shown in the photograph below, which can grow up to 6 metres tall.

Callistemons come in a variety of shapes and leaf forms too, but those distinctive bottlebrush flowers remain their most readily identifiable feature. Flower colour varies from the more common red through to mauve, pink, cream and green. Many species have two flowering periods a year. And of course birds just love callistemons, so they are a good addition to a wildlife-attracting garden.

Generally, most Callistemon species tolerate a wide variety of soil types, from the most poorly drained soils through to sandy soil. They often tolerate a wide variety of conditions too, including coastal locations, but this does vary between species and cultivars.

For good flowering, all callistemons require full sun.

Propagation

Callistemons grow very easily from seed, which should be collected from older wood to ensure maturity. Cuttings can also be taken of most species and they strike very readily. To ensure the plant is a clone of the parent plant, cuttings need to be used. Seed grown plants can vary substantially from the parent.

A Selection of Bottlebrushes

C. citrinus This species can also be a small tree, growing to 6 metres in height, with quite a stiff form. It's certainly the most common Callistemon and many cultivars (including white forms) have been developed from this species. It's hardy and even tolerates very wet conditions. Does best with regular pruning and light fertilising after flowering (which it does in late spring, summer and autumn).

C. comboyensis This is a spreading shrub that can grow to 4 metres in height and about 2 metres wide, although it seldom does grow this large. The coppery coloured new leaf growth is quite a feature as well as the red flower spikes which appear in summer and autumn. It's hardy in most soils but does need a sunny position.

C. 'King's Park Special' Although this plant was discovered growing in King's Park in Perth, the parents are probably eastern states species. It grows to about 4 metres tall and forms a naturally rounded shape. It produces masses of flowers as multiple heads of crimson spikes during spring and summer. (Image courtesy of Australian National Botanic Garden.)

C. 'Little John' Often described as a rockery plant because of its smaller compact form, 'Little John' is one of the hardiest cultivars. It tolerates heavy clay or sandy soils, second line coastal, even temporary inundation, and it's frost tolerant. The compact bottlebrush flowers are produced in spring and summer. This cultivar does well in containers too.

C. 'Mauve Mist' Mauve-pink flower spikes, which are produced in clusters during summer, have guaranteed this cultivar's success. It's a dense shrub that will grow to about 3 metres tall and 3 metres wide.

C. pachyphyllus - green form This small Callistemon grows to about 1.5 metres in height and width and produces red or sometimes green flowers in spring, summer and autumn. To ensure the same flower colour, cuttings need to be taken of this plant and not grown from seed. It tolerates very bad drainage but demands full sun.

C. salignus This one is definitely a small tree, growing to 9 metres in height. It has papery bark, so it can be mistaken for a Melaleuca at a glance. It flowers during summer and the bottlebrushes are mostly cream coloured. The foliage is particularly attractive, especially the new leaf growth which is a pinkish colour. It is very hardy, tolerating most soil types and even grows well in coastal areas, but it does require ample water.

C. viminalis This is a favourite Callistemon because of its naturally weeping habit and a number of cultivars have been developed from it. It can grow to 6 metres tall so it can also be categorized as a small tree. The bright red flower spikes occur in summer and autumn and can be 9cm in length. It is an outstanding landscape plant and a great screen plant. This is one species that is well-established overseas, although it is borderline for frost tolerance.

Information sources:
Wrigley, J.W. & Fagg, M.,2003, Fifth Edition, Australian Native Plants, published by New Holland Publishers.
Peate, N., MacDonald, G., & Talbot, A., 2006, Third Edition, Grow What Where, published by Bloomings Books.
Australian Plants Society
farrer.csu.edu.au

Other recommended text for more detailed information:
Wrigley, J.W. & Fagg, M., 1993, Bottlebrushes, Paperbarks and Tea Trees, published by Angus & Rovertson.

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