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 34 species currently called Callistemon.
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.
The flower spikes of bottlebrushes form in spring and summer and are made up of a number of individual flowers. The pollen of the flower forms on the tip of a long coloured stalk called a filament. It is these filaments which give the flower spike its colour and distinctive ‘bottlebrush’ shape. The filaments are usually yellow or red, sometimes the pollen also adds a bright yellow flush to the flower spikes.
Each flower produces a small woody fruit containing hundreds of tiny seeds. These fruits form in clusters along the stem, and are usually held on the plant for many years.
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.
- 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.
- This seed will germinate in a seed-raising mixture that drains freely. But if preserving the cultivar is the aim, then cuttings should be taken as the seeds do not grow true to the parent.
How to Care for Your Callistemons
- Callistemons do like to be fertilised, but the fertiliser used should be low in phosphorus.
- It should be applied in both spring and autumn.
- Pruning should be done once a year just after the first flush of flowers has finished.
- Only cut off the flower spikes to just behind the flower.
- The bottle brush should never be pruned deep within the tree where there is no foliage.
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