The beautiful bottlebrush trees

Bottlebrushes (Callistemon spp.) are endemic to Australia where there are about 25 species. These shrubs to small trees are popularly grown as garden ornamentals for their attractive flowering bunches that look like bottle brushes. These ‘brushes’ are made up of numerous small flowers conspicuous in their long stamens, each tipped with a golden anther. The botanical name, Callistemon, comes from the Greek word kallistos (most beautiful) and stemon (stamens).

A few species of bottlebrushs have been introduced into Singapore, grown in gardens and as wayside plants. These are all with red flowers. C. citrinus or common bottlebrush has upright branches while C. viminalis or weeping bottlebrush has branches that cascade down. Both have red flowers found at the tips of branches. There are other species with yellow and green flowers. The narrow leaves of these plants contain a fragrant aromatic oil that can be detected if they are crushed between the fingers.

Bottlebrushes are excellent bird plants. Their flowers secrete copious nectar that attract sunbirds, mynas and Yellow-vented Bulbuls (Pycnonotus goiavier).
The leaves are a favourite food of the caterpillars of an unidentified butterfly or moth that in turn serve to attract birds to these trees. However, unlike sunbirds, mynas and bulbuls, the Common Ioras (Aegithina tiphia) are attracted to the plant when it is in season because of the caterpillars. The caterpillars normally congregate at the ends of branches, weaving the leaves together to form a protective cocoon. This strategy is not always full proof, as can be seen from the image (second down) where the Iora was found using it’s beak to dig into the cocoon to get at the caterpillars.

Although bottlebrush trees are not indigenous to Singapore, they have been around long enough to attract wildlife. As such more should be planted in gardens, parks and along roadsides. These plants are also attractive in their shape and colourful flowers.

Input by KC Tsang and Johnny Wee; images of bulbul, iora and caterpillar by KC and of male Purple-throated Sunbird (Nectariniua sperata) (bottom) by Johnny.