Bottletrees can grow in cool climate

Brachychiton diversifiolius. Photo: Christine O'Connor.
Brachychiton diversifiolius. Photo: Christine O'Connor.
Most of Australia has a tropical climate, but a huge range of trees that we can grow outside, even in our cooler, temperate weather. These trees can give an exotic feel to our gardens, even when summer does not come to fruition.

One such tree is Brachychiton or, as it is more commonly known, kurrajong or bottletree. There are 30 native species in Australia and one in New Guinea but only a few are available commercially. Fossils of the genus have been found in New Zealand, dating back to 50million years ago, but no live specimens exist here today.

One of the most noteworthy characteristics of the plant is that several species form stout swollen trunks, making them look like an enlarged bonsai. This is an adaption to hot dry summers and is a means of storing water. Some have gone even further and become dry-season deciduous. Many of them also have outstanding displays of flowers, but this should not be relied upon, as it can be erratic. At Dunedin Botanic Garden none have flowered in the past 10 years, probably due to the lack of consistently hot, dry summers.

Several species are growing in the Australian borders of the Geographic Plant Collection at the Botanic Garden. Located above the aviary, they receive maximum light and heat, with relatively few frosts. They are very drought-tolerant but also slow growing in our climate, so patience is needed.

- Dylan Norfield is the collection curator of the Geographic Collection and Arboretum at Dunedin Botanic Garden.

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