Attila Kapitany is best known for his seasonally psychedelic carpets of succulents but he is under the spell of bottle trees too. At his Narre Warren North garden he has more than 100 of these squat, fat curiosities rising up from unorthodox tumbles of aeoniums, sedums, aloes, Carpobrotus and the like.
Most are the Queensland bottle tree, or Brachychiton rupestris but he also cultivates nine other types of trees with bottle-shaped trunks. Sometimes the bark is green and thorny, as with his South American Ceiba species or grey-green, as with the Brachychiton compactus, which, like the B. rupestris, is endemic to Queensland, or the whole trunk is especially short and swollen, such as B. australis, again from Queensland.
In every case the "bottle" houses a fleshy centre with a water-storing capacity that sets these trees apart from regular woody-trunked trees and allows them to survive lengthy dry spells. Kapitany says he first fell for these horticultural "oddities" more than 40 years ago and now considers them "the bees' knees".
Other people do too, with the robust B. rupestris now regularly appearing in public and private landscapes. This tree's growing popularity is at least partly thanks to the dramatic plantings of huge-bellied specimens in high-profile places such as the Children's Garden and the Volcano at the Royal Botanic Gardens, Melbourne.
Kapitany says there is no other tree with "as much trunk or stem character as a bottle tree". He says people don't fall for their leaves, flowers or fruits so much as for the trunk, which "appears like a fantasy out of Alice in Wonderland".
He says it usually takes between seven and 10 years for the bulge of B. rupestris sowed from seed to form. But there is a wide variation of growth rates within the species and also depending on how the tree is cultivated. While B. rupestris stands up to a wide variety of soil types, including clay, it grows fastest in a humus-rich, well-draining spot.
You can see the impacts of different soil types and drainage in Kapitany's garden, where Queensland bottle trees are growing on the tops, sides and bottoms of clay mounds, in compost heaps, in granitic sand, in a vegetable bed and elsewhere. The trees with the best drainage are always the biggest.
Mostly evergreen, the B. rupestris is drought-hardy and moderately frost-hardy and, while it can become more than 20 metres tall in the wild, in cultivation it often reaches less than five metres. This means it can be used in small courtyards, large gardens and as a street tree. While Queensland bottle trees can also be pruned, Kapitany warns that this is "not for the fainthearted" and that you do need to be careful about the timing and positioning of any cuts because of a risk of rot.
Kapitany also has the semi-shade-loving B. compactus growing in numerous spots in his garden as well as other bottle-shaped Brachychiton species but says they are all more temperamental than rupestris. He credits Rudolf Schulz, who began growing B. rupestris plantations in the 1980s, as being the first to see the potential of the Queensland bottle tree. While Schulz has since moved to New Zealand, the trees he planted (now with wondrously swollen trunks) are still being sold in Victoria for many thousands of dollars.
By contrast the compelling but unrelated, boab tree (Adansonia gregorii), from the Kimberley region of Western Australia, extending into the Northern Territory, struggles in climates that are different from its natural (either hot and dry or hot and humid) range. Kapitany says the only successful plantings of these iconic trees are in its home states.
But they can be appreciated from afar and one of the aims of Kapitany's talk is to get more of us seeing just how "fun and worthwhile" bottle trees can be.
Attila Kapitany will speak about boabs and bottle trees at the Royal Botanic Gardens, Cranbourne, June 17, 2pm. The talk, hosted by the Cranbourne Friends, costs $25/$20 members/$10 students. Kapitany will also give a talk – at 11am – on Australian succulents. Go to rbgfriendscranbourne.org.au to make a booking for either talk.