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Wednesday, 13 September 2017

The new Australian display

By Helen Roberts

The newly established Australian display is thriving at the University of Bristol Botanic Garden. This new area has been developed over the last year few years with the aim of introducing visitors to the captivating flora from the Mediterranean climatic region of Western and Southern Australia. The new display is part of the strategic plan for the Garden and follows on from the creation of the Mediterranean and southwest South Africa zones (N Wray 2017, personal communication, 27th July). 

The Australian display still under development
at the Botanic Garden.
This display aims to broadly showcase some of the hardier plants of Western and Southern Australia but also concentrates on the highly diverse flora of the "Kwongan", one of a number of special habitats that make up the Southwest Australia ecoregion. This ecoregion is acknowledged worldwide as one of the world’s most important biodiversity hotspots. 

Kwongan is the aboriginal term used for the mixed waxy leaved shrubland and heathland assemblage found in the southwest of Western Australia and South Australia around Adelaide. The Kwongan is comparable to the other types of shrubland and heathlands plant communities with a Mediterranean climate, such as South Africa’s fynbos, California’s chaparral, France’s maquis and Chile’s matorral. The Kwongan sandy soils are impoverished of nutrients and the climate, with its winter rain and summer droughts, has meant plants have evolved some extraordinary adaptations and survival tricks to cope with the difficult conditions. Theses plant communities display high levels of species diversity and a number of rare species not found anywhere else. 

There are many important plant families that make up the Kwongan, including the eucalyptus tree species from the myrtle family (Myrtaceae). However, the aim of the display is not to create a landscape dominated by these trees but to highlight some of the fascinating shrubs and subshrubs. A small winding path enables visitors to get up close and personal to some of these plants and be immersed in the wonderful fragrance emitted from the vegetation. Firstly, the Callistemon (bottle brushes) were planted from the Myrtaceae family, including the weeping bottle brush (Callistemon viminalis), a beautiful arching shrub with deep red bottle brush flowers. The name refers to the beautiful flowers, ‘calli’ coming from the Greek word meaning beautiful and ‘stemon’ meaning stamen, the male part of a flower. 

Banksia in bloom.
Photo credit: Shannon Martin
via Flickr [CC by 2.0]
The other important families for this display include the unusual plant family called the Proteaceae, which contains Banksia, Dryandra, Hakea, Isopogon and Grevillea. Many of these species are only found in the Mediterranean climatic region of Western and Southern Australia. All have exquisitely striking flowers and sculptural foliage. The Banksias are particularly interesting though. The flower heads are composed of hundreds of tiny flowers ranging in colour from yellow through to red. The fruits look like cones, with the seed encased to protect against seed eaters. These cone-like structures are what is termed serotinous where seed is let loose in response to an environmental trigger, which in Banksia’s case is fire or extreme drought. 

Other beautiful flowering shrubs that have been included in this attractive display are the kangaroo paws, Anigozanthos, whose flowers do vaguely resemble the paws of marsupials. The flowers themselves are vibrant and extremely eye-catching, held up on long tall stems to be pollinated by birds. The flower is arranged so that pollen is deposited on the heads of nectar feeding birds, with different Anigozanthos species leaving pollen on different parts of the birds’ head.

This new display has been intentionally placed adjacent to the southwestern South Africa display. The two continents were once connected forming the supercontinent Gondwana some 200 million years ago. In both countries, species from the Proteaceae and Myrtaceae are represented. This area of the garden is set to be further developed through a strategic plan to include five main plant assemblages of the Mediterranean climatic region. Three have now been accomplished. Next to look forward to are the plant assemblages from Central Chile and Western California. 

Helen Roberts is a trained landscape architect with a background in plant sciences. She is a probationary member of the Garden Media Guild and a regular contributor to the University of Bristol Botanic Garden blog.