Botanic Gardens Trust, Sydney, Australia

Australian Botanic Garden

Diversity Wall

Self-guided tour - available soon as smartphone app


Click on map to see location of the Diversity Wall


Plants of Australia’s inland are adapted to extreme conditions: scorching heat, dry winds, drought, flood and fire. The Queensland bottle tree, Brachychiton rupestris, sheds its leaves in times of drought to conserve moisture. It can survive for years with no rainfall, using water stored in its trunk and limbs.


This juvenile Queensland bottle tree, Brachychiton rupestris, is beginning to develop its distinctive bottle-shaped trunk.


Algae grow almost everywhere where water is found - from oceans, lakes and rivers to thermal springs, snow and soil, and even inside other plants, fungi and animals. There is thought to be more than 72,000 species, ranging from 65-metre-long giant kelps to microscopic single-celled protophyta. Algae are vital to the survival of life on earth; marine algae, including seaweeds, produce up to 70 per cent of the oxygen in the atmosphere and store a quarter of the world’s carbon.



The Reverend William Walter Watts (1856-1920) was a keen amateur collector of cryptogams - including ferns, mosses and liverworts. At every opportunity, Watts would carefully gather, press and document these delicate plants, making detailed observations about their growth habits and habitat. Over a lifetime of dedicated collecting within Australia, Watts discovered more than 200 species of ferns, mosses and liverworts. These specimens, collected as an enjoyable pastime, continue to support important research into cryptogams today. 

Collector - Watts

The Reverend William Walter Watts in the field with his plant press and vasculum, a container which keeps field samples viable by maintaining a cool, humid environment.


Lichen is not a single life-form, but a symbiosis - a partnership between a fungus and a green alga or cyanobacterium growing together.

There are more than 20,000 known species of lichen. Through history, humans have found many uses for lichen as dye, food, animal fodder and medicines. Today, lichen’s main use is as a vital ingredient in the perfume industry. However, medical research shows that some lichen species contain substances with antibiotic properties, while others could potentially treat viruses and tumours.


Artwork by Margaret Flockton.


Soil is a living thing; a single teaspoon of soil contains billions of tiny organisms. Soil’s delicate and complex structure is formed over thousands of years. Healthy soil acts as a spongy reservoir for water and nutrients, and plays a vital role in the earth’s carbon and nitrogen cycles.

The typical undisturbed soil profile of the Cumberland Plain is derived from shale and, through tens of thousands of years, has weathered to form distinct layers. The top 40 cm of the profile (the A horizon) is relatively light in texture and is slightly acidic (pH 6), allowing good plant growth. It is home to worms and other creatures. Unfortunately, this part of the profile is often washed away or removed during excavation for new buildings.

The subsoil (the B horizon), which is orange in colour, is not very good for plant growth as it has a higher clay content and pH, holds water and does not supply good aeration for the roots. However, during dry times, this layer helps supply deep-rooted plants with vital moisture.



Over 1000 vegetation types are recognised in New South Wales, and they include subtropical rainforests, arid salt-bush plains and treeless alpine herb-fields. Across these diverse landscapes live over 5810 species of plants, coexisting with animals and other organisms in complex ecosystems.

The rainforests of New South Wales are the most varied in Australia, ranging from the lush subtropical forests of the north east, to dry vine thickets in the semi-arid west. Within these rainforests, a huge variety of plants and animals can be found, more than in any other vegetation type in the state.

Wet sclerophyll forests are found along the eastern escarpment and in coastal regions of New South Wales. Within these forests, eucalypts can grow to 70 metres tall, with broad-leaved shrubby or ferny understoreys. Occasionally, wildfire is part of these forests’ cycle of renewal.

Some of the most scenic parts of New South Wales are covered with dry sclerophyll forests with shrubby understoreys. Many of the understorey plants, which include waratahs, grow very slowly. Some have associations with fungi or bacteria, allowing them to better absorb nutrients from the poor soils on which they grow.


Rainforests. Image: Jaime Plaza van Roon


Wet sclerophyll forests. Image: Jaime Plaza van Roon


Dry sclerophyll forests



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