Beginning with only a few remnant species and the natural creek line, plans were made in the late 1970s to create an area to resemble the Illawarra rainforest. Initial plantings took place in 1978 although major regeneration works were not undertaken until 1981 when 600 species native to the Illawarra were planted.
The current rainforest collection consists of both native and exotic rainforest communities. Dense plantings of tree species form the canopy and complement the remnant stands of Turpentine and Melaleuca to form part of the closed canopy, allowing only filtered sunlight as seen in natural rainforest systems. Mixed plantings of shrubs, ferns, epiphytes and ground covers represent the natural composition of a rainforest community allowing visitors to view these species in conditions they would naturally occur.
The Rainforest collection showcases a number of rainforest communities from Australia and abroad. The Illawarra Rainforest, the south-eastern component of this collection, is home to approximately 80 different species of trees and 15 different fern species from the region’s dry, subtropical and cool temperate rainforests. Further north along the creek line species found in tropical North Queensland are represented. Small island beds have been created to display rainforest species found in New Caledonia, New Zealand, Lord Howe Island and South Africa. These geographical areas were selected due to their compatibility with the Illawarra climate.
Rainforests require high annual rainfall and are usually associated with high nutrient volcanic soils. These soils are well drained, deep and fertile. Generally rainforest plants are evergreen and have leaves with large surface areas to catch sunlight and shed water quickly. For this reason, most of the collection can be viewed all year round though the epiphytes flower in spring.
Rainforest species require shelter from westerly winds and thrive in a south easterly aspect where moisture loss from winds is minimised.
Rainforest seedlings are able to germinate in dense shade and will sit dormant until a gap in the canopy opens; this is usually the result of the death of older trees. Young seedlings then compete for the newly created space in a process called ‘gap phase dynamics’.
Remnant Illawarra rainforests account for only three percent of the state’s rainforest areas and contain about a third of all rainforest species in NSW. Many of these species are endangered or listed as vulnerable including Daphnandra johnsonii Illawarra Socketwood and Zieria granulata Illawarra Zieria. These are both endangered species endemic to the Illawarra region. Other species such as the Toona ciliata Australian Red Cedar were devastated by logging in the early 1800s, with many more species affected by clearing for agriculture.