The Australian Open Forest and Grassland Collection consists of native open forest, sandstone and grassland plant species.
This site was selected due to its slightly sloping nature with a northerly aspect which is representative of the topography these plants are accustomed to in their natural environment. Species displayed highlight a geographical collection of flora from a variety of vegetation types that are typically found in the Illawarra and Sydney. The wet and dry sclerophyll forest sections (sclerophyll meaning’ hard leaves’) highlight typical Illawarra open forest areas whilst the sandstone area displays heath and hanging swamp plants from both the Illawarra and Shoalhaven areas.
Initial planting began in 1977. In 1980 work commenced on the wet sclerophyll section with the planting of a number of eucalypt and turpentine trees which form the canopy. Within two years both the wet and dry sections were complete. In 2011, the Sydney sandstone section was incorporated into the collection. Forty years on from planting our older trees are now coming to the age when hollows are beginning to form in the trunks. These small hollows are already supporting a wide range of wildlife from nesting birds to sugar gliders and are vital for their survival. In time these hollows will increase in size and number to accommodate larger species like powerful owls. This highlights the importance of old growth forests as young forests have no hollows as homes to support diverse wildlife.
These plant communities demonstrate the changes in vegetation that occur gradually across the landscape as they progress from low nutrient shallow sandstone soils through to deeper, more fertile shale and claystone. In the natural environment, topography plays a major role in plant diversity due toits impact on winds, fire behaviour, rainfall patterns and the amount of solar radiation received.
Plants within these communities have adapted to their surroundings. For example, eucalypt leaves hang vertically which allows them to withstand severe wilting without lasting damage and reduces their exposure to the sun. This also lets light filter to the understorey plants below allowing these plants to thrive.
Plants grow slowly in nutrient-deficient conditions and some species have developed symbiotic relationships with nutrient-fixing bacteria and fungi to enhance nutrient availability. These plants exhibit other mechanisms to survive in soils with low fertility including re-using nutrients and an ability to retain and store phosphorus in their tissues. Nutrient cycles within the forests have evolved to recycle phosphates which are generally at very low levels in Australian soils.
The best time to view this collection is in spring to early summer.