The park's main plant communities are rainforests, eucalypt forests, heathlands and woodlands.
You'll find small pockets of warm temperate rainforest in the park's deeper protected gullies. This vegetation community features small stands of water gum and lilly-pilly, with an understorey of cabbage tree palms, coachwood and grey myrtle. Jerusalem Bay is a good area to look for rainforest - it's downhill of Cowan station on the Great North Walk.
You won't just find heathland plants on the drier tops and upper slopes of the plateau. Where it's more sheltered, and where the sandy soils are deeper, you'll find woodlands. These plant communities have a light canopy of trees growing above a rich understorey of shrubs. The trees include eucalypts - such as scribbly gums and red bloodwoods - together with several species of she-oak. Beneath them, in the understorey, look out for the spectacular waratah with its crimson flowers that grow up to 10 centimetres wide. You'll see woodlands on the Topham Track, Salvation Loop and Willunga Trig walks.
Dry eucalypt forests
In the gully slopes and moister sheltered valleys of the park's sandstone landscape, you'll come across open forests. This is where Sydney red gums (angophoras) - most famous of the Sydney sandstone trees - grow. Closely related to eucalypts, their smooth, pink-grey bark flakes off every spring to reveal a new orange layer underneath. In these vegetation communities, you'll also see red bloodwoods, Sydney peppermints and New South Wales Christmas bushes. Try looking around Bobbin Head.
On the lower slopes of western Pittwater (try The Basin Track), and parts of Cowan Water, you'll find taller, denser forests. Here, there are stands of spotted gum and grey ironbark, together with forest she-oaks and boronias. Look out for the burrawang, a low-growing primitive plant that looks like a cross between a fern and a palm.
Heathland is a low, shrubby community of plants. You'll find it where a large rock platform lies very close to the surface, so there's not much soil and either too little or too much water. Heathland plants generally don't grow above two metres, although you might see the occasional stunted tree.
There are two types of heathland in Ku-ring-gai Chase National Park:
Dry heathland You'll find this on the exposed top of the sandstone plateau - try looking along West Head Road. The sandy soil here contains few nutrients and dries out quickly, so plants have to be very tough. They often have woody fruits, enabling them to survive and then regenerate after bushfires. Many wildflowers grow in dry heathland, producing a blaze of colour in spring. Examples of dry heathand plants include banksias, bottlebrushes, grevilleas, tea-trees and boronias.
Wet heathlandThis type of vegetation grows over shale rock platforms which become waterlogged after rain. As you might expect, very different plants are found here. Much of the ground is covered with sphagnum moss; the upper storey is made up of plants like swamp banksia and sword grass. If you're in a wet heathland area, look out for insectivorous sundews, which trap small insects with their sticky mitts. Search for these around the edges of the park's hanging swamps, like those on the Salvation Loop.
Mangroves are small trees with thick, leathery leaves. They grow on mudflats, and have roots hanging from their branches, in the air. These roots, called pneumatophores, give the trees the air they need - otherwise they would 'suffocate' in the mud. Mangrove seeds germinate while still attached to the adult tree. Some grow in the mud around the parent, penetrating the mud at low tide. Others float away, finding another patch of mud to grow in.
You can find mangroves at the head of Cowan Water, and in bays like Towlers Bay.