If you venture down into the deeper protected gullies of the mountains, you might come across small areas of warm temperate rainforest. The tall trees form a dense canopy, blocking out much of the light to the forest floor. As a result, the ground is covered with ferns and other plants that can tolerate shade. You'll see plenty of mosses, lichens, liverworts, hornworts and fungi. And don't forget to look up into the branches of the trees - you may spot epiphytes, like species of ferns and orchids. Unlike parasites, these perching plants don't harm the host that they live on.
The most obvious trees of the Blue Mountains rainforests are coachwoods and sassafras. Also expect to see smaller trees - including the lilly pilly, with its dark green glossy leaves and pink berries; possumwood, with its small white spring flowers; cedar wattle; pepper bush; and grey myrtle.
Try looking for rainforests in the deep, sheltered gorges of Wentworth Falls - the Furber Steps-Scenic Railway track, or the Dardanelles Pass would be good places to start. Around Blackheath, you'll also find lush rainforests in the Grand Canyon.
Like open forests, woodlands tend to occur on the drier tops and upper slopes of the mountains. However, they need deeper soils and more protected sites. Here the canopy is even lighter than in an open forest and the trees are not as tall. Their crowns are often large and spreading.
Typical woodland trees include scribbly gums, mountain spotted gums and grass trees. Beneath them, you'll find a more open and grassy understorey, with a rich shrubland community. Look for woodlands in the same places as open forests - the cliff-top walks of Wentworth Falls, Katoomba or Blackheath would be a good place to start.
Dry eucalypt forests
Open eucalypt forests are so called because their canopy is relatively 'open', only blocking out between 30 and 70 per cent of the sky. These forests dominate the mountain region, growing in the dry, infertile soils of the sandstone plateaus, ridges and upper valley sides. If you take a walk along the cliff-tops of Wentworth Falls, Katoomba or Blackheath, you're almost certain to be surrounded by open forests, mixed with woodlands.
The trees are mainly eucalypts, including species like Sydney peppermint, black ash, red bloodwood, narrow-leafed stringy bark and hard-leaved scribbly gum. You'll also find turpentines, Sydney red gums and she-oaks.
The plants in the shrubby understorey of these forests generally have tough, leathery or spiny leaves. There are many flowering plants among them, including various species of banksia, grevillea, wattle and hakea. Look out for mountain devils, waratahs, flannel flowers, wax flowers, drumsticks, geebungs, wild irises and 'egg and bacon' pea flowers.
In closed forests, the canopy is dense, closing out most of the sky. You'll find these vegetation communities in cool, damp gullies and sheltered lower slopes facing east or south. Closed forest plants need deep, moist, fertile soil - and, because of this, they tend to be much taller than those of the open forests.
Trees of the closed forest include the majestic blue gum, Blue Mountain mahogany, turpentine, ribbon gum, Blaxland's stringybark and Blue Mountains ash. Among the understorey, you'll find smaller trees like cedar wattles, Sydney red gums, Christmas bushes, blueberry ashes, tea-trees and black wattles.
Twisted around the trees, you'll see climbers like the clematis, wonga wonga vine, dusky coral pea, native sarsparilla and wombat berry. The forest floor beneath will be covered with ferns (including the massive king fern), orchids, mosses and fungi. You might be lucky enough to spot bush flowers like the golden glory pea, white everlasting daisy and various boronia species.
So where can you find closed forests? Perhaps the most famous of them is the Blue Gum Forest, a magnificent stand of mountain blue gums purchased by bushwalkers in the 1930s. You'll need to walk into the Grose Valley to get there - try starting at Pierces Pass or Perrys Lookdown.
You know you're in heathland when you're surrounded by low, shrubby plants growing up to two metres tall. There might be also be the odd stunted tree. You'll probably be on the top of the mountain plateau, where the rock platform lies very close to the surface, and the soil will be thin.
There are two main types of heathland in the Blue Mountains, depending on the amount of water held in the soil. If the ground quickly loses its moisture, you'll find dry heathland. If it becomes waterlogged after a lot of seasonal rain, wet heathland will be the result.
The plants of the dry heathland grow in exposed sandstone areas with poor, shallow soil that dries out quickly. To minimise water loss, they have tough, leathery leaves or needle-like foliage. Many have also adapted to fire. They often have woody fruits, so that their seeds can survive a bushfire and then be released into the fertile, ashy ground. Some have lignotubers - fleshy stems at the base of the plant which shoot up with new life after fire has destroyed the crown.
You won't find many trees on the heath. Most forest trees can't survive in the exposed, shallow soils, so it's the low-growing mallee eucalypts that dominate here - species like Blue Mountains mallee ash. Other heathland trees include the dwarf she-oak, heath banksia and tea-trees.
Spring arrives in the Blue Mountains around September (in the Lower Mountains, east of Wentworth Falls) and October (in the Upper Mountains, west of Wentworth Falls). It scatters a brilliant range of wildflower colours across the heathland: pinks and mauves; whites and greys; yellows, creams and oranges. A variety of plants contribute to this vibrant collage - including boronias, pea flowers, heaths (Epacris species), guinea flowers, conesticks, wattles and flannel flowers.
In other words, few things are more beautiful than a springtime walk through the Blue Mountains dry heath. To see for yourself, try the Rocket Point Lookout Track, Cliff Top Track or Pulpit Rock Track.
Dry heathland tends to occur over sandstone, but you'll find wet heathland on shale rock platforms where the drainage is poor and the thin clay soil holds water. Here, only plants that can tolerate waterlogged conditions can survive - so the vegetation is very different to that of the dry heath.
In the wet heathland, you'll find shrubs like banksias, Epacris obtusifolia (a slender upright plant with clusters of waxy white tube-like flowers), Darwinia fascicularis and Sphaerolobium vimineum with its small yellow and orange pea flowers.
You'll see patches of wet heathland on the Overcliff-Undercliff Track.
Swamps occur in poorly drained areas that are constantly waterlogged. This can happen when there is an impermeable layer of bedrock underneath soils of clay and peat. Moisture builds up, unable to drain away or soak into the rock. There are two types of swamp in the Blue Mountains: the unusual hanging swamps and the valley swamps.
You'll see hanging swamps on hillsides and along cliff edges. They form in depressions, where water and organic matter have built up over time. If the mound of organic matter becomes higher than the depression it's sitting in, it can spill over into the valley below. The swamp will then gradually build up again.
Hanging swamps are made up of a great variety of sedges, rushes, grasses and shrubs. Plant species include the button grass, dagger hakea, pink swamp heath, coral fern and species of tea-tree. In summer, you'll sometimes see the beautiful red and gold flowers of Christmas bells just above the swamp.
You'll see hanging swamps on the Prince Henry Cliff Walk, Fairfax Heritage Track and the Pulpit Rock Track.
Valley swamps Over time, rivers can dump a great depth of silt and debris into the narrow valleys they flow through. In such confined gorges, you might find swamps surrounded by groves of grey-green sword grass. Crimson bottlebrush trees, acacias and melaleucas are also common around these plant communities.
Try looking for them in the Lower Mountains (east of Wentworth Falls), especially around Shaws Creek and Blue Gum Swamp Creek (just north of Wimmalee and Hawkesbury Heights).