Trees and Plants

There are some 8000 plant species in the South West region (or a third of all Australian plant species), 4000 of which are restricted to this area. By contrast, there are only 1500 plant species in the entire UK. An amazing 15% of species remain unnamed, and some have never been seen in their adult form. In 2017, 10 species that were previously thought extinct sprouted in their tens of thousands after fire cleared the leaf canopy, laid down a bed of nutrient ash, and exposed the seeds to solar warmth. This included the phoenix pennywort, which was found in the burnt out karri forest near Northcliffe after most probably lying dormant for decades. The uniqueness of the area has promoted some scientists to try to get UNESCO world heritage listing for its natural area, parks and reserves. Unfortunately, few Western Australians or Australians seem aware of this amazing biodiversity on their door step.

When the first white settlers arrived, the whole of the South West was full of seemingly endless timber. And because it had never been harvested it was of huge size - what we would call a King Jarrah tree were every where. Intially the closest timber to Perth was harvested first, but then as these forests were depleted, rail lines had to be built to reach the further out timber. Eventually it grew into a net work of timber lines through out the South West. As the timber was depleted, the rail was removed and the rail trails used as roads or tracks.

Jarrah

Eucalyptus marginata is one of the most common species of Eucalyptus tree in the southwest of WA. Djara is the the Aboriginal name for the tree and the wood. Because of the similar appearance of worked jarrah timber to Honduras mahogany, jarrah was once called Swan River mahogany after the river that runs through Perth.

The jarrah is a eucalyptus that can grow to about 40-50 meters high, with a trunk diameter of three meters, although it is rare to see them that size now. The trunk of the jarrah is long, straight, and has no branches on it. It has rough grayish brown bark with vertical grooves, which sheds in long strips. It is only known in the SW coastal region of WA. It has adapted to the wet winters and dry summers, the nutrient poor soils and fire outbreaks of the Darling Scarp and surrounding country. Its adaptations are so perfect it has become the only tall forest in the world to exist in a truly Mediterranean climate.
Jarrah's long, straight trunks of deep reddish-brown coloured and beautifully grained timber make it ideal for cabinet making, flooring, panelling and outdoor furniture. When fresh, jarrah is quite workable but when seasoned it becomes so hard that conventional wood-working tools become useless. It is very durable, termite and water resistant, so it was an ideal choice for structural material on bridges, wharves, railway sleepers, ship building and telegraph poles. A large amount was exported to the UK, where it was cut into blocks and covered with asphalt for roads. Some ended up on German and Indian roads as well.

The nominal cutting cycle for jarrah forest has typically been 30 to 50 years between cuts (in the higher rainfall areas and where a selection cutting system has been used). Two areas near Jarrahdale are considered to have been harvested for logs five times. In less productive forest (such as in the eastern low rainfall sector) the cutting cycle has been longer and many areas have been harvested only once or twice since 1829. Most multiple use karri forest is intended to be managed on a rotation length of at least 100 years. A paper by Abbott and Christensen (1994) shows that the jarrah and karri forests are in ecologically good condition after up to 120 years of timber harvesting.

The northern jarrah forest near Perth are very valuable for domestic water supplies (the dams near Perth are in the forest), bauxite resources and tourism/recreation as well as the conservation of biodiversity.

The WA timber industry relied predominantly upon the Jarrah forests of the Darling Range and the Karri forests of the Southwest Australia region. The 1880s and the development of government railways assisted the industry.

In 2012, WA's northern jarrah forest was added to a list of Australia's ten most endangered landscapes. The list was compiled by a network of 26 leading ecologists from around Australia as part of the Innovative Research Universities and is the result of many factors including climate change.

If you are riding under flowering jarrah (or marri), you maybe riding at the wrong time of year - these two trees flower in January and February, the hottest time of the year.

Marri

Is one of the most important trees in the forests of WA and is one of the most common of the eucalypts found in the south-west forests of WA. It produces large amounts of blossom and nectar. When mature, the trees develop large hollows that make highly sought after nesting sites for many species including the endangered black cockatoos, western ringtail possums and owls. Marri belongs to a group known as bloodwoods because the trunks exude a dark red gum. The term 'marri' comes from the Nyoongar aboriginal word for blood. The tree itself was once commonly known as the red gum. Marri trees have the large "honky nut", whereas the jarrah has a much smaller thumb nail size nut.

Marri timber is the colour of honey. It is not used for construction purposes as it is not a strong timber being full of gum veins and having numerous faults. It is increasingly used for the production of fine furniture and is suitable for the manufacture of pulp. The Marri tree is not found outside of the south west corner of WA. Like Jarrah, Marri flowers in the peak of Summer - January and Feburary.

Yarri

Or blackbutt, is similar to the jarrah and is native to the southwest of WA. It is usually a tall tree, up to 45 m, and grows in the wetter jarrah and karri forest areas. It is not a harvestable timber as significant areas of its distribution are now covered by conservation reserves. "Yarri" is the Aboriginal name for the blackbutt tree.

Blackboys or Grasstrees

The best known name for the Xanthorrhoea is the blackboy, whereas in the South West, the Noongar name is balga. Blackboy refers to the vague similarity in appearance to an Aboriginal boy holding an upright spear. Some now consider this name to be offensive and prefer grasstree. Xanthorrhoea is important to the Aboriginal people. The leaf bases and roots were eaten, and the seeds ground into flour. The flowering spike can be made in to a spear for fishing, and the bottom of the flower spike can be used as a base for a 'fire drill' for making fire. The nectar from the flowers gives a sweet tasting drink. In the bush the flowers are used as a compass, as the flowers on the warmer, sunnier side of the spike (usually the north facing side) often open before the flowers on the cooler side facing away from the sun. The resin is used in spear-making and is an invaluable adhesive for Aboriginal people. Specimens can reach 600 years in age.

Banksia

Are trees or woody shrubs are easily recognised by their characteristic flower spikes and fruiting "cones" and heads. They are found in sandy or gravelly soil. When it comes to size, banksias range from prostrate woody shrubs to trees up to 30 metres tall. Banksia plants are naturally adapted to the presence of regular bush fires in the Australian landscape. They regenerate quickly from seed, as fire also stimulates the opening of seed-bearing follicles and the germination of seed in the ground. Heavy producers of nectar, banksias form a vital part of the food chain in the Australian bush, feeding all sorts of nectarivorous animals, including birds, bats, rats, possums, stingless bees and a host of invertebrates, as well as the Indigenouus people. Furthermore, they are of economic importance to Australia's nursery and cut flower industries. Perhaps the best known cultural reference to Banksia is the "big bad Banksia men" of May Gibbs' children's book Snugglepot and Cuddlepie. Gibb's "Banksia men" are modelled on the appearance of aged Banksia "cones", with follicles for eyes and other facial features. This book was written in 1918 while Gibbs was living in Perth. A replica of her child home home is in Harvey, where she spent her childhood.

Wildflowers

The wildflower collection in Western Australia is the largest on Earth, with more than 12,000 species in the state, and over 60% of which are found nowhere else. Thousands of different varieties carpet paddocks, bushland and nestle between rocks all the way from the Pilbara in the North to the southern coast of WA, an area of around 2.5 million square kilometres. In some areas, within a 10m square area you can see maybe up to 50 species. In the south, the Fitzgerald River National Park alone contains more species of flowers than the entire UK. The nearly six-month flowering season begins in the north of the State in June and July. By September it has moved south and reached Perth, before finishing in October and November throughout the forests and coastal heaths of the South West. Usually around 50 new species of wildflowers are identified in WA every year, often spotted eagle-eyed enthusiasts.

Dieback

You may see some small signs indicating die back free areas. Die back is is a soil-borne mould which causes root rot. The plant pathogen is one of the world's most invasive species and is present in over 70 countries from around the world. Of particular concern is the infection and dieback of large areas of forest and heathland which support threatened species in the south-west corner of WA. 40% of native flora of South West  plants are susceptible, including jarrah, grass trees, banksia, dryandra, hakea, zamia palms and grevillea. The loss of this flora in turn will impact on animals reliant on these plants for food and shelter, such as the southwestern pygmy possum and the honey possum. It is spread by soil transfer on tyres and foot wear, so in indicated areas it is essential you stay on the trail.

Where dieback infestation occurs, infested areas of Banksia forest typically have less than 30% of the cover of uninfested areas. Plant deaths in such large proportions have a profound influence on other plants and animals. In the south west, Banksia often occurs as an understorey to forests of Jarrah, another species highly vulnerable to dieback. Infestation kills both the Jarrah overstorey and the original Banksia understorey, and over time these may be replaced by a more open woodland consisting of an overstorey of the resistant Marri, and an understorey of the somewhat resistant parrot bush (a prickly leafed banksia).

The Kangaroo Paw is Western Australia's floral emblem, and are only found in the south west of WA. The eleven species of kangaroo paws are only pollinated by birds.

The Western Australian Christmas Tree is a semi parasitic (like mistletoe) tree that also photosynthesises. It obtains water and mineral nutrients from its hosts, usually any nearby plants, but small enough amounts as not to damage the host. It displays bright orange flowers around Christmas time.

This page is the property of Follow My Ride, a website detailing off road cycle tracks near Perth and in Western Australia.