Brockman National Park
The Pemberton Parks:
The Pemberton area is famous for the beauty of its majestic karri forest. Brockman, Beedelup and Warren National Parks are good places to explore the cool, soft understorey which is typical of the karri forest.
Brockman National Park:
The 49-hectare Brockman National Park, which takes its name from Brockmans Station, now known as Yeagarup Historic Homestead, provides a magnificent entry to the Pemberton area, on the road from Northcliffe and south of the Warren River. Here, the road winds its way through the tall, straight karri trees which line the main road. Below the karri trees is the typical understorey of smaller trees and large shrubs. The peppermint, karri sheoak and the yellow blossoms of the karri wattle mix with other large shrubs, such as the karri hazel.
In the Cool of the Karri:
Karri (Eucalyptus diversicolor) is one of the world's tallest hardwood species and may grow to almost 90 metres high. It is native only to the wetter areas of south-western Australia. Karri occurs in patches, often mixed with other forest trees to make up a mosaic of forest formations, interspersed with sedgelands and heathlands.
Most karri grows between Manjimup and Denmark, with outlying populations found as far west as Margaret River and Boranup, near Hamelin Bay, and as far east as the Porongurup Range and Mount Manypeaks. However, its development is best in the Manjimup-Pemberton-Walpole area. Near Pemberton, the Warren, Beedelup and Brockman national parks afford some of the State's best karri forest scenery.
The karri forest understorey is particularly soft and lush, occurring in areas of high rainfall, generally with 1100 millimetres or more each year. This understorey helps to give the karri forest its character, particularly on cool and misty mornings, when the sunshine tries to rise above the mist and the dew lies heavily on the foliage.
Relatively few species are actually restricted to the karri forest itself, although there are many restricted to the adjacent outcrops of granitic rocks (monadnocks) or to adjacent swampy sedgelands. Most karri forest species can also be found in neighbouring jarrah-marri forest and many appear in the nearby coastal heaths, where they often grow as wind-pruned shrubs. For example, deep in the karri forest the peppermint (Agonis flexuosa) and the bull banksia (Banksia grandis) are well developed trees, often ten metres high, but on exposed coastal headlands both may be reduced to small, stunted shrubs.
The overall impression of the understorey is of a soft, dense, dark green shrubbery. However, in spring it comes alive with the vivid deep bluish-purple flowers of the tree hovea (Hovea elliptica) and the native wisteria (Hardenbergia comptoniana), which contrast strongly with the cream flowers of old man's beard (Clematis pubescens) and the delicate, white to pale pink, star-shaped flowers of crowea (Crowea angustifolia), which are all mixed with a sprinkling of yellow blossoms of hibbertias and wattles.
Even the other trees and large shrubs in the understorey are dwarfed by the tall karris. The peppermint tree can be recognised by its soft pendulous foliage, clusters of tiny white flowers and the peppermint-like smell of its leaves when crushed. This odour is characteristic of many species of the family Myrtaceae. Another tree is the delicate karri sheoak (Allocasuarina decussata). It has a thick, corky bark with numerous vertical fissures, in complete contrast to the smooth bark of the karri trees. The leaves of karri sheoak are reduced to whorls of tiny scales around the joints of its needle-like branchlets. The plant has tiny separate male and female flowers, which are pollinated by the wind. Also typical of the tree layer is the bull banksia, with its very large, leathery, saw-toothed leaves and large candles which each carry hundreds of tiny yellow flowers. The river banksia (Banksia seminuda) and swamp banksia (Banksia littoralis) both have narrower, and more finely-toothed, strap-like leaves.
The shrub layer includes many large to medium-sized shrubs. The most common of these is the karri wattle (Acacia pentadenia). It has leaves which are divided into many small leaflets, fluffy yellow blossoms and a fairly strong odour which characterises karri forest. Other large shrubs include karri hazel (Trymalium floribundum), which has fairly large, softly hairy leaves and sprays of small, cream coloured flowers, and chorilaena (Chorilaena quercifolia), with its indented oak-like leaves. Its cream to green "flowers" actually hide a cluster of six tiny true flowers. Chorilaena is one of the species which may also grow in coastal heath as a wind-pruned shrub.
There is great variety in the small to medium-sized shrubs too. Hibbertia species, with their bright yellow buttercup-like flowers, include cutleaf hibbertia (Hibbertia cuneiformis) and karri hibbertia (Hibbertia serrata). Another characteristic plant is the brilliant deep bluish-purple pea flowers of the tree hovea. A shrub with a bizarre appearance is the erect, bamboo-like tassel flower (Leucopogon verticillatus), which has whorls of fairly rigid, bright green leaves up its stems and spikes of very tiny, pinkish-red flowers. You can also see the conspicuous white to pink flowers of crowea, and the softly hairy Lasiopetalum and Thomasia species, with their delicate creamy or purple flowers. Sometimes common are the delicate flower heads of the banjines, such as the bunjong (Pimelea spectabilis), with its large heads of small white to pale pink tinged flowers, some five centimetres across.
The narrow-leaved oxylobium (Oxylobium lineare), which has attractive sprays of 'egg and bacon' pea flowers, often fringes watercourses. So does the native willow (Callistachys lanceolata), distinguished by its sprays of yellowish-orange pea flowers. Another member of the pea family, water bush (Bossiaea aquifolium), is also common in the karri understorey. Its leaves have prominent spiny-toothed margins and are arranged in opposite pairs along the stem.
Because of the density of the vegetation, creepers which chase the light by climbing surrounding shrubs are common components of the understorey. The bright bluish-purple flowers of native wisteria, the pink to red flowers of coral vine (Kennedia coccinea) and the cream flowering clematis are frequently found together, making a beautiful display in spring.
Smaller shrubs and herbs are often more cryptic, but a search under the taller shrubs and in small clearings may reveal hidden delights. Aniseed boronia (Boronia crenulata) and karri boronia (Boronia gracilipes), with their tiny star-shaped pink to red flowers, contrast with the sprawling, blue-flowered karri dampiera (Dampiera hederacea) and the softly hairy foliage of tremandra (Tremandra stelligera), with its mauve flowers. Also typical are the bright yellow flowers of the prostrate hibbertia (Hibbertia grossulariifolia). Occasionally seen are delicate pink or white triggerplants, fanflowers, a range of beautiful orchids, smaller pea flowers and a myriad of small sedge-like species. Other components of this moist environment include the maiden-hair fern (Adiantum aethiopicum), mosses and liverworts on rotting fallen logs and, particularly in autumn, the occasional delicate toadstool.