JT002 – Friends of Warwick Bushland

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2. Big Jarrah Trees

This is a shady area with impressive jarrah trees, wildflowers in season and a low bench cut from a log. Understorey vegetation includes Native Wisteria, shrubs, sedges, and balgas, and is in excellent condition. This is a great spot for social meetings, meditation, or other restful activities.

Common Wildflowers

Winter – Native Wisteria (Hardenbergia comptoniana), Yellow Buttercups (Hibbertia hypericoides), Harsh Hakea (Hakea prostrata), Daviesia nudiflora

Spring – Morning Iris (Orthrosanthus laxiflorus), Milkmaids, Wedge Pea (Gompholobium tomentosum), Yellow Buttercups (Hibbertia hypericoides), Cowslip and Pansy Orchids

Late Spring & Early Summer – Mignonette Orchid (Microtis media), Cottonheads (Conostylis aculeata), Pineapple Bush (Dasypogon bromeliifolius), Jarrah, Candle Banksia

Summer – Elegant Pronaya (Billardiera fraseri)

Focus 3. Jarrah Trees

Jarrah (Eucalyptus marginata) is one of the most ecologically important and useful trees in the Southwest of Western Australia. In Warwick Conservation Reserve, jarrah trees form an intermediate tree canopy over banksia and under tuart trees. Flowering is abundant from late spring into summer, supporting honeyeaters and insects at a time when relatively few other plants are flowering.

Hollows of various sizes and depths in mature Jarrah and Tuart trees are extremely valuable as nesting sites for parrots and other birds in Warwick Conversation Reserve. These hollows take up to 150-200 years to develop, due to activities of termites, burrowing insects, wood rotting fungi and storm damage. The tree survives as long as the living outer rings of wood and protective bark remain intact. However, hollows can be lost to fires which are too intense and frequent. Bird species that use these tree hollows include the Twenty-eight, Red-capped, Elegant and Regent Parrots, the Western Long-billed Corella and potentially Carnaby’s, Baudin’s and Forest Red-tailed Black-cockatoos.

Eucalyptus marginata with beefly pollinator

Bat Box in a Jarrah Tree

Trees in Warwick Bushland

Focus 4. Balgas

Balgas are the common local type of grass tree and are formally known as Xanthorrhoea preissii. These are semi-arborescent (tree-like) monocots that dominate the understorey in many parts of Warwick Bushland. Their “trunk” is only made up of leaf bases held together by internal vascular tissue and resin. They are resilient to fire and usually resprout rapidly from the top. Their long, narrow, angular leaves are incredibly well protected from drought but are brittle and subject to senseless vandalism near trails. The rate of growth of balgas is very slow, as they only grow about 25 mm a year. Thus, a 5 m tall Balga would be 200 years old.

Balga flower spikes emerge from close to the top of the leaves and are up to 4 m long. They produce thousands of small white flowers that turn into hundreds of pointed seed capsules which contain black, short-winged seed. Seeds germinate readily but only a few become new grass trees and it takes decades for a trunk to form. Some balgas flower each year but many more flower after a fire. Old fallen flower spikes are common in western parts of the Jarrah Trail following the 2019 fire. Balga flowers are an abundant source of nectar and are pollinated by a diverse range of insects and birds.

Balgas are very important to the aboriginal people in many parts of Australia. Resin from the trunk was used for attaching blades to handles of tools and weapons, and as a medicine. Old flowering spikes were used as fishing spears. Flowering spikes were soaked in water to extract nectar as a sweet tasting drink. Flowering plants can also be used as a compass because flowers on the warmer, sunnier side of the spike (north facing) tend to open first.