Drought proofing your backyard bush tucker patch requires establishing a well-mulched framework of hardy native grasses, sedges and rushes. These should be selected from those that are represented in our drought tolerant native vegetation communities. Within their inter-tussock spaces delicate herbaceous natives can be planted. Remember that these drought adapted herbs, with their lush green leaves and colourful spring flowers will die back to their underground rootstocks by the onset of our dry summer and autumn. However they reappear in all their splendour by early spring. Hence this is a garden style that relies solely on rainfall and will happily survive the droughty periods without supplementary watering.
Of the drought tolerant framework plants, the Saw-sedges (Gahnia sp.) are worthwhile trying. They are typically hardier than most other members of this Sedge Family known as Cyperaceae. The Papyrus Sedge, biblically referred to for its use in Egyptian papermaking and the bulbous rooted Water Chestnut, used, as tasty crunchy additive in Chinese style cooking are well known members of the Cyperaceae family. This article focuses on the Saw sedges, which are not only drought tolerant, but also possess a set of fascinating attributes.
The best-known member of the Saw Sedge genus is the large Cutting Grass Gahnia grandis. Although generally considered too big for our bush tucker patch, it along with the Red Fruit Saw Sedge Gahnia sieberiana can take pride of place as feature plants. Fringed by 2 metre strap-like leaves, their long plume-like flowering heads and bright red fruits, present wonderful landscaping potential. Typical of the Saw sedges, they have thin weeping leaves with their distinctive sharp saw-like leaf edges, formed from tiny granules of silica incorporated into the leaf surface. Many an unsuspecting bush walker's limbs have been deeply gashed as a consequence of these sharp leaves brushing across their unprotected skin. Fingers often suffer deep wounds when trekkers grab its foliage when pushing through the obstacle course formed by their large tussocks.
Interestingly, Cutting grass relies on birds such as the Currawong for germinating its seed, more correctly referred to as small nuts. The Currawong eats and regurgitates the red flesh covered seed, with the aid of a gullet full of water. This helps purge out a reddish bolus of partially digested fruits. The Currawong's stomach acid etches these seeds weakening their tough seed coats to allow ease of germination. This is a intriguing example of how co-evolution between native plants and wildlife ensures mutual benefits for both.
Common in the drier woodlands is the Thatch Saw-sedge (Gahnia radula) with its characteristic thin leaves that droop markedly at their tips. This rapidly browning landscape of summer is punctated with drifts of dark brown flowers, dashed with the cream colour of their thread-like anthers. These supply pollen to the delicate Chaostola Skipper butterflies whose larva (caterpillars) occupies a cylindrical shelter constructed from 2 or 3 leaves drawn together and bound with silk. The mottled brown and yellow butterflies remain in close flying distance to the flowers during the October to December period.
Both the Flame Skipper and Donnysa Skipper butterflies also rely on either the Thatched Saw Sedge or Large Cutting Grass for their survival. The male Donnysa Skipper is very territorial, engaging other males in spiralling flights as it endeavours to defend its patch and attract females. Once mated, tiny yellowish green eggs are laid under the leaves, hatching into caterpillars with distinctive dark streaks along their green bodies. This camouflage only partially protects them from the native birds, which successful scavenge large numbers to feed their young nestlings.
By late summer, the Thatch Saw Sedge's flower heads ripen to form hundreds of small nuts. Once harvested, these nuts can be pounded and ground into flour for making flat breads. The young leaf bases can provide a tasty pea-like snack when harvested from plants grown with sufficient soil moisture. The waist high leaves can be woven into traditional items such as baskets and dillies. Traditionally they are split, left to dry for a few days and stored for later use. To render them pliable for weaving they require dampening for a day.
Large expanses of the Chaffy Saw Sedges (Gahnia filum) in association with Coastal Tussock and Spear grasses, frequently occupy the margins of brackish estuarine marshes and saline water bodies. Common in the Lauderdale and Pittwater inter-tidal wetland flats these sedges form part of the crucial habitat for many of our migratory birds. Their roots also act as hosts for the microbes that filter the detritus from the nutrient laden tides thus performing a fundamental role in the food web for these wetland communities.
Along with the Coast Saw Sedge (Gahnia trifida) they host the erratic flying Chrysotricha Skipper butterfly. Their larva have the unusual habit of twisting adjacent leaves together in a spiral fashion to form their characteristic shelter.
Gahnia rodwayi, is the smallest and most compact of all the Saw sedges. It is ideally suited to planting in dry grassland patches. Since it is listed as a rare plant, growing this little beauty helps increase its rapidly diminishing populations. However, like Gahnia radula even though the seed is easily collected, its propagation is more of an enigma.
Finally, as many bush tucker gardeners enjoy propagating their own plants, the challenge of successfully culturing these Saw Sedges awaits the enthusiast and all the green-fingered readers.
Phil Watson