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Gymnoschoenus sphaerocephalus FAMILY: Cyperaceae BOTANICAL NAME: Gymnoschoenus sphaerocephalus COMMON NAME: buttongrass CONSERVATION SIGNIFICANCE: None recorded Micah Visiou Description Buttongrass is a perennial sedge that forms large, densely-tufted, coarse tussocks from which arise long stalks (culms) bearing spherical flower-heads, which form the characteristic “buttons”. The greyish, yellow-brown leaf sheaths are up to 20 cm long, more or less shiny, finely-grooved and open, with long, brown hairs on the margin of the sheath apex and on the apex of the small papery structure (ligule) located at the leaf sheath–leaf blade junction. The leaf blade is smooth, hard, long (up to 60 cm) and narrow (1–2.5 mm wide). In cross-section, the leaf blade is flat on one side and rounded and curved outward (convex) on the other side, and is sometimes spirally twisted. The flower-head stalks (culms) are often 1 m or more in length, 1–2.5 mm in diameter, cylindrical or slightly flattened, finely-grooved but smooth, hairless and rigid with no nodes, bearing a globe-shaped flower-head at the top. The flower-head is dense, usually 1.5–2 cm in diameter, and cupped underneath by a whorl of leaf-like structures (involucral bracts) that are more or less circular and enfold the flower-head when in bud. These bracts have either sharp or leaf-like tips, are flat, up to 5 mm long and hairy at the base. There are also smaller bracts within the flower head, which are notched at the tip and pointy, with papery margins that rapidly become torn. The flower-head is composed of smaller units (spikelets) that are numerous, flattened and 5-6 mm long. Each spikelet has 6–7 yellow-brown, glistening leaf-like structures (glumes). The lower glumes are empty, papery and dark brown. The upper glumes are longer and more or less hardened, and enfold the flower units (florets). Each spikelet holds two florets. The upper floret is bisexual and the lower one is male. The male floret’s stamens have flattened filaments and 4 mm long anthers. The bisexual floret has a 5 mm long style and short stiff bristles attached below the ovary (hypogynous), which are either 2.5 mm or 4 mm long, or absent. The fruit (nut) is 4 mm long (including the reverse pyramid-shaped stalk). The fruit is reverse egg-shaped, with a persistent style base, the outermost layer of which is loose, thin and easily removed. When the fruit falls, it remains enfolded in the upper glumes. Flora of Tasmania Gymnoschoenus sphaerocephalus Confusing species None in Tasmania. Distribution and Habitat Distribution of Gymnoschoenus sphaerocephalus in Tasmania according 2004 data Buttongrass moorland distribution in Tasmania . TASVEG 2004. In Australia, buttongrass occurs in South Australia, Victoria, New South Wales and Queensland. In Tasmania, it occurs in the northwest, northeast, east coast, southwest and central highlands in areas of high rainfall on poor soils. On slopes where the drainage is better, buttongrass occurs in sedgeland heaths and other open communities. It develops into a hummock in low closed scrub and sedge communities. It is most common on peat overlying quartzite gravels, where it forms extensive areas of moorland from near sea level to an altitude of 900 m, where it is often the signature species. Buttongrass moorlands are widespread in northwestern, western and southwestern Tasmania. These moorlands dominate the landscape in the wetter southwest and western areas but occur only as small isolated pockets in the drier north and east. The eastern buttongrass moors occur mostly on poorly-drained flats or depressions with waterlogged soils or seasonally wet mineral soils, mainly loams and sandy loams. Ecology Buttongrass can thrive on very poor sites with low levels of nutrients and impeded drainage. Buttongrass employs a number of strategies to overcome the limitations of such sites. In response to low nutrient conditions, this species has evolved scleromorphic characteristics such as tough, long-lived leaves (culms) with high contents of oil, lignin and silica, which allow the plants to survive in the anaerobic, acid soils where the nutrient availability is extremely low. In the cool, wet, acidic conditions that prevail much of the year in the sites preferred by buttongrass, decomposition is slow so recycling of nutrients back into the soil is also slow and thus much of the nutrients are bound up in plant matter. As the long-lived leaves age, nutrients are probably withdrawn from the leaves and taken up by new rhizomes to Flora of Tasmania Gymnoschoenus sphaerocephalus maintain the nutrient supply to the tussock. After death, the leaves do not decay but remain attached to plants long afterwards. Over time a large amount of dead plant material accumulates, which tends to dry quickly after rain. These features make the plants very flammable and pyrogenic. Another feature is the white, fleshy (and edible) rhizomes, with the capacity for considerable carbohydrate storage, which enables the plants to recover after an adverse event such as fire or drought. These fleshy rhizomes form a dense bundle close to the surface, penetrating 5–10 cm below the peat. The structure of the rhizome elevates the tussock above the water table for at least some of the year, maximising the available oxygen and enabling the plants to cope with impeded drainage and lack of oxygen in the soil. At some sites, the rhizomes can form large pedestals (up to 50 cm high) and the top of the plants may reach 2 m in height. In some cases, rhizomes can penetrate the peat to depths of 15–20 cm and are often seen growing along the tunnels of burrowing crayfish (Parastacoides tasmanicus). In fact, buttongrass plants tend to be the preferred sites for the crayfish burrows. Evidence suggests that a symbiotic relationship may exist between the crayfish and buttongrass, where the crayfish improves aeration of the peat while the plant’s fleshy rhizomes provide a food source. Buttongrass is well adapted to fire and can recover vegetatively after fire. However, the tussocks can be killed by even a moderate fire if the conditions are dry or in areas where there is little peat cover, as the rhizomes require wet peat to protect them from heat damage. Regeneration after fire is quite rapid and buttongrass can produce shoots 10–20 cm long 3 months after a low intensity spring or autumn fire. Some plants can produce flower buttons 6 months after a mild autumn fire, which suggests they use the carbohydrates stored in the rhizomes prior to spring growth. The buttons generally appear 3–4 years after a mild spring fire, about the same time as new leaves appear. Flowering occurs during the following season, which for most tussocks is during late November and early December. In the absence of fire, the main flush of growth occurs early in spring, with flowering occurring from spring through to summer and seed produced from December through to March. Buttongrass is not an aggressive species and does not rapidly colonise areas. Rather, it seems to spread slowly in a stepwise manner from the parent plants. It is dispersed principally by seed rather than by vegetative spread. The seeds seem to require high light and moisture levels for germination. For example, waterlogged sites with patches of exposed soil or well-lit disturbed sites, such as those along roadsides and tracks, appear to be very favourable for germination. Seedlings are more likely to establish where there has been partial removal of peat and less likely to establish on bare quartzite, where the rhizomes have difficulty penetrating the rocky surface. Seedling densities observed are low, especially when compared with that observed in some shrub species. This observation is consistent with the discovery that the buttons produce few viable seeds. It is possible that buttongrass may be spread more widely via dispersal by birds, since its seed are a source of food for species such as ground parrots. If bird dispersal does occur it is apparently not a highly successful process, as itinerant seedlings or young plants of buttongrass are not encountered as widely as are those of Gahnia species Flora of Tasmania Gymnoschoenus sphaerocephalus (sawsedges) and Cenarrhenes nitida (native plum) for example, which are also dispersed by birds. Ant colonies may help disperse seed short distances, as they have been observed gathering buttongrass seed. Buttongrass is resistant to Phytophthora cinnamomi but acts as a host for this disease. Buttongrass is the signature species of buttongrass moorlands. Globally, this is a unique vegetation type. Potential for Cultivation The cultivation potential of this species is low. Buttongrass tends to produce few viable seed. The seed is very difficult to germinate, with the best results achieved when a heat bed is used. The flower stalks (culms) are currently used in basket making. The flower-heads are also generating some interest for use in floriculture. Information Sources Curtis, W.M. & Morris, D.L. (1994) The Student’s Flora of Tasmania. Part 4B. St. David’s Park Publishing, Hobart. Gellie, N.J.H. (1980) Fire Ecology of Buttongrass Moorlands. Bulletin 6. Forestry Commission, Tasmania. Jarman, S.J., Kantvilas, G. & Brown, M.J. (1988) Buttongrass Moorland in Tasmania. Research Report No. 2. Tasmanian Forest Research Council Inc. Marsden-Smedley, J. (1993) Fuel Characteristics and Fire Behaviour in Tasmanian Buttongrass Moorlands. A fire and research study conducted by the Protection Branch, Parks and Wildlife Service, Department of Environment and Land Management, Hobart, Tasmania. Marsden-Smedley, J., Catchpole, W.R. & Pyrke, A. (1998) Unbounded Burning in Tasmanian Buttongrass Moorlands. Unpublished report prepared for the Tasmanian Fire Research Fund. Parks and Wildlife Service, Forestry Tasmania and Tasmania Fire Service. Understorey Network. Tasmanian Native Species Database. www.understoreynetwork.org.au Walsh, N.G. & Entwisle, T.J. (1994) Flora of Victoria. Vol. 2. Inkata Press, Melbourne. Flora of Tasmania