Machaerina articulata
Jointed twigrush (Machaerina articulata, formerly Baumea articulata) are exceptionally useful rushes for macrophyte zones in constructed wetlands. These tall rushes (up to 2.5m tall) tolerate fluctuating water levels and will grow strongly in areas where the water regime cycles from wet mud to water up to c. 1m deep, as well as more static conditions. Like other rushes, Machaerina articulata reedbeds stabilise wetland banks, however, they are more ‘aquatic’ than the other fifteen or more species of Machaerina (Baumea) in Australia and are therefore useful at slowing down water to increase treatment time. Being able to grow in dense stands in deep water and deep mud makes them especially useful for stormwater treatment in constructed wetlands that receive substantial volumes of sediment (e.g downstream of construction areas). Machaerina articulata establish readily from cuttings and will quickly form dense macrophyte beds in new constructed wetlands, reducing the period before full treatment performance is achieved and ensuring the wetland performs well for many decades.
Large rhizomes enable these plants to store energy during dry conditions and retain a fresh green appearance all through the year and in dry seasons. Colonial growth is rapid and the dense, upright reedbeds created by these plants are favourite habitats for many wetland fauna, including nesting waterbirds, frogs, insects (aquatic and terrestrial), spiders, small native fish and woodland birds and reptiles using the wetlands for drinking water. Dead culms (stems) and leaves form a thatch above the water level that is used by birds and other animals for nesting materials and for passage across deeper water. Their flowerheads (panicles), which are present from summer to early autumn, are large (c. 40cm long) and drooping and the resulting reddish-brown fruits are a significant food source for wetland birds and other seed eaters.
Habitat needs: still or slow-flowing fresh water. Wet mud to water c. 1m deep. Will colonise new areas within the wetlands once established.
Preferred position on a constructed wetland elevation gradient for the emergent plant, Machaerina articulata (Jointed twigrush), noting that it will grow into deeper water (c.1m) than other emergent plants.
Identification notes: stems cylindrical and rigid with internal horizontal divisions (septa) that can be felt by running fingers up the stem (culm). Septa often visible on older stems. Leaves are basal, as long as, or longer, than the stem and the leaf sheath is straw-coloured. Drooping inflorescence (flowers) c. 40cm long; flowers mostly summer to early autumn. Reddish-brown, egg-shaped and wrinkled nuts (c. 3-5mm) are typically consumed in autumn and winter by birds, which often remove the panicles as they feed leaving clean stems.
Conservation status: Common: SA, NSW, Vic, southern WA and QLD. Near threatened: Tas. Rare: ACT
Distribution of Machaerina articulata (Jointed twigrush) in Australia. Source: Atlas of Living Australia.