Plants of
South Australia
Caustis pentandra
Cyperaceae
Thick Twist-rush
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Adelaide
Arkaroola
Ceduna
Coober Pedy
Hawker
Innamincka
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Oodnadatta
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Botanical art

Kath Alcock paintings: 3.

Etymology

Caustic from the Greek 'kaustos' meaning burnt or scorched, referring to the dark leaf bases. Pentandra from Greek meaning five stamens.

Distribution and status

Found on Kangaroo Island, southern Mount Lofty Ranges and the South-east in South Australia growing in damp areas in heaths and open woodlands on sandy soils. Also found in all States except the Northern Territory. Native. Uncommon in South Australia. Rare in Tasmania. Common in the other States.
Herbarium regions: Eyre Peninsula, Southern Lofty, Kangaroo Island, South Eastern
NRM regions: Adelaide and Mount Lofty Ranges, Eyre Peninsula, Kangaroo Island, South East
AVH map: SA distribution map (external link)

Plant description

Wiry, erect perennial sedge with a short creeping root stock. Culms smooth, to 60 cm high and 8 mm diameter. Leaf sheaths very dark red-brown to blackish. Inflorescence with 5�12 distant clusters of branches, straight or somewhat spreading. Spikelets with 1 to 2-flowers; glumes 4�6, acute, long-mucronate (lower glumes) to short-mucronate (upper glumes), red-brown to dark grey-brown, puberulous; stamens 5; anthers 5.0�6.0 mm long; style 4�5-fid; persistent style-base 2.5�3.5 mm long, straw-coloured. Flowering between October and March. Fruits are slender brown drooping heads. Seed embryo type is capitate.

Seed collection and propagation

Collect seeds between January and May. Collect whole heads that are brown, containing dark hard seeds. Not all heads will contain seeds. Place the heads in a tray and leave to dry for one to two weeks. Then rub the heads with a rubber bung to dislodge the seeds. Use a sieve to separate any unwanted material. Store the seeds with a desiccant such as dried silica beads or dry rice, in an air tight container in a cool and dry place available.