Seeds of South Australia
Caustis pentandra (Cyperaceae)
Thick Twist-rush
List of species for Caustis
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Seed collecting:
January to May
Herbarium regions:
Eyre Peninsula, Southern Lofty, Kangaroo Island, South Eastern
NRM regions:
Adelaide and Mount Lofty Ranges, Eyre Peninsula, Kangaroo Island, South East
IBRA regions
Bridgewater (NCP01)Naracoorte Coastal Plain
 Rare   (IUCN: RA d(ii))   [edge of range]
Glenelg Plain (NCP02) 
 Rare   (IUCN: RA d(ii))   [edge of range]
Lucindale (NCP03) 
 Least Concern   [likes sand]
Tintinara (NCP04) 
 Least Concern   [likes sand]
Kangaroo Island (KAN01)Kanmantoo
 Least Concern
Fleurieu (KAN02) 
 Critically Endangered   (IUCN: CR B2ab(i,ii,iii,iv,v))   (Probable Decline)   [localised to Mt Compass; outlier pop; deep sand sp; could be extinct]
Eyre Hills (EYB03)Eyre Yorke Block
 Vulnerable   (IUCN: VU D2)   [resilient species]
Lowan Mallee (MDD04)Murray Darling Depression
 Near Threatened   [deep sand spp]
RSCA map:
Regional Species Conservation Assessments per IBRA subregion. Please click the thumbnail map.
AVH map:
Australian distribution map (external link)
SA Census:
Census of South Australian plants (external link)     [genus Caustis]
Name derivation:
Caustic from the Greek 'kaustos' meaning burnt or scorched, referring to the dark leaf bases. Pentandra from Greek meaning five stamens.
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.
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.
Fruit type:
Slender brown drooping heads.
Embryo type:
Seed collecting:
Collect whole heads that are brown, containing dark hard seeds. Not all heads will contain seeds.
Seed cleaning:
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.