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 to burnt or scorched; referring to the dark leaf bases. Pentandra from Greek meaning five stamens.
Distribution:
Found on Kangaroo Island, the 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.
Status:
Native. Uncommon in South Australia. Rare in Tasmania. Common in the other states.
Plant description:
Wirey, 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:
Capitate.
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.