Cyperus isabellinus K.L.Wilson APNI* Description: Slender annual or short-lived perennial, tufted. Culms obscurely trigonous to subterete, rather soft (therefore compressed when pressed and dried), smooth, 20–50 cm high, 1–2.5 mm diam.
Leaves usually septate-nodulose, mostly 2/3 as long as to equalling culms, to 3.8 mm wide.
Inflorescence simple or small-compound, with 6–12 branches to 12 cm long; clusters loose, subdigitate, hemispherical to globose, 10–50 mm diam.; involucral bracts leaf-like, 2–4 exceeding inflorescence. Spikelets flattened, 6–15 per cluster, 6–22(-38) mm long, 2.0–2.5 mm wide in side view, 8–18(-38)-flowered; rachilla narrowly to broadly winged; glume spacing 1.5–1.8 mm; spikelet falling as unit, or rachilla persistent. Glumes acute with straight mucro to 0.2–0.5 mm long, with sides 2- or 3-nerved, 2.7–3.4 mm long, straw-coloured to golden brown with very occasional red-brown blotches. Stamens 3. Style 3-fid.
Nut trigonous, narrow-ellipsoid to narrow-obovoid, nearly as long as glume, 1.8–2.5 mm long, 0.6–0.8 mm diam., pale yellow-brown; falling with glume.
Flowering: summer.
Distribution and occurrence: From near Charters Towers in Queensland south to Narrabri district. There are no records between the Qld border and Narrabri, but that presumably reflects lack of collecting at the appropriate time in the appropriate habitat. Grows in ephemerally wet situations on clay soils: in gilgais ('melon-holes') in brigalow (Acacia harpophylla) woodland or around depressions or along drains in belah (Casuarina cristata) woodland.
NSW subdivisions: NWP
Other Australian states: Qld
Text by K. L. Wilson (June 2012)
Taxon concept: KL Wilson, Telopea 4: 475-478 (1991).
APNI* Provides a link to the Australian Plant Name Index (hosted by the Australian National Botanic Gardens) for comprehensive bibliographic data
***The AVH map option provides a detailed interactive Australia wide distribution map drawn from collections held by all major Australian herbaria participating in the Australian Virtual Herbarium project.
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