Common name: Spinyhead Sida
Sida acuta Burm.f. APNI* 
Description: Subshrub or herbs to 1.5 m high, slender, erect or spreading, stems pubescent with simple and minute stellate hairs or subglabrous.
Leaves ovate, oblong, lanceolate or narrow-lanceolate, 2–9 cm long, 5–40 mm wide, apex acute or acuminate, base obtuse to rounded, sometimes partly entire towards base, margins serrate-crenate, surfaces glabrous or sparsely stellate pilose, rarely with simple hairs above; stipules linear to lanceolate, up to 10 mm long, 1.5 mm wide, sometimes with those of a pair unequal, one linear and the other lanceolate.
Flowers solitary or occasionally in crowded heads in the leaf axils; pedicels 4–12 mm long, pilose, articulate at middle. Calyx 6 mm long, mostly glabrous, margins often ciliate, lobes caudate-acuminate. Petals yellow, less often white or yellow-orange, 6–9 mm long, apex rounded, ciliate.
Fruit nearly globose, 3–5 mm diam.; mericarps 5–8, basally transversely ridged, reticulate on lateral wall, glabrous, rounded on back, apically 2- awned.
Flowering: Flowers mid to late summer.
Distribution and occurrence: Widespread weed of pastures and crops, seeds prolifically. One recent collection in Sydney. Native of C Amer.
NSW subdivisions: *CC
Other Australian states: *Qld *W.A. *N.T.
The bark is a good fiber source, and the roots are used medicinally.
Text by A. S. Mitchell & E. H. Norris
Taxon concept: Flora of NSW 1 Suppl. (1999)
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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