Leaves shallowly lobed or more often unlobed, margins entire to toothed; petioles usually short.
Flowers axillary, solitary or in terminal heads or spikes; peduncles often jointed. Epicalyx absent. Calyx 5-lobed, often 10-ribbed at base in fruit. Petals yellow to orange. Staminal tube slender. Ovary 5–10-locular, each loculus 1-ovulate; styles as many as loculi; stigmas terminal, capitate.
This group requires much taxonomic attention; recent studies indicate that only 4 of the N.S.W. species (numbered 3–6) should be included in Sida s. str. with the remaining species assignable to other genera. Several undescribed taxa that are poorly known have not been included in this treatment.
| | Key to the species | |
| 1 | Mericarps distinctly awned and calyx distinctly ribbed at the base, or mericarps covered with stout spines and calyx prominently veined, or mericarps winged | 2 |
| Mericarps not distinctly awned, not covered with stout spines or winged, but sometimes deeply wrinkled, grooved or with short points; calyx not prominently ribbed or veined | 7 |
| 2 | Mericarps winged or covered with stout spines | 3 |
| Mericarps distinctly awned and calyx with 10 definite ribs at base when in fruit
Back to 1 | 4 |
| 3 | Mericarps covered with long stout spines | Sida platycalyx |
| Mericarps with prominent ribs or wings
Back to 2 | Sida goniocarpa |
| 4 | Flowers on peduncles 10–30 mm long; mostly solitary | 5 |
| Flowers on peduncles <10 mm long; in dense clusters or solitary
Back to 2 | 6 |
| 5 | Plant with a persistent short grey tomentum; flowering calyx 6–10 mm long; mericarps with apical points 3–5 mm long, armed with retrorse hairs | Sida rohlenae |
| Plant glabrescent; flowering calyx 5–6 mm long; mericarps with apical points to 1 mm long
Back to 4 | Sida rhombifolia |
| 6 | Leaves with a soft or short tomentum or glabrescent; fruit with barbs on the spines of the mericarps | 23 |
| Leaves glabrous or with hairs on margins; fruit without barbs on the spines of the mericarps
Back to 4 | Sida acuta |
| 7 | Flowers 2–15, clustered in axils, sometimes forming dense spikes | 8 |
| Flowers solitary or in pairs in axils or in cymes
Back to 1 | 11 |
| 8 | Peduncles 5–10 mm long; mericarps 7–10 per fruit | Sida pleiantha |
| Peduncles 0.5–3.5 mm long; mericarps 4–6 per fruit
Back to 7 | 9 |
| 9 | Shrub to 2 m high; flowers more or less sessile, few to several in clusters on axils, often forming a terminal spike | Sida subspicata |
| Subshrub or herb less than 50 cm high; flowers on peduncles 1–3.5 mm long, 1–4 per axil
Back to 8 | 10 |
| 10 | Lamina ovate to obovate; stipules filiform; calyx lobes acuminate; mericarps 5 | Sida sp. A sensu Harden (1990) |
| Lamina narrow-ovate to oblong; stipules narrow-triangular; calyx lobes truncate; mericarps 6 or 7
Back to 9 | Sida sp. B sensu Harden (1990) |
| 11 | Leaf laminas either reniform with scales or ovate to triangular, less than 10 mm long, and plant often spiny | 12 |
| Leaf laminas not as above or if so then plant not spiny
Back to 7 | 13 |
| 12 | Perennial herb covered with minute scales; leaves reniform, more than 10 mm long | Sida leprosa |
| Small spindly subshrub with stellate hairs; branches sometimes ending in spines; leaves ovate to obovate, less than 10 mm long or absent
Back to 11 | Sida intricata |
| 13 | Fruit 7–10 mm wide; hoary, more or less flat on top; mericarps 9–12 | Sida cunninghamii |
| Fruit less than 7 mm wide; not hoary and flat on top; mericarps less than 8 (6–10 in Sida corrugata)
Back to 11 | 14 |
| 14 | Calyx 6–12 mm long in fruit; plant with a dense tomentum often yellow- or brown-tinted | 15 |
| Calyx less than 5 mm long in fruit; plant mostly grey- to green- tomentose or glabrescent
Back to 13 | 16 |
| 15 | Calyx lobes ovate-triangular, finely stellate-pubescent often with dark hairs, to 12 mm long in fruit; plant with a yellowish grey tomentum | Sida petrophila |
| Calyx lobes narrow-triangular, obscured by thick brown stellate hair; to 10 mm long in fruit; plant with yellowish brown tomentum
Back to 14 | Sida phaeotricha |
| 16 | Flowers cymose, 3–7 (sometimes appearing solitary); fruit hardly wrinkled on sides | Sida fibulifera |
| Flowers 1 or 2 in axils; fruit wrinkled on sides
Back to 14 | 17 |
| 17 | Flowers on peduncles 5 mm or more in length | 18 |
| Flowers on peduncles less than 5 mm long
Back to 16 | 22 |
| 18 | Fruit glabrous; the central apical region prominently raised | 19 |
| Fruit persistently pubescent (occasionally more or less glabrous in Sida trichopoda); the central apical region flat to rounded, hardly raised
Back to 17 | 21 |
| 19 | Mericarps 5; leaf laminas narrow-ovate to narrow-oblong, 10–50 mm long, 2–11 mm wide | Sida ammophila |
| Mericarps 5–8; leaf laminas mostly ovate, ovate-cordate to lanceolate, 5–30 mm long, 5–22 mm wide
Back to 18 | 20 |
| 20 | Prostrate to erect subshrub less than 30 cm high; leaves with persistent dense velvety tomentum, grey-blue turning green above, grey-green below; flowers on peduncles to 15 mm long | Sida sp. C sensu Harden (1990) |
| Erect or procumbent subshrub to 60 cm high; leaves with a coarse to dense tomentum, often brownish and sometimes velvety; flowers on peduncles to 40 mm long
Back to 19 | Sida filiformis |
| 21 | Flowers on peduncles to 60 mm long; corolla 5–15 mm long; leaves linear to ovate-oblong, 2–15 mm wide | Sida trichopoda |
| Flowers on peduncles to 15 mm long; corolla 4–7 mm long; leaves circular to ovate
Back to 18 | Sida corrugata |
| 22 | Leaves ovate to obovate; stipules filiform; calyx lobes acuminate; mericarps 5 | Sida sp. A sensu Harden (1990) |
| Leaves narrow-ovate to oblong; stipules narrow, triangular; calyx lobes truncate; mericarps 6 or 7
Back to 17 | Sida sp. B sensu Harden (1990) |
| 23 | Plant with a persistent, soft yellowish green tomentum; leaves 10–40 mm wide; mericarps 8–10 per fruit | Sida cordifolia |
| Plant with a short grey-green tomentum, often glabrescent; leaves 4–15 mm wide; mericarps 3–5 per fruit
Back to 6 | Sida spinosa |
