Plant: perennial or annual herb or subshrub; to 1 m tall, minutely stellate-puberulent Leaves: broadly ovate to (in ours) narrowly oblong-lanceolate, dentate, 2-4 cm long, discolorous Flowers: solitary (or grouped) in the leaf axils, sometimes crowded apically; calyx 5-7 mm long; petals yellow (rarely white); styles 5 Fruit: FRUITS broadly conical, 4-5 mm diameter; mericarps 5, with apical spines ca. 1 mm long, these antrorsely pubescent; SEEDS solitary, glabrous Misc: Open arid slopes and sandy plains, sometimes in fields; 1050-1200 m (3500-4000 ft); flowering throughout the year REFERENCES: Fryxell, Paul A. 1994. Malvaceae. J. Ariz. - Nev. Acad. Sci. Volume 27(2), 222-236.
Annual herb 30- 60 cm tall Stem: erect, branched, and often with spine-like projections at leaf bases. Leaves: many, alternate, stalked, shallowly blunt-toothed, 2 - 4 cm long, egg-shaped to oblong-elliptic with pointed tips. Flowers: axillary, clustered, short-stalked (longer stalks jointed near middle), pale yellow, 0.8 - 1.5 cm wide, radially symmetric, with about 0.6 cm tall calyx, flaring petals, but no bractlets subtending sepals. Sepals: five, but fused at base for less than half their length, then separating into five somewhat egg-shaped lobes with pointed tips. The calyx as a whole is thinly covered with star-shaped hairs, and the fused basal portion is obviously angled. Petals: five, pale yellow, 0.4 - 0.6 cm long, widest toward somewhat oblique tips, but without teeth or notches along apex. Stamens: numerous, but filaments fused into an elongate tube with the anthers protruding near the top. Pistil: enclosed by the stamen tube, with five superior carpels (ovule-bearing structures), styles coming up through center of stamen tube, and ending with exserted, round-tipped stigmas. Fruit: five, one-seeded, about 6 mm long, somewhat oval, stiff-hairy, two-beaked segments (mericarps) enclosed by the persistent sepals. Each mericarp has two sections, the lower section (under 0.5 cm long) containing the seed, and a short-stiff-hairy, more membranous border section along the outer and upper edge of the seed-bearing portion, which ends in two, 2- 3 mm long, apical, sharp-pointed beaks.
Similar species: In our area, Sida spinosa is most similar to Anoda cristata, but that species has bluish axillary flowers on very long stalks, larger leaves (5 - 10 cm long), more fruit sections (mericarps eight to twelve), only one beak per mericarp, and in fruit the sepals become flattened and create a saucer upon which the mericarps sit. Also possibly similar is Malvastrum hispidum since it too has yellow axillary flowers on short stalks, but it always has three narrow bractlets directly below the sepals, the sepals are not fused (though very closely touching) but become winged in fruit, the petals are shorter (not over 4.5 mm), and the fruit segments are rounded and have no beaks.
Flowering: August to October
Habitat and ecology: Introduced from tropical America, mostly a weed of cornfields and other cultivated ground, especially in the most southern counties of the Chicago Region.
Branching annual 3-6 dm, commonly with a short spine-like process at the base of each lf; lvs petiolate, 2-4 cm, crenate, lance-ovate to oblong or elliptic, basally subtruncate to subcordate; fls fascicled in the axils; pedicels 2-12 mm, the longer ones jointed near or above the middle; cal thinly stellate; pet pale yellow, 4-6 mm, carpels 5, each tipped with 2 erect, hispidulous beaks; 2n=14, 28. Fields, roadsides, and waste places; pantropical, extending n. occasionally as far as Mass. and Mich. July-Oct.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Fryxell 1994, Wiggins 1964, Kearney and Peebles 1969
Duration: Perennial Nativity: Native Lifeform: Subshrub General: Herbs or subshrubs, rarely annuals to 1 m tall, minutely stellate-puberulent. Leaves: Broadly ovate to narrowly oblong-lanceolate, dentate, 2-4 cm long, discolorous. Flowers: Solitary (rarely grouped) in leaf axils, sometimes crowded apically, calyx 5-7 mm long, petals yellow (rarely white); 5 styles. Fruits: Broadly conical, 4-5 mm diameter, 5 mericarps, apical spines about 1 mm long, antrorsely pubescent. Ecology: Found on open arid slopes and sandy plains, sometimes in fields from 3,500-4,000 ft (1067-1219 m); flowers throughout the year. Notes: Diagnostic is its erect habit, 5 mericarps about 1 mm long, and stellate-puberulence. Ethnobotany: Unknown Etymology: Sida is the name Theophrastus gave to the lily, spinosa means spiny. Synonyms: Sida alba, Sida angustifolia, Sida spinosa var. angustifolia Editor: SBuckley, 2010