1. Gossypium hirsutum L. (upland cotton)

Pl. 450 e, f; Map 2050

Plants annual (shrubs elsewhere). Stems 30–130 cm long, erect or ascending, usually branched, pubescent with spreading, simple or fasciculate hairs. Leaves mostly long-petiolate, the blades 3–10 cm long, broadly ovate to nearly circular in outline, 3- or 5-lobed, the base cordate, the lobes broadly triangular, tapered to pointed tips the margins entire, the surfaces pubescent with sparse to dense stellate hairs. Stipules tending to shrivel before flowering, 3–9 mm long, linear to elliptic-lanceolate. Flowers solitary or in small clusters in the leaf axils, the bractlets subtending the calyx 3, conspicuous and exceeding the calyx, 20–45 mm long, broadly ovate-cordate, overlapping, the margins incised with deep narrow lobes. Calyces 5–24 mm long, cup-shaped at fruiting, the sepals fused nearly to the tip, the lobes broadly triangular. Petals 25–55 mm long, the tips broadly rounded, the margin usually slightly irregular, white or more commonly pale yellow, sometimes pinkish- or purplish-tinged, often with minute dark glandular dots. Stamens numerous, the staminal column circular in cross-section, with a low crown of teeth at the tip, the anthers yellow. Pistils with 3–5 locules, the carpels closely fused. Style unbranched, with 3–5 linear longitudinal stigmatic areas toward the tip. Fruits capsules, broadly ovoid to nearly globose, dehiscing longitudinally from the tip, glabrous. Seeds 5–11 per locule, 7–10 mm long, narrowly obovoid, the body hidden by a dense covering of shorter white matted hairs and long fluffy white fibrous hairs. 2n=56. July–September.

Introduced, uncommon in southern Missouri north to the St. Louis and Kansas City areas (native of Mexico and Caribbean islands; widely cultivated and escaping sporadically). Roadsides, railroads, and open disturbed areas.

Gossypium hirsutum is the principal species of cotton grown in North America and has a history of cultivation dating far back into pre-Columbian times. In Missouri, cotton production occurs in the Mississippi Lowlands Division and to a lesser extent in adjacent Ozark counties. Lower-growing cultivars adapted to sandy soils seem to have replaced most of the taller bushier plants represented in the older specimens of escapes from cultivation.

Steyermark (1963) excluded this species from the state’s flora in spite of the existence of several older specimens, reasoning that it was unlikely to become established in Missouri for any great length of time. However, in the supplement to his flora, he readily accepted the inclusion of G. herbaceum L. (an Old World species), based on a single misdetermined collection of G. hirsutum made by Viktor Mühlenbach in the St. Louis railroad yards. Mühlenbach (1979) later reported additional specimens and corrected the report.