1. Adonis annua L. (summer adonis)

A. autumnalis L.

Pl. 511 i; Map 2338

Plants annual. Stems 15–40 cm long, erect. Leaves alternate and in a basal rosette (this often absent at flowering), the blades 2–4 times pinnately dissected, the segments 0.5–1.0 mm wide, narrowly linear. Inflorescences of solitary flowers at the branch tips. Flowers actinomorphic, perfect. Sepals 5(–8), 4–9 mm long, oblong-elliptic, plane, green, purple, or nearly colorless, not persistent at fruiting. Petals 5–10, 7–15 mm long, 3–4 mm wide, plane, dark red, usually with a dark basal blotch. Stamens prominent but scarcely showy, the anthers dark purple (fading to olive green with age). Staminodes absent. Pistils 25–40, each with 1 ovule. Style present. Fruits achenes, in cylindrical heads 12–18 mm long and 6–9 mm wide, the body of each fruit about 3 mm long, broadly top-shaped, the outer wall thick, wrinkled or faintly veined, the tip tapered abruptly to a straight lanceolate beak about 1 mm long. Receptacle becoming elongated at fruiting, glabrous. 2n=16. April–May.

Introduced, Jefferson County (native of Eurasia, escaped at scattered localities in the southeastern U. S. from Alabama to Texas and Missouri). Crop fields and open disturbed areas.

This species was once a well-known weed of grain fields all over the world, but it has largely disappeared from this habitat as farming techniques have changed. The few Missouri collections and reports were made in the 1930s and 1940s, thus it may no longer escape in the state. Steyermark (1963) reported this plant as Adonis aestivalis L. but our specimens are clearly A. annua. He also stated that the petals are yellow, rather than red. This may have been caused by the red petals sometimes fading to yellow in dried herbarium specimens.