1. Salsola collina Pall. (slender Russian thistle)

Pl. 358 b, c; Map 1550

Stems 15–100 cm long, the usually single main stem erect or strongly ascending, usually developing dense, spreading branches before flowering. Leaves 8–40(–60) mm long, about 1 mm wide. Inflorescences 7–40 cm long, relatively slender, dense and continuous, sometimes arched or nodding toward the tip. Bracts 4–9 mm long, ascending and more or less appressed to the flower. Calyx 2.5–3.5 mm long, with a narrow, horizontal ridge or wing at maturity, becoming papery to somewhat hardened below the ridge, the sepal tips soft and ascending, sometimes somewhat twisted. Fruits 1.5–2.5 mm in diameter. 2n=18. July–October.

Introduced, uncommon and widely scattered, mostly in the St. Louis area (native of Europe, Asia; introduced in the U.S. and adjacent Canada from Montana to Arizona east to Vermont, Kentucky, and Texas). Fallow fields, crop fields, roadsides, railroads, and open, disturbed areas, often in sandy soils.

This species was first reported for Missouri by Mühlenbach (1979). It probably has been undercollected both in the state and elsewhere in the country.