9. Chenopodium glaucum L. (oak-leaved goosefoot)

Pl. 353 a–c; Map 1529

Plants annual, without an odor. Stems 5–40 cm long, prostrate to erect, unbranched or more commonly much-branched from near the base, glabrous or sparsely white-mealy, often strongly reddish-tinged or reddish-striped. Leaves short- to long-petiolate. Leaf blades 0.5–4.0 cm long, mostly 1–3 times as long as wide, lanceolate to oblong or ovate, bluntly pointed at the tip, angled at the base, herbaceous in texture, the margins entire, wavy or with few to several sharp or blunt, irregular teeth, the most basal ones occasionally deeper and appearing as a pair of shallow lobes, the upper surface glabrous or nearly so, the undersurface densely white-mealy. Venation noticeably branched (best observed from upper surface), with 1 or more commonly 3 main veins. Inflorescences axillary and terminal, consisting of small clusters of flowers, these sometimes arranged into spikes, the terminal ones sometimes grouped into small panicles. Flowers not all maturing at the same time. Calyx 3–5-lobed nearly to the base, shorter than and only partially covering the fruit at maturity, the lobes 0.4–0.6 mm long, oblong to oblong-obovate, rounded to bluntly pointed at the tip, flat to somewhat pouched dorsally, glabrous. Stamens 3–5. Stigmas 2, minute. Fruits 0.6–1.0 mm long, ovoid to depressed-ovoid, the seeds mostly positioned mostly horizontally, but a few vertically oriented seeds also present, the wall thin, membranous, and somewhat translucent, smooth, easily separated from the seed. Seeds reddish brown to dark brown, shiny, smooth or finely roughened, rounded along the rim. 2n=18. July–November.

Introduced, uncommon and local in northwestern Missouri and the city of St. Louis (native of Europe; introduced widely in the U.S. and Canada). Margins of lakes; also railroads and open, disturbed areas.

As noted by McGregor (1986a), variation within the C. glaucum complex requires further study. The present treatment tentatively accepts two varieties.