Chenopodium album L.

Jonsell, B., Karlsson, 2005, Chenopodiaceae - Fumariaceae (Chenopodium), Flora Nordica 2, pp. 4-31 : 21-23

15. Chenopodium album L. Figs 3E, H, 10B

Linnaeus, Sp. pi.: 219 (1753).

- Type: Linnaean Herbarium 313.8 (LINN) lectotype, sei. by Brenan, FI. Trop. E. Africa, Chenopodiaceae: 6 (1954).

C. album subsp. densifoliatum A. Ludw. & Aellen (1930) .

C. album subsp. diversifolium Aellen (1928) .

C. album subsp. fallax Aellen (1928) .

C. album subsp. ovatum Aellen (1928) .

D Hvidmelet Gåsefod. F jauhosavikka. Fa hvítur gásafótur.

I hélunjóli. N meldestokk. S svinmålla.

Literature. Dvorak 1991, 1994, Uotila 1972, 1978.

Therophyte (summer-annual). (10-)30-70(-150) cm, ± farinose. Stem subangular to angular, striped with greyish to bluish green, often with purple colour especially in the leaf axils, hard, usually erect, variously branched, often in the basal part. Leaves with petioles usually shorter than the blade; blade fairly thick, dirty greyish green to bluish, in middle leaves rhombic to ovate or lanceolate, sometimes somewhat 3-lobed, (l-)2-5(-7) x (0.7-)l-2.5(~3.5) cm; base ± cuneate; apex fairly acute; margin entire or shallowly and irregularly serrate to dentate by usually fairly obtuse teeth. Bracts narrowly lanceolate; apex acute to acuminate; margin entire.

Chenopodium ficifolium subsp. ficifolium

Chenopodium suecicum

Inflorescences mainly ebracteate, spike-like to panicle-like; glomerules of medium size, fairly closely set, solitary flowers fairly rare. Flowers bisexual or female. Tepals 5, connate halfway, ± farinose, ± keeled or sometimes (especially in terminal flowers) winged, with membranous margin; apex acute. Stamens 5. Stigmas 2(-3), c. 0.4 mm. Nut falling with the perianth; pericarp thin, easily detached. Seed horizontal, almost orbicular in outline (ratio length/width 1.04-1.12), 1.2-1.5 mm; edge fairly acute; seed-coat black, smooth or faintly radially striate, rarely more uneven or reticulate.

Distribution. For Norden, see the varieties.

Almost cosmopolitan, avoiding cold and tropical regions; one of the world’s most widespread weeds.

Variation. Chenopodium album in a wide sense is extremely variable, in size, branching habit, leaf shape, inflorescence habit as well as tepal and seed-coat characters. Some races probably developed together with certain cereals in relatively restricted areas; because of the extensive transport of grain these strains have become mixed and racial differences have been obscured. Much of the variation in morphology and especially in flowering time is correlated with differences in day-length. Generally, under short-day conditions C. album has more dentate leaves and more spike-like inflorescences. Many (but not all) strains of C. album have narrow photoperiodic demands. Most of these strains have their original areas outside Norden; when they grow up in Norden they may, due to the different light climate, be heavily modified and will often not set seed. Therefore, and since the variation in the native areas is largely unknown, many of these deviating plants have to be included in a widely delimited C. album . However, one variety, var. reticulatum , is sufficiently well-known to be recognized taxonomically, and C. missouriense (16), C. borbasioides , C. giganteum , C. probstii and C. purpurascens (rare casuals) are also treated separately, even though their status and delimitation are still partly unsettled.

Hybridization. Hybrids of Chenopodium album var. album are known with C. opulifolium .

Similar taxa. Chenopodium album , especially in the vegetative state or when represented by foreign provenances, is easily confused with several other species. C. missouriense (16) develops very late and has fairly narrow and coarsely serrate leaf-blades and smaller seeds. C. opulifolium (21) has wider, 3-lobed leaf-blades and 3-lobed to entire, mucronate bracts. C. pratericola (\2) is more silvery and has narrower, apiculate leaves. C. suecicum (14) has thinner leaves which are more distinctly 3-lobed and more serrate, toothed bracts, winged tepals and orbicular seeds with rounded edge and coarse ornamentation. C. striatiforme (17), C. strictum (18) and C. virgatum (rare casual) have smaller, more ovate seeds and more elliptic to narrowly truncate, regularly dentate leaves. C. berlandieri (19) and C. hircinum (20) have honeycomb-pitted seeds; the former further deviates by apiculate, fairly few-toothed leaf-blades; C. hircinum (20) as well as C. quinoa and C. acerifolium (rare casuals) have coarsely lobed, more distinctly 3-lobed leaves. - See also C. borbasioides , C. giganteum , C. probstii and C. purpurascens (rare casuals).