Chenopodium suecicum without fruits is often difficult to distinguish from Chenopodium album (15), especially in the north, where lax panicle-like inflorescences and almost entire leaves are common in both species. They differ in seed shape and seed-coat characters, and usually also in stem colour and texture, leaf shape, thickness and colour, inflorescence structure (more leafy with laxer glomerules in )', the tepals are more distinctly keeled in C. suecicum. The difference in ploidy level between and Chenopodium album is reflected in pollen and stomata characters: Chenopodium album has larger pollen with more numerous apertures and larger stomata than . Chenopodium suecicum is sometimes also misdetermined as Chenopodium opulifolium (21); this species has also 3-lobed leaves, but they are broader (about as wide as long) and usually smaller, the bracts are acute to mucronate, the inflorescences are usually ebracteate, the tepals are not winged and the seed surface is fairly smooth.
Habitat. Particularly common, abundant and often dominant as a weed in fields (in D especially with sugar beets), gardens, yards and potato-patches; also roadsides, tips and other waste ground.
Europe: Poland introduced: uncertain degree of naturalisationA
A. Marie Zajac, Adam Zajac & Bogdan Zemanek 2006: Flora Cracoviensis Secunda: p.66
Distribution. Nem-MBor(-NBor). - Archaeophytic. D common, but less so than
Chenopodium album , at least in Sjce, LFM, FyL, NJy and 0Jy; scattered to rare in western Jylland. N fairly common in cultivated areas north to Tr, but in the south less common than C. album', rare in the southwestemmost parts; infrequent and ± ephemeral in the northern coastal areas. S common in southern and eastern lowland parts north to Nb (compared to Chenopodium album less common south of Upl, further north probably more common); also at higher altitudes but less frequent and more often casual. F common (and more common than Chenopodium album ) on the mainland north to EnL and InL where it is fairly rare and usually casual; in A and the southwestern archipelago sporadic, rarer than Chenopodium album . I INo Jôkulsárbrú 1964, Asbyrgi 1964, ISu Hveragerõi 1963.
Eurasia and W North America; from c. 45° to c. 70° N.
Figs 3D, G, 10A Therophyte (summer-annual). 40-80 cm, farinose especially when young. Stem subangular, striped with green, usually soft and without red coloration (autumn plants sometimes with hard stems and with red colour in the leaf axils), erect, usually fairly sparsely branched; branches short, ascending. Leaves with petiole usually c. 2/3 as long as the blade but in lower leaves often as long as the blade; blade thin, on both surfaces pure light green to bluish green, in middle leaves broadly ovate to broadly trullate or triangular, often somewhat 3-lobed, (1-)3-5(-7) x (l-)1.5-3(-4) cm, sometimes as long as wide; base broadly cuneate to truncate; apex fairly obtuse; margin usually closely but unevenly serrate, rarely entire. Bracts petiolate; blade elliptic to lanceolate; margin with a few teeth or rarely entire. Inflorescences usually leafy to near the top, paniclelike, lax; glomerules small and fairly lax, solitary flowers frequent. Flowers bisexual or female. Tepals 5,connate halfway, winged, densely farinose, with membranous margin; apex obtuse to acute. Stamens 5. Stigmas 2 or 3, 0.8-1.1 mm. Nut falling with the perianth; pericarp thin, fairly easily detached. Seed horizontal, orbicular in outline (ratio length/width 0.99-1.03), 1.2-1.6 mm; edge rounded; seed-coat black, shallowly pitted to rugose, often with faint radial striae; epidermal cell walls visible as a reticulum. - Mid-summer to autumn. 2n=l 8 (F EH, EK, EP 2, ES 2, KiL 13, Kn 4, KP 9, Ks 4, OP 2, PeP 8, PH, PK, PS, SoL, St 4, S LL 3, Nb 7, Sk 3, Srm, Vb).-[2n=l8]
Variation. There is a fairly clear, genetically controlled clinal variation from south to north running parallel with the transition from short-day to long-day conditions. The variation is seen in colour (stem more frequently red during short-day conditions), leaf shape, inflorescence branching and seed size. In general, plants in the south have more distinctly 3-lobed and more serrate leaves, more compact and sometimes almost spike-like inflorescences, and smaller seeds. In the north plants with diffusely branched panicle-like inflorescence and almost entire leaves are more common. The variation pattern in C. suecicum is not, as in e.g.
Chenopodium album , blurred by aliens from short-day conditions. Hybridization. Hybrids of Chenopodium suecicum are known with Chenopodium ficifolium subsp. ficifolium .
Polish (Poland): Komosa zielonaB
B. Marie Zajac, Adam Zajac & Bogdan Zemanek 2006: Flora Cracoviensis Secunda: p.66