Chenopodium hybridum L.

Jonsell, B., Karlsson, 2005, Chenopodiaceae - Fumariaceae (Chenopodium), Flora Nordica 2, pp. 4-31 : 17-18

10. Chenopodium hybridum L. Figs 2J, 9A

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

- Type: Linnaean Herbarium 313.11 (LINN) lectotype, sei. by Larsen, FI. Cambodge, Laos, Vietnam 24: 95 (1989).

D Hjertebladet Gåsefod. F vaahterasavikka. N hjertemelde.

S lönnmålla.

Therophyte (summer-annual). Sparsely farinose to subglabrous, with slightly unpleasant odour, (10-) 20-100 cm. Stem distinctly angular, yellowish green and usually striped with dirty green (rarely tinged with red), hard, erect, branched mainly in the upper part. Leaves with petiole 1/2 to 2/3 as long as the blade; blade broadly ovate to broadly triangular, (2-)4-15 (-19) cm; base ± cordate to subtruncate; each margin with 1-3 acute or acuminate lobes (or large teeth). Bracts lanceolate, with a pair of basal teeth or sometimes entire.

Inflorescences terminal and axillary, divaricately branched, mono- or dichasial; cymes ± reduced and condensed, glomerules fairly small. Flowers usually bisexual. Tepals 5, connate less than halfway, spreading in fruit, keeled, with membranous margin and obtuse apex; a strong rib visible inside. Stamens 5.

Stigmas 2 or rarely 3, 0.2-0.3 mm. Nut falling with or without the perianth; pericarp firmly adherent to the seed. Seed horizontal, orbicular in outline, 1.6-2 mm; edge rounded; seed-coat black, with large, deep, ± isodiametric pits. - Mid-summer to late summer.

2n=18 (S Sk 2). - [2n=18]

Distribution. Nem-BNem[-SBor]. - Probably archaeophytic in the south, but largely a recent incomer, at least partly brought in with garden plants, and formerly with ballast. - D weakly established archaeophyte; scattered on the islands and in 0Jy; rare in NJy; VJy Tarm 1967, SJy Sønderborg c. 1890, 1986. N mainly in the southeastern lowland, established but declining; also AA Tvedestrand 1889, Ro Stavanger 1875, Ho Osterøy 1930, Ullensvang 1936, Bergen 1971, SF Jølster 1971, MR Stranda 1917. S probably archaeophytic only in the south and southeast; apparently increasing but often ephemeral at individual localities; scattered north to Vg, Ög and Upl (now fairly common in the Stockholm area); rare and usually casual further north: Dls Gunnarsnäs 1908, Vrm Karlstad (several records 1888-1933), Brattfors 1995, Vsm (7 localities) and southeastern Dir (established); along the coast in Gst Gävle several records 1810-1985, His Hudiksvall, Järvsö, Rogsta (all before 1911), Mpd Timrå 1898, 1913, 1961, �ng Härnösand 1932 and Nb Piteå 1908. F ± established in A Kökar, V Turku (and at least formerly in the archipelago) and t/, elsewhere casual; scattered in coastal towns north to KP Kokkola 1950 and OP Oulu 1894, 1901; very rare inland (St Lappi 1959, EH at least 8 municipalities, ES Mikkeli rural community 1964, PH Äänekoski 1938, Viitasaari 1974); mainly with ballast and war-time transports.

Europe, except for the northernmost parts, rare in the Mediterranean and in the southeast; the Caucasus, Siberia, China.

Habitat. Gardens, vegetable-patches, parks, roadsides, waste ground (especially on heaps of soil); very rare as a field weed; earlier often near castles and rectories.

Chenopodium murale

Chenopodium hybridum

Variation. In Europe and North America the C. hybridum aggregate comprises two well-delimited taxa, viz. C. hybridum in Europe and C. simplex (see rare casuals) in North America. In Asia it is represented by several taxa. A specimen from S Upl Sollentuna (Rotebro) 1925 belongs to one of these, having large leaf-blades and large seeds with coarsely rugulose but not pitted seed-coat.

Similar taxa. Chenopodium hybridum is vegetatively ± indistinguishable from the North American C. simplex (rare casual), but clearly different in seed characters.