Chenopodium pratericola Rydb.

12. Chenopodium pratericola Rydb. Figs 3A, 9C

Rydberg, Bull. Torrey Bot. Club 39: 310 (1912).

- Type: USA, Kansas, Riley Co. 2.VIII. 1895, J.B. Norton 436 (NY) holotype.

C. desiccatum A. Nelson var. leptophylloides (Murr) Wahl (1955).

C. leptophyllum auct., non (Moq.) Nutt, ex S. Watson (1874)

. D Finbladet Gåsefod. F kapealehtisavikka. N amerikamelde.

5 smalmålla.

Literature. Bassett & Crompton 1982, Crawford 1975, Reynolds 6 Crawford 1980.

Therophyte (summer-annual). Up to 1 m, young stems, inflorescences and lower surfaces of leaves usually conspicuously grey-farinose. Stem subangular, striped with green, without red colour, usually erect, branched in the middle and upper parts. Leaves with petiole up to 1(-1.5) cm; blade narrowly elliptic-ovate to narrowly trullate or lanceolate (wider leaves with a lobe-like tooth c. 1/3 from the base on one or both margins), 3-5(-6) x 0.4-1.5(-2.5) cm; base gradually tapering to the petiole; apex obtuse to acute, usually apiculate to mucronate; margin entire.

Inflorescences axillary and terminal, panicle-like; glomerules small. Flowers mostly bisexual. Tepals 5, densely farinose, not covering the fruit at maturity, keeled, with wide membranous margin and ± obtuse apex. Stamens 5. Stigmas 2, c. 0.5 mm. Nut falling with the perianth; pericarp fairly easily detached. Seed horizontal, orbicular in outline, 0.8-1.1 mm; edge rounded; seed-coat black, glossy, rugulose. - Autumn.

[2n=18]

Distribution and habitat. A casual grain and cotton alien mainly recorded from ports, tips and chicken-runs; now very rarely seen. - D first record from 1894; NJy Thisted 1928, �lborg several records 1933-57, ØJy c. 5 localities, latest �rhus 1972, SJy �benr� 1939, FyL 3 localities, latest Svendborg 1961, Sjce 15 localities, mainly in the København area, latest Hvidovre 1975, LFM 4 localities, latest Stubbekøbing 1963. N fairly many records from mills and poultry farms in 0f, Ak, from VA to Ho, and in STSkaun, first in the 1920's; also on ballast in Ak Oslo 1903, 1905 and again in 1969 (from seed bank). S Sk at least 13 localities, latest Landskrona 1968, Bl Karlskrona 1938, Klm Kalmar 1921, Smi Bergunda 1924, Jönköping 1922, 1926, Källeryd 1926, Hl 5 localities, last Hanhals 1959, BhG c. 15 localities 1920 ’s-50’ s, Göteborg 1989, Vg Björketorp 1932, Ög Norrköping 1908, Sund 1930, Srm Eskilstuna 1999, Nyköping several records 1906-21 (with cotton), Nacka several records 1894- 1932, Salem 1919, Upl several localities around Stockholm and Uppsala, last 1952, Järlåsa 1923, Norrtälje 1925, Gst Gävle several records 1919-29, His Hudiksvall 1953, Mpd Skön 1911, Sundsvall 1922,7L Abisko 1927. A report from Vrm (Anonymous 1994) is due to misidentification. F first recorded 1904 but mainly in the period 1948-55; later on infrequent; c. 50 records from c. 20 places north to OP, more than half from Helsinki and Turku. I INo Akureyri 1950.

North America; a fairly frequent incomer in Europe.

Biology. In contrast to many other casual Chenopodium species apparently sometimes setting seed in Norden, especially in the southern parts.

Taxonomy. Chenopodium pratericola is the most widespread member of a critical North American group of narrow-leaved species. There are different views on how this group is best treated taxonomically. In the narrow sense G pratericola has fairly large, thin leaf-blades which are fairly sparsely farinose on the upper surface and have 1 or 2 prominent, lobe-like teeth in the basal half, and moderately strongly keeled tepals. The closely related G desiccatum (less weedy, with a more limited distribution in W North America) has thicker, more farinose, entire leaves and more strongly keeled tepals. Many Nordic specimens (especially small ones) have extremely narrow leaves without teeth; there are plants which are very farinose on stems, leaves and tepals as well as ones which are only a little farinose. Possibly different taxa have occurred in Norden, but because the specimens are usually in vegetative or early flowering state they cannot be determined with certainty. For this reason G pratericola must be taken in a wide sense here.

Nomenclatural confusion has also occurred; the name C. leptophyllum has often been used for the species occurring in Norden, but belongs to a different species which is also related to C. pratericola. - If G desiccatum and C. pratericola prove to be conspecific the oldest name for the taxon is C desiccatum A. Nelson from 1902.

Similar taxa. Chenopodium pratericola is similar to narrow-leaved forms of the following species: G album (15), C striatiforme (17), C strictum (18) and C. virgatum (rare casual); however, these species are less silvery, the leaf apex is obtuse to acute (sometimes mucronate but not apiculate), and the stem is often red-tinged. Further, in these taxa the seeds are either broadly ovate in outline or larger (C. album).