Chenopodiastrum is a small genus of non-aromatic annual herbaceous flowering plants in the family Amaranthaceae (order Caryophyllales). The genus was formally described in 2012 by Suzy Fuentes-Bazan, Pertti Uotila, and Thomas Borsch, when phylogenetic analysis revealed that retaining these species within Chenopodium would have rendered that genus polyphyletic. Chenopodiastrum is placed in tribe Atripliceae, the same tribe as Chenopodium.
Plants in this genus are typically glabrescent herbs: young growth bears conspicuous vesicular trichomes that later collapse and fall away, leaving the surface nearly hairless at maturity. Stems grow erect with lateral branches. The alternate leaves are petiolate with thickish blades ranging from triangular and rhombic-ovate to lanceolate, with margins that may be irregularly dentate, lobed, or pinnatifid with narrow dentate lobes.
Flowers are small and borne in dense glomerules arranged in axillary and terminal spike-like or paniculate inflorescences. Each flower is bisexual or pistillate and bears 5 basally connate perianth segments with a prominent keel near the apex and a strong midrib visible from the inside, 5 stamens, and an ovary topped by 2 stigmas. The membranous pericarp adheres firmly to the seed. Seeds are horizontally oriented, lenticular, and typically black with a prominently pitted, rugulose, or nearly smooth surface.
The genus comprises approximately 5–7 species distributed across Eurasia, North Africa, and North America, with individual species ranging from the Canary Islands and Mediterranean Europe through Central Asia and China to the North American continent.
Etymology
The genus name Chenopodiastrum is formed from Chenopodium — the closely related goosefoot genus (itself from Greek chen, goose, and pous/podos, foot, referring to the leaf shape) — plus the Latin suffix -astrum, indicating resemblance or a related but distinct group. The name thus signals the genus's close affinity with Chenopodium from which it was segregated.
Distribution
Species of Chenopodiastrum occur in both the Old World and North America. The range spans from the Canary Islands and Mediterranean Europe through North Africa, Southwest Asia, Central Asia, and the Indian subcontinent to China, with one species (C. simplex) native to North America. Some members, such as C. murale, are widespread weedy plants that have naturalized well beyond their native ranges.
Taxonomy Notes
Chenopodiastrum was erected in 2012 by Fuentes-Bazan, Uotila & Borsch (Willdenowia 42, p. 14) as part of a broader phylogeny-based reclassification of Chenopodium sensu lato and a tribal rearrangement of Chenopodioideae within Chenopodiaceae (now subsumed in Amaranthaceae). Without separation, Chenopodium would have been polyphyletic. The genus belongs to tribe Atripliceae. GBIF places the family as Chenopodiaceae (a name still in use in some classifications) within order Caryophyllales.
