Amaranthus powellii S. Watson

Raus, Thomas, 2022, Taxonomic, nomenclatural and floristic review of Amaranthaceae of Greece and neighbouring countries, Willdenowia 52 (3), pp. 335-357 : 346

17. Amaranthus powellii S. Watson in Proc. Amer.

Acad. Arts 10: 347. 1875 ≡ Amaranthus retroflexus var.

powellii (S. Watson) B. Boivin in Naturaliste Canad. 93:

641. 1966 ≡ Amaranthus hypochondriacus var. powellii (S. Watson) Pedersen in Monogr. Syst. Bot. Missouri

Bot. Gard. 74: 24. 1999 ≡ Amaranthus hybridus subsp.

powellii (S. Watson) Karlsson in Nordic J. Bot. 20: 519.

2001. – Lectotype (designated by Iamonico 2016a: 525):

North America, U.S.A., Arizona, “from Powell’s Arizona seeds”, 1874, Powell ( US US 00106256).

– “ Amaranthus chlorostachys ” auct. [non Amaranthus chlorostachys Willd., Hist. Amaranth. : 34. 1790].

– “ Amaranthus hybridus ” sensu Tutin & al. (1964: 109) [non Amaranthus hybridus L., Sp. Pl.: 990. 1753].

– “ Amaranthus hypochondriacus ” sensu Greuter & al. (1984: 47) , pro parte [non Amaranthus hypochondriacus L., Sp. Pl.: 991. 1753].

Remarks — Native to SW North America, in the U.S.A. and adjacent regions of Mexico, this species is introduced as a segetal and ruderal weed in warm-temperate regions worldwide ( Bayón 2015: 291). It is at least locally naturalized in Greece, according to Arianoutsou & al. (2010). Considered the putative wild progenitor of its domesticated descendant Amaranthus hypochondriacus , A. powellii has been reported from North and South Pindos, Peloponnisos, Sterea Ellas, North Central, North East and from the Aegean islands of Amorgos, Evvia, Karpathos, Kriti and Samothraki, but the actual distribution may be wider than the present data indicate. That the name A. powellii (and the taxon behind it) does not appear in the Euro+Med PlantBase for Albania, North Macedonia, Bulgaria and Turkey-in-Europe ( Iamonico 2015a) is certainly due to its misleading synonymization with A. hybridus ( Tutin & al. 1964) or A. hypochondriacus ( Greuter & al. 1984). The name A. hybridus has been repeatedly misapplied to A. powellii in Mediterranean basic floras; A. hybridus , however, is generally distinguished by its usually slender, ± patent lateral branches of the inflorescence (vs compact and stiffly erect in A. powellii ).