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Montana Field Guide

Montana Field Guides

Thickleaf Orach - Atriplex dioica
Other Names:  Atriplex subspicata, Atriplex patula var. subspicata

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Native Species

Global Rank: G5
State Rank: SNR
C-value: 3

Agency Status


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General Description
Monoecious annuals with sparsely farinose but still green foliage. Stems erect, 5–30 cm, branched from the base. Leaves sometimes opposite below, the blade 5–30 mm long, ovate to lanceolate, sometimes hastate, with mostly entire margins. Inflorescence terminal, short spikes of glomerules. Male flowers 4- to 5-parted. Female flowers lacking a calyx; pistillate bracts separate to near base. Mature pistillate bracts glabrous to sparsely farinose, ovate, 2–8 mm long, with a spongy, often tuberculate layer at the base. Lesica (2012) places our specimens in Atriplex subspicata, despite the explanation by Welsh (2003; Fl. N. Amer. Vol. 4) that the epithet "dioica" is an older name and thus has priority (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Range Comments
In MT only in Beaverhead and Madison counties in the SW, and again in Valley and McCone counties in the northeast; AB, SK south to CA, NM, KS (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX). The distribution shown by Welsh (2003) for A. dioica is much wider than Lesica's inteprertation of A. subspicata.

Observations in Montana Natural Heritage Program Database
Number of Observations: 11

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Relative Density



(Observations spanning multiple months or years are excluded from time charts)

Drying mud around saline ponds, wetlands; valleys to montane (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

  • Literature Cited AboveLegend:   View Online Publication
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • Jorgensen, H.E. 1970. Ecological aspects of the life history of Agropyron smithii Rydb. in Central Montana, with related effects of selective herbicide treatments of rangeland. Ph.D. Dissertation. Bozeman, MT: Montana State University. 118 p.
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Citation for data on this website:
Thickleaf Orach — Atriplex dioica.  Montana Field Guide.  .  Retrieved on , from