Acadian orach

Atriplex acadiensis Taschereau, Canad. J. Bot. 50: 1577, figs. 2, 9. 1972

Herbs, erect, 2-4 dm; branches opposite to subopposite or clearly alternate. Stems often red striped, weakly angular. Leaves: petiole 2-15(-25) mm; blade triangular- or lance-hastate, 5-70(-80) × 3-50 mm, ± lobed or dentate to entire, distal ones lanceolate and entire but with short hastate lobes. Flowers in interrupted spicate inflorescences, terminal on main stem and branches, and axillary glomerules loose and widely spaced, with linear or lance-linear bracts. Bracteoles becoming yellow brown in age, sessile or the axillary bracteoles with a stipe 2-5+ mm, ovate-triangular to ovate, 5-7 mm, margin with lateral angles not clearly produced, entire or with a single tooth, apex acuminate, faces smooth, sparsely scurfy, rarely with 2 thin, weak tubercles. Seeds dimorphic: brown, round, 2.5-3.5(-4) mm wide, with radicle basal to subbasal and divaricate most abundant, or black, round, 2-3 mm, with radicle basal and divaricate. 2n = 36.

Flowering late summer-fall. Salt marshes, with Spartina patens; 0-50 m; N.B., N.S., P.E.I., Que.; Maine, Mass.

Historically, Atriplex glabriuscula var. acadiensis has been thought to be closely allied to the ruderal weed, Atriplex patula (with which it is often sympatric, and with which it was synonymized by H. A. Gleason and A. Cronquist 1991). Atriplex glabriuscula var. acadiensis differs from A. patula in being shorter and stockier and having ovate-triangular bracteoles jointed only at the base (not rhombic-triangular with margins united almost to the middle). The taxon, like A. glabriuscula in the broad sense, appears to be confined mainly to native habitats on sea beaches, and apparently is not, or seldom, a ruderal weed as is the case with A. patula. It grows occasionally with the indigenous A. dioica, which has elliptic not round seeds.

Plants examined from New Brunswick typically have at least half of the nodes opposite and opposite branches of unequal size. The plants seem to be closely allied to, and perhaps not always separable from, the largely sympatric Atriplex glabriuscula. I. J. Bassett et al. (1983) indicated that A. acadiensis formed spontaneous hybrids with A. glabriuscula in the Botanic Garden at Manchester England, noting further that these "presumably sterile triploid hybrids exhibited marked heterosis."