FNA: Atriplex argentea vs. Atriplex argentea var. rydbergii

Phenology

Flowering summer–fall.

Habitat

Saline, fine-textured substrates derived mainly from Mancos Shale and Morrison formations and clay or silty alluvium, growing in salt desert shrub and floodplain communities

Elevation

1200-2100 m (3900-6900 ft)

Distribution

AZ; CA; CO; ID; KS; MT; ND; NE; NM; NV; OK; OR; SD; TX; UT; WA; WY; AB; BC; MB; SK; Mexico

[WildflowerSearch map]

[BONAP county map]

AZ; CO; NM; UT

Discussion

Varieties 5 (5 in the flora).

Herbarium materials have tended to represent a catchall for annual specimens not readily assignable to other taxa. Indeed, the distinguishing features of the Atriplex argentea complex are shared singly and often in combination with other taxa. Only by use of combinations of features can this taxon be defined. Those features, with much variation, center around the broad, typically ovate to deltoid leaf blades (often definitely 3-veined) and more-or-less compressed, sessile to subsessile (or short stipitate), fruiting bracteoles on which the marginal processes, or teeth, are mainly aligned with the plane compression, and with the faces quite smooth to variously appendaged. Still some specimens are apparently intermediate with other species, especially with the closely allied A. saccaria, with which it is at least partially sympatric.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

In their extreme expression, the leaves of Atriplex argentea var. rydbergii are narrowly elliptic, tapering to both ends, but those extreme forms are connected through a graded series with oval-ovate ones, which tend to maintain the acute-cuneate base, however. The broad-leaved forms are intermediate to var. argentea. Tapering of leaf base to petiole is not restricted to this variety, however. Similar leaf shape occurs rather widely through the species as a whole, but in no place is it so consistently geographically correlated as in the Four Corners region.

H. C. Stutz and G. L. Chu (1997) compared their newly proposed Atriplex pachypoda from southwest Colorado and northwest New Mexico with the A. caput-medusae phase of what is considered herein as A. saccaria var. saccaria. Fruiting bracteole shape, marginal tooth arrangement, and compression are so strikingly similar to those of the A. argentea complex that the relationship with the latter group is apparent. Indeed, the closely contiguous var. rydbergii is nearly identical in all except subtle differences in bracteole shape and the disposition of staminate flowers in a terminal spike or panicle, which is apparently not an entirely constant feature. Arrangement of staminate flowers in terminal spikes appears at once to be a striking feature of var. rydbergii, but the spikes are evanescent, often lacking by fruiting time. And, there are some specimens of that variety in which the staminate flowers were evidently mainly, if not entirely, in axillary glomerules. Because of the similarities to var. rydbergii and the inconsistence of characteristics regarded by its authors as diagnostic, A. pachypoda is herein relegated to synonymy.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Key

1. Plants low, rounded, mainly 1-3(-4.5) dm; fruiting bracteoles sessile or rarely some short stipitate, the appendages mainly acuminate or acute-attenuate; Nevada and adjacent se California, se Oregon	→ 2
1. Plants rather strict and often taller, mainly 2-4(-5) dm; fruiting bracteoles, at least some, short stipitate; appendages acute to less commonly acuminate to attenuate; other distribution	→ 3
2. Leaf blades typically, but not always, constricted to the petiole; herbage merely scurfy, or with elongate trichomes mainly on the fruiting bracteoles; Nevada (except the southern part), and adjacent se California and se Oregon	var. hillmanii
2. Leaf blades typically, if not always, cuneate to a winged petiole or merely sessile base; herbage copiously covered with elongate trichomes throughout, or mostly on the stems and fruiting bracteoles; Nye County, Nevada and adjacent Inyo County, California	var. longitrichoma
3. Leaf blades elliptic to oval, attenuate to a cuneate base; sw Colorado, se Utah, and nw New Mexico	var. rydbergii
3. Leaf blades triangular-ovate to oval, base broadly obtuse to acute or less commonly cuneate; various or other distribution	→ 4
4. Distal leaves short petiolate; proximalmost leaves alternate; plants mostly less than 4 dm; British Columbia to Manitoba, s through Montana, North Dakota, South Dakota, Wyoming, Nebraska, Idaho, Utah, e Nevada, Colorado, w Kansas, ne Arizona, nw New Mexico	var. argentea
4. Distal leaves sessile; proximalmost leaves opposite; plants mostly over 4 dm; California, s Nevada, Arizona, New Mexico, w Oklahoma, w and n Texas	var. mohavensis