5. Atriplex prostrata Boucher ex DC. (spear-scale)

A. patula L. var. hastata (L.) A. Gray

A. patula var. triangularis (Willd.) K.H. Thorne & S.L. Welsh

A. subspicata (Nutt.) Rydb.

A. triangularis Willd.

Pl. 352 e; Map 1515

Stems 15–150 cm tall, prostrate to erect, often climbing over other vegetation, the branches mostly spreading. Leaves alternate, sessile or short- to more commonly long-petiolate. Leaf blades 1–10 cm long, 1.5–4.5 times as long as wide and mostly widest at or near the base, those of the uppermost leaves narrowly lanceolate, but those of most leaves ovate-triangular to triangular, shallowly cordate to truncate or broadly angled at the base, mostly sharply pointed at the tip, mostly with a pair of short basal lobes, these spreading or slightly recurved, the margins otherwise entire or with few to several irregular wavy teeth, silvery gray especially on the undersurface when young, the mealiness often disappearing (at least on the upper surface) by flowering and the surfaces then more or less uniformly green (sometimes reddish-tinged). Staminate flowers axillary and terminal, appearing as elongate spikes with clusters of flowers, these occasionally appearing paniculate. Pistillate flowers intermingled with the staminate ones, all similar, lacking a perianth. Bracts at fruiting fused toward the base, 2–6 mm long, triangular to broadly ovate-triangular, appearing sessile or nearly so, the margins entire, irregular, or with few to several shallow teeth above the base, at maturity becoming more or less uniformly papery or leathery, somewhat spongy-thickened toward the center (appearing slightly inflated), the surfaces occasionally with a pair of narrow, irregular tubercles. Fruits easily separable from the bracts. Seeds usually of 2 kinds, some 1.5–2.5 mm long, brown, dull or shiny; others 1.0–1.8 mm long, black, shiny; in both types, the tip of the radicle (seedling root) positioned below or less commonly alongside the remaining body of the seed. 2n=18. July–September.

Introduced, uncommon and sporadic, mostly in counties adjacent to the Missouri River (native of Europe, Asia, Africa; introduced widely in the U.S. and Canada). Roadsides, railroads, and open, disturbed areas.

The nomenclature and taxonomy of the A. patula polyploid complex require further investigation. The name A. hastata L., which had been used for this taxon in much of the older American literature, was officially rejected from use as an ambiguous epithet at the 1999 International Botanical Congress (Turland, 1996). Many authors have treated A. prostrata as a variety of the closely related A. patula (Steyermark, 1963). The two differ markedly in fruiting bract morphology, those of A. prostrata being ovate-triangular to triangular and somewhat spongy-thickened toward the center (therefore usually appearing slightly inflated), whereas those of A. patula are triangular-ovate to rhombic and lack spongy tissue. However, the two taxa are less distinct vegetatively, which has led to some confusion in determination of immature specimens. In general, all or most of the leaves in A. prostrata are ovate-triangular to triangular, shallowly cordate to truncate or broadly angled at the base, and with a pair of spreading basal lobes. In contrast, the main leaves of plants of A. patula are linear to lanceolate, narrowed or angled at the base, and either unlobed or with the basal lobes ascending. Sterile triploid hybrids between the two have been encountered only rarely (Judd and Ferguson, 1999) and have yet to be found in Missouri, where neither taxon is very common.

Seed dimorphism in a Nebraskan population of this taxon was studied by Ungar (1971), who determined that the thicker-walled black seeds were viable after six years of storage, but they required scarification prior to germination, whereas the thinner-walled yellowish green seeds did not retain their viability but germinated without pretreatment. In the A. patula complex and in other Atriplex species having dimorphic seeds, the larger, lighter-colored seeds with thin walls apparently are adapted for quick restocking of the local population and short-term spread. The smaller, darker seeds with thick walls are adapted for longer-range dispersal and allow the species to survive at sites following periods of hostile environmental conditions.