Dalea flavescens
Rupert C. Barneby
34. Dalea flavescens (Watson) Welsh
(Plate LII)
Perennial from a thick woody root and shortly forked caudex, (2.5) 3-4.5 dm tall, either pilosulous throughout with weak spreading and ascending hairs up to 0.35-0.8 (1.2) mm long, or the stems glabrous and only the foliage silky-pilosulous, or glabrous to the spikes, the several erect, incurved-ascending, or diffuse, ribbed, pale green, sparsely but prominently livid-tuberculate stems leafy in the lower 1/2-2/3, simple except for short spurs in most leaf-axils (a few of these exceptionally developed and terminating in a small flower-spike), passing upward into a stout monocephalous peduncle, the foliage gray-green or pallid and subglaucescent, the thick-textured leaflets smooth above, punctate or verruculose beneath; leaf-spurs 0.2-1 mm long; stipules linear-lanceolate or narrowly linear, becoming stiff and fragile, 1-3.5 (4.5) mm long; intrapetiolular glands 2, small; post-petiolular glands large, obtuse; leaves petioled, the main cauline ones (2) 2.5-4 (4.5) cm long, with verrucose rachis and 2-3 pairs of oblong-obovate to narrowly oblong-elliptic, obtuse, emarginate, or obtuse and gland-mucronate, usually ± folded and backwardly arched leaflets up to 7-17 (19) mm long, the terminal one either stalked or sessile, commonly at least a trifle longer than the last pair; peduncles (4) 7-20 (25) cm long; spikes ovoid-oblong to oblong- cylindroid, dense and softly conelike, without petals 8.5-12 (13) mm diam, the flowers (pressed) presenting 5-7 ranks on each side of spike, the pilosulous axis becoming (1) 1.5-7 (10) cm long; bracts held fast between the calyces and falling only with the
fruit, subhomomorphic except the lowest slightly firmer and broader, the interfloral ones 2.5-5.5 (6.5) mm long, obovate- to oblanceolate-acuminate, below middle folded and scarious-margined, the blade flat or shallowly concave, green or castaneous, sometimes gland-sprinkled and -margined, contracted distally into a livid-castaneous, sometimes glabrescent tip, otherwise densely pilosulous dorsally, glabrous within; calyx(3) 3.3-4.7 (5.2) mm long, pilosulous (especially on and within the teeth) with fine, spreading-ascending hairs up to 0.35-0.95 mm long, the ovoid tube (2) 2.2-2.8 mm long, deeply recessed behind the banner, the ribs slender, scarcely prominent externally, the submembranous, pallid or castaneous-flecked intervals glandless or charged with 1-3 small colorless glands, the connivent teeth of subequal length, the dorsal one narrowest, lanceolate, (1) 1.2-2.6 (2.9) mm long, their plane tips either green or castaneous, sometimes charged with a few small blister-glands on back or margins; petals white when fresh (sometimes drying ochroleucous), the epistemonous ones inserted at the separation of the filaments (the dorsal pair often a trifle lower than the lateral); banner 5-7.4 (8.4) mm long, the claw 2.6-4.5 mm, the erect, ovate- deltate or broadly ovate, shallowly hooded, emarginate or irregularly crenate blade 2.6-4.2 (4.5) mm long, 2.2-3.9 (4.5) mm wide; epistemonous petals 3.8-4.6 (6.3) mm long, the claw 1-1.6 (1.8) mm, the oblong-oblanceolate, subtruncate or emarginate blades cuneately or subtruncately contracted at base, 3-3.9 (4.5) mm long, 0.9 1.6-(1.9) mm wide; androecium (5.5) 6.2-10 (12.7) mm long, the column (2) 2.7-3.8 (4) mm, the free filaments up to 3.4-6.2 (8.7) mm long, the connective gland-tipped, the anthers yellow, 0.9-1.6 mm long; pod obliquely obovoid, 3.1-3.7 mm long, the ventral suture shortest, the style-base latero-terminal or lateral, the strongly convex dorsal suture slenderly carinate around the prow, the valves hyaline in lower thence thinly papery, minutely gland-sprinkled, densely pilosulous; seed 2.1-2.4 mm long.— Collections: 16 (v).
Gullied sandy-clay benches of canyons, sandy pockets of rimrock, and sand-talus under cliffs, sometimes on dunes, associated with red or white sandstones, locally abundant in scattered stations in the canyonlands of the Colorado Plateau in s.-e. Utah, from San Rafael Swell in Emery County e. to Arches National Monument in Grand County, s. to Monument Valley in San Juan County and there crossing s. just into Arizona, and along the Colorado River itself to Rainbow Bridge and Glen Canyon in extreme e. Kane County; cf. Wemple, 1970, map 10. — Flowering May and June. Representative: Utah: Maguire 18,481 (NY, UC); Cronquist & Holmgren 9246 (NY, widely distributed); Welsh & Moore 7130 (NY); Ripley & Barneby 8669 (CAS, NY); Barneby 14,438 (CAS, GH, DAO, IA, MEXU, NY, UC, US), 15,011 (CAS, IA, NY, US), 15,022 (NY).
Dalea flavescens (Wats.) Welsh, Great Basin Nat. 31 (2): 90 (in diagnosi D. epicae). 1871, based on Petalostemon flavescens (yellowing, of the white petals when dried) Wats., Amer. Nat. 7: 299. 1873. — "Kanab [but probably further to the n.-e. in the Colorado Basin], Southern Utah (Mrs. E. P. Thompson)..." — Holotypus, GH! — Kuhniastera flavescens (Wats.) O. Kze., Rev. Gen. 192. 1891.
Dalea epica (of the heroic pioneers who crossed the Colorado River in 1880 near the type-station) Welsh, Great Basin Nat. 31 (2): 90, fig. 1. 1971.-"Utah: San Juan Co., Plateau, ca 10 miles east of Halls Crossing...S. L. Welsh 5205, 30 April 1966..." - Holotypus, BRY! = NY Neg. 8230; isotypus, NY! paratypus (Welsh 9816), NY!
In habit and foliage D. flavescens resembles D. searlsiae and D. ornata but differs from both in its white petals, from the first in its permanently condensed flower-spike, and from the second in its firmer, strongly asymmetric calyx-tube. Wemple (1970, quoting an earlier opinion of M. E. Jones) comments on the specially close relationship between D. flavescens and the vicariant D. searlsiae, which have essentially the same flower-structure. The range of D. searlsiae extends to the eastern margin of the Colorado canyonlands on the Pahria and Escalante Rivers, but is not known to impinge on that of D. flavescens.
Dissection of the Colorado Plateau into a maze of troughlike canyons, connected only by the main north-south waterway of the Colorado River, effectively cuts up the range of species endemic to the lower elevations into many discrete populations which may lie only a few miles apart by direct airline yet remain insulated from each other. This circumstance has apparently worked in concert with the variability inherent in the prairie-clovers to produce within D. flavescens as here understood a number of recognizable but taxonomically insignificant variants. These differ among themselves in pubescence, length and diameter of the spike, and length of calyx, petals and androecium. Most commonly, and at all known peripheral stations of the species, the foliage is more or less pilosulous, but hairy leaves may be combined with either hairy or hairless stems. In White Canyon below Natural Bridges, a form glabrous to the spikes is found close to the pubescent type, in this case not otherwise different; the variation is in this instance of the same sort as occurs in D. searlsiae and D. purpurea. Variation in flower-size is complicated by the fact that the various parts fluctuate independently. This is true especially of the free filaments, which (whatever the petal-size) may raise the anthers only half-way to the petal-tips or far beyond them. The three flowers illustrated (Pl. LII, figs. 1, 3a, 8) represent three of several known combinations. An average flower of D. flavescens has the calyx ± 3.5 mm long and a spike, either long and cylindroid or short and headlike, about 1 cm diam. An exceptionally large-flowered population from the Colorado rim east of Hall’s Crossing of the Colorado in San Juan County, with calyx ± 5.6 mm long, long-tipped bracts to match, and a long fat spike up to 12-13 mm diameter when shorn of petals and stamens, has been described as D. epica; it is linked to the average sort by a collection from across the river in Garfield County (Barneby 15,022) with shorter but only slightly narrower spike. The type-population of D. epica is notable for the coincidence of pubescent foliage, densely pubescent interfloral bracts, and large epistemonous petals, a little over 6 mm long. Downstream near Rainbow Bridge a more remarkable variant (Holmgren & Goddard 9990, mentioned by Wemple, 1970, p. 65, and illustrated herewith, Pl. LII, fig. 8) combines the large calyx and long epistemonous petals of D. epica with glabrous foliage and conspicuously gland- pustulate, thinly pubescent bracts and calyx-teeth. Again a few miles downstream, near Glen Canyon City, the species is represented by a pubescent, small-flowered population hardly different from that in White Canyon already mentioned.
References: [Article] Barneby, Rupert C. 1977. Daleae Imagines, an illustrated revision of Errazurizia Philippi, Psorothamnus Rydberg, Marine Liebmann, and Dalea Lucanus emen. Barneby, including all species of Leguminosae tribe Amorpheae Borissova ever referred to Dalea. Mem. New York Bot. Gard. 27: 1-892.Multimedia:
