Herbs, annual; taproot tapered, soft or ± woody. Stems erect or ascending, unbranched when small to branched ca. 1-5 times throughout, 10-60 dm, minutely puberulent to glandular-pubescent basally, usually glandular-pubescent, sometimes minutely puberulent or glabrous distally. Leaves mostly in basal 1/2; larger leaves with petiole 2-22 mm, blade oval, ovate, oblong, or lanceolate, 12-37 × 5-20 mm (distal leaves smaller, proportionately narrower), adaxial surface glabrate, sparsely puberulent, sometimes glandular-pubescent, abaxial surface not noticeably to prominently paler than adaxial, glabrate or occasionally glandular-pubescent, both surfaces usually punctate with dark cells, base round to obtuse, margins sinuate to sinuate-crisped, apex acute, obtuse, or round. Inflorescences terminal, branched ca. 1-4 times unequally, without sticky internodal bands; branches strongly ascending, terminating in compact, capitate or subcapitate flower clusters, axis 0-2.5 mm. Flowers: pedicel 0.8-2.5 mm; bracts at base of perianth persistent, 1-3, ovate to obovate, 2.5-4 mm, apex apiculate; perianth whitish to pale pink, funnelform beyond constriction, 2.5-4 mm; stamens 3-4(-5), well exserted. Fruits 3-9 per cluster, straw colored to grayish tan, broadly obovoid, 2.3-3 × 1.3-1.7 mm (l/w: 1.6-2.1), apex round or broadly obtuse, glabrous; ribs 5, acute, smooth; sulci 2-2.5 times as wide as base of ribs, not or shallowly rugose, lightly papillate.
Flowering late summer. Sandy soils in open arid grasslands, among open shrubs or oaks, pinyon pines, juniper [thornscrub]; [200-]1300-1800 m; Ariz., N.Mex.; Mexico (Chihuahua, Sonora).
The inclusion of Boerhavia purpurascens in recent Texas floras is based upon misidentified Mirabilis species (C. F. Reed 1969).
FNA 2004, Kearney and Peebles 1969
Duration: Annual Nativity: Native Lifeform: Forb/Herb General: Annual herbs, to 60 cm tall, from a soft or woody taproot; stems erect or ascending, unbranched on small plants and branched 1-5 times throughout on larger plants; herbage puberulent to glandular-pubescent. Leaves: Opposite, on petioles 2-20 mm long; blades ovate to lanceolate, 1-4 cm long and 5-20 mm wide, with sinuate and sometimes crisped margins; leaf surfaces usually punctate with dark cells, especially the leaves near the base of the plant; leaf undersides usually a bit paler than upper leaf surfaces. Flowers: Small, pink to purple, in small dense clusters at branch tips, the clusters arranged in panicles that branch 1-4 times, the branches unequally-lengthed and covered with gland-tipped hairs; sepals appearing petal-like, 3-4 mm long, fused into a funnel-shape, whitish to pale pink or purple; petals absent. Fruits: Achenes in clusters of 3-9, straw-colored to grayish-tan, 2-3 mm long and 1-2 mm wide, broadly obovoid with a round blunt tip and 5 smooth longitudinal ribs. Also look for the flower stalks which are covered with gland-tipped hairs. Ecology: Found on limestone or sandy soils, in open arid grasslands, or among shrubs, oaks, pinyon pines, chapparal, or junipers; from 700-6,000 ft (213-1829 m); flowers in late summer. Distribution: s AZ and s NM; south to MEX Notes: This pretty annual spiderling has small but showy pink to purple flowers (showy relative to many in this genus). The fruits have 5 narrow ridges and open, broad furrows between the ridges. Ethnobotany: Unknown, but other species in the genus have uses. Etymology: Boerhavia is named after Dutch botanist Hermann Boerhaave (1668-1738); purpurascens means becoming purple or purplish. Synonyms: None Editor: LCrumbacher 2012, AHazelton 2017