Kelley et al 2014 (Jepson Manual Online), Heil et al 2013
Duration: Annual Nativity: Native Lifeform: Forb/Herb General: Annual herbs, 10-80 cm tall; stems branching above the middle; herbage puberulent or shortly hirsute. Leaves: Alternate; upper leaves sessile and lower leaves on petioles 1-2 cm long; blades linear to oblong, 1- 6 cm long; basal leaves often deciduous. Flowers: Inconspicuous and tiny, on 1-2 mm pedicels and arranged in racemes, each flower subtended by a leaf-like bract; calyx deeply 5-lobed, enlarging to 3 mm long in fruit, the lobes lanceolate and erect in fruit; corolla white to light blue, 2 mm diameter, 5-lobed. Fruits: Nutlets 4 per fruit, each 2-3 mm long, with a single marginal row of prickles, these often swollen and confluent toward the base, forming a cupulate border to the nutlet. Ecology: Found in sunny, usually disturbed sites, roadsides, overgrazed areas, below 8,500 ft (2590 m); flowers March-September. Distribution: Widely distributed throughout much of N. Amer., in every state west of the Mississippi, north to AK and south to n MEX; also in S. America. Notes: A small annual herb, fuzzy all over, with narrow leaves and tiny white to light blue flowers; the fruits are distinctive, being 4 nutlets with marginal, hooked prickles which attach to the socks of passers by. Two varieties are found in Arizona: var. cupulata is a multi-stemmed plant with the nutlet prickles confluent into a swollen, cup-shaped base; var. occidentalis is a single or few-stemmed plant with nutlet prickles slightly confluent at the base but not swollen. Distinguish from L. squarrosa by the nutlets which in that species have at least 2 rows of slender, distinct marginal prickles. L. occidentalis has been considered synonymous with L. redowskii but Heil et al.-s recent San Juan Flora claims that L. redowskii is an Old World species that does not exist in North America. Ethnobotany: Navajo use it to make poultice for insect bites and other skin irritations. Etymology: Lappula is the Latin diminutive for lappa, a bur; occidentalis means of the west. Synonyms: Echinospermum redowskii var. occidentale, Echinospermum occidentale, Lappula echinata var. occidentalis, Lappula redowskii subsp. occidentalis, Lappula redowskii var. occidentalis Editor: SBuckley 2010, FSCoburn 2015, AHazelton 2016
Much like no. 2 [Lappula squarrosa (Retz.) Dumort.]; stem often more spreading hairy and lvs often more softly hairy; nutlets 2-3 mm, the ovate dorsal area surrounded by a single row of prickles. Native of Eurasia and w. N. Amer., intr. as a weed in waste places and along railways e. to Mich., Io., and Mo., and occasionally farther e. Most of our plants, with the marginal prickles distinct to the base, are var. redowskii. (L. occidentalis) Var. cupulata (A. Gray) M. E. Jones, mainly of sw. U.S., also occasionally reaches the w. part of our range. It has the marginal prickles of the nutlets fused to form a cupulate (sometimes much swollen) border. (L. texana)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.