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Habit Perennials; short-lived; sexual; caudex not woody.
Stems

usually 1 per caudex branch, arising from center of rosette near ground surface, 0.7–2.2 dm, glabrous throughout.

Basal leaves

blade oblanceolate, 1–2 mm wide, margins entire, ciliate near petiole base, trichomes (simple), to 0.4 mm, surfaces sparsely to densely pubescent, trichomes short-stalked, 4–8-rayed, 0.03–0.1 mm.

Cauline leaves

6–11, sometimes concealing stem proximally;

blade auricles to 0.5 mm, surfaces of distalmost leaves glabrous.

Racemes

5–17-flowered, unbranched.

Flowers

erect at anthesis;

sepals glabrous;

petals white, 3–4 × 0.5–0.8 mm, glabrous;

pollen ellipsoid.

Fruiting pedicels

erect, straight, 2–4(–7) mm, glabrous.

Fruits

erect, usually appressed to rachis, not secund, straight, edges parallel, 2–3.5 cm × 2.2–2.5 mm;

valves glabrous;

ovules 60–96 per ovary;

style 0.05–0.2 mm.

Seeds

sub-biseriate, 0.7–0.9 × 0.5–0.6 mm, not winged or minutely winged distally.

Boechera williamsii

Phenology Flowering May–Jun.
Habitat Gravelly soil in sagebrush-grassland communities
Elevation 2300-2800 m (7500-9200 ft)
Distribution
from FNA
WY
[BONAP county map]
Discussion

Boechera williamsii is distinguished from all other sexual species of the genus by its combination of relatively short (3–4 mm), white petals, minute, 4–8-rayed trichomes on basal leaves, erect, appressed fruits, and relatively small, wingless seeds. It is known only from Fremont and Sublette counties in west-central Wyoming. The taxon traditionally treated as Arabis (Boechera) williamsii var. saximontana is here recognized as an apomictic species of hybrid origin (see M. D. Windham and I. A. Al-Shehbaz 2007b for detailed comparison).

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

Source FNA vol. 7, p. 411.
Parent taxa Brassicaceae > tribe Boechereae > Boechera
Sibling taxa
B. acutina, B. arcuata, B. atrorubens, B. bodiensis, B. breweri, B. burkii, B. calderi, B. californica, B. canadensis, B. cascadensis, B. cobrensis, B. collinsii, B. consanguinea, B. constancei, B. covillei, B. crandallii, B. cusickii, B. davidsonii, B. dentata, B. depauperata, B. dispar, B. divaricarpa, B. drepanoloba, B. duchesnensis, B. elkoensis, B. evadens, B. falcatoria, B. falcifructa, B. fecunda, B. fendleri, B. fernaldiana, B. formosa, B. fructicosa, B. glareosa, B. glaucovalvula, B. goodrichii, B. gracilenta, B. gracilipes, B. grahamii, B. gunnisoniana, B. harrisonii, B. hastatula, B. hoffmannii, B. holboellii, B. horizontalis, B. howellii, B. inyoensis, B. johnstonii, B. koehleri, B. laevigata, B. languida, B. lasiocarpa, B. lemmonii, B. lignifera, B. lincolnensis, B. lyallii, B. macounii, B. microphylla, B. missouriensis, B. nevadensis, B. ophira, B. oxylobula, B. paddoensis, B. pallidifolia, B. parishii, B. pauciflora, B. paupercula, B. peirsonii, B. pendulina, B. pendulocarpa, B. perennans, B. perstellata, B. pinetorum, B. pinzliae, B. platysperma, B. polyantha, B. porphyrea, B. pratincola, B. puberula, B. pulchra, B. pusilla, B. pygmaea, B. quebecensis, B. rectissima, B. repanda, B. retrofracta, B. rigidissima, B. rollei, B. rollinsiorum, B. rubicundula, B. saximontana, B. schistacea, B. serotina, B. serpenticola, B. shevockii, B. shockleyi, B. sparsiflora, B. spatifolia, B. stricta, B. subpinnatifida, B. suffrutescens, B. texana, B. tiehmii, B. tularensis, B. ultra-alsa, B. villosa, B. xylopoda, B. yorkii
Synonyms Arabis williamsii
Name authority (Rollins) Dorn: Vasc. Pl. Wyoming ed. 3, 376. (2001)
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