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perennial rockcress

Habit Perennials; short- to long-lived; (cespitose); sexual; caudex usually not woody. Perennials; long-lived; sexual; caudex woody.
Stems

usually 3–7 per caudex branch, arising from margin of rosette near ground surface, or arising laterally proximal to sterile shoots, 0.4–2.5 dm, glabrous or pubescent proximally, trichomes simple and short-stalked, 2-rayed, 0.1–0.4 mm, glabrous distally.

usually 2–5 per caudex branch, arising laterally proximal to sterile shoots or rosette, often elevated above ground surface on woody base, (1.5–)2–7 dm, densely pubescent proximally, trichomes short-stalked, Y-shaped, 0.2–0.4 mm, often mixed with 3–5-rayed or (rarely) simple ones, usually glabrous distally.

Basal leaves

blade linear to linear-oblanceolate, 1–2.5 mm wide, margins usually entire, rarely denticulate, often ciliate, trichomes (simple), 0.3–0.7 mm, surfaces glabrous or sparsely pubescent, trichomes short-stalked, 2- or 3-rayed, 0.1–0.4 mm.

blade oblanceolate to obovate, 3–15(–20) mm wide, margins dentate, ciliate proximally, trichomes to 1.2 mm, surfaces moderately to densely pubescent, trichomes short-stalked, 3–6-rayed, 0.2–0.4 mm.

Cauline leaves

3–12, not concealing stem;

blade auricles absent, surfaces of distalmost leaves usually glabrous, rarely sparsely pubescent.

4–12(–17), not concealing stem;

blade auricles 0.5–3.5 mm, surfaces of distalmost leaves glabrous.

Racemes

2–12-flowered, unbranched.

16–35-flowered, usually unbranched.

Flowers

ascending-divaricate at anthesis;

sepals glabrous or pubescent;

petals white to pale lavender, 4–5 × 1.5–2 mm, glabrous;

pollen ellipsoid.

ascending at anthesis;

sepals pubescent;

petals white to purplish, 5–9 × 1–1.5 mm, glabrous or sparsely pubescent (occasionally some trichomes abaxially);

pollen ellipsoid.

Fruiting pedicels

divaricate-ascending to horizontal, slightly to strongly recurved, 3–8 mm, glabrous or sparsely pubescent, trichomes (isolated), simple.

usually horizontal, straight or slightly recurved, (6–)10–25 mm, usually glabrous.

Fruits

pendent, not appressed to rachis, not or, rarely, weakly secund, straight, edges parallel, 1.5–3.5 cm × 1.2–2 mm;

valves glabrous;

ovules 28–44 per ovary;

style 0.1–0.4 mm.

widely pendent, not appressed to rachis, not secund, usually curved, edges parallel, (3–)4–7 cm × 1.7–2.1 mm;

valves glabrous;

ovules 60–96 per ovary;

style 0.05–0.4 mm.

Seeds

uniseriate, 0.9–1.2 × 0.6–1 mm;

wing often continuous, 0.07–0.1 mm wide.

uniseriate, 1.1–1.5 × 0.9–1.2 mm;

wing continuous, 0.1–0.2 mm wide.

2n

= 14.

Boechera oxylobula

Boechera perennans

Phenology Flowering May–Jul. Flowering Feb–May.
Habitat Cliffs, rocky slopes, gravelly soil in sagebrush and open conifer forests Rocky slopes and gravelly soil in warm desert, chaparral, low montane habitats
Elevation 2100-3600 m (6900-11800 ft) 200-1700 m (700-5600 ft)
Distribution
from FNA
CO
[BONAP county map]
from FNA
AZ; CA; NM; NV; TX; UT; Mexico (Baja California, Chihuahua, Sonora)
[WildflowerSearch map]
[BONAP county map]
Discussion

Most of the collections assigned here have been called Arabis (Boechera) demissa by other authors (e.g., R. C. Rollins 1993; N. H. Holmgren 2005b). Because the holotype of A. demissa is identical to B. oxylobula in nearly every way (see M. D. Windham and I. A. Al-Shehbaz 2006 for detailed comparison), we treat them as conspecific. Boechera oxylobula is restricted to Garfield, Gunnison, Hinsdale, Lake, Mineral, Park, and Saguache counties in central Colorado. The taxon traditionally treated as A. (Boechera) demissa var. languida is here recognized as an apomictic species of hybrid origin (see Windham and Al-Shehbaz 2007b for detailed comparison).

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

The circumscription of Boechera perennans followed here is much narrower than that adopted by R. C. Rollins (1993). The most significant difference is the removal of Arabis gracilenta. Recent studies (M. D. Windham and Allphin, in prep.) indicate that the latter represents an older name for the species usually called A. (Boechera) selbyi. Although superficially similar, B. perennans is distinguished from B. gracilenta by having stems arising from above ground surface on woody bases, proximal stems with mostly Y-shaped trichomes, strongly dentate margins on basal leaves, and uniseriate seeds. Typically, B. perennans is a sexual diploid largely restricted to the warm deserts of Arizona, California, Nevada, and southern New Mexico. Plants of B. gracilenta are scattered across the Colorado Plateau (northeast of the range of B. perennans) and are apomictic triploids, apparently produced by hybridization between B. fendleri and B. pallidifolia.

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

Source FNA vol. 7, p. 391. FNA vol. 7, p. 396.
Parent taxa Brassicaceae > tribe Boechereae > Boechera 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. 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. williamsii, B. xylopoda, B. yorkii
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. 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. williamsii, B. xylopoda, B. yorkii
Synonyms Arabis oxylobula, Arabis aprica, Arabis demissa, Arabis rugocarpa, B. demissa Arabis perennans, Arabis angulata, Arabis arcuata var. perennans, Arabis eremophila, Arabis recondita
Name authority (Greene) W. A. Weber: Phytologia 51: 370. (1982) (S. Watson) W. A. Weber: Phytologia 51: 370. (1982)
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