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arching rockcress, elegant rockcress

Graham's rockcress, Graham's suncress

Habit Perennials; usually long-lived; sexual; caudex often woody (well-developed). Biennials or perennials; short-lived; apomictic; caudex present or absent.
Stems

usually 1 per caudex branch, arising from center of rosette, elevated on woody base or from ground surface, (2–)3–8 dm, densely pubescent proximally, trichomes short-stalked, 2-rayed and simple, to 1 mm, pubescent distally.

usually 1 per caudex branch, arising from center of rosette near ground surface, (1.2–)2–12 dm, glabrous or pubescent proximally, trichomes simple and sessile or subsessile, 2 or 3(–6)-rayed, to 1 mm, glabrous distally.

Basal leaves

blade linear to oblanceolate, 2–7(–12) mm wide, margins usually entire, rarely denticulate, ciliate along petiole, trichomes to 1.5 mm, surfaces densely pubescent, trichomes usually short-stalked, 2–5-rayed (rarely some simple), 0.4–0.8 mm.

blade oblanceolate, 1.5–10(–20) mm wide, margins entire or dentate, ciliate proximally, trichomes (simple), to 1 mm, surfaces sparsely to densely pubescent, trichomes sessile or subsessile, 2–4(–7)-rayed, 0.2–0.6 mm.

Cauline leaves

10–30(–45), often concealing stem proximally;

blade auricles 2–5(–6) mm, surfaces of distalmost leaves pubescent.

(10–)13–52, often concealing stem proximally;

blade auricles 1–5 mm, surfaces of distalmost leaves glabrous.

Racemes

12–50(–70)-flowered, usually unbranched.

16–88-flowered, usually unbranched.

Flowers

ascending at anthesis;

sepals pubescent;

petals purple, 9–14 × 2–4 mm, glabrous or sparsely pubescent (trichomes abaxially);

pollen ellipsoid.

divaricate at anthesis;

sepals glabrous or pubescent;

petals usually white, rarely lavender, 5.5–8 × 1–2 mm, glabrous;

pollen spheroid.

Fruiting pedicels

usually divaricate-ascending, rarely horizontal, gently recurved or straight, 8–22 mm, pubescent, trichomes subappressed, 2–4-rayed.

divaricate-ascending to descending, usually gently curved downward, rarely straight, 5–22(–30) mm, glabrous.

Fruits

usually divaricate-ascending, rarely horizontal, not appressed to rachis, not secund, usually curved, edges parallel, (6–)8–13 cm × 1.5–2.2 mm;

valves glabrous or trichomes relatively few, scattered;

ovules 90–250 per ovary;

style 0.01–0.5 mm.

divaricate-ascending to pendent, not appressed to rachis, not secund, straight or slightly curved, edges parallel, 3.5–9 cm × 1–1.8 mm;

valves glabrous;

ovules 84–146 per ovary;

style 0.05–0.5 mm.

Seeds

uniseriate or sub-biseriate, 1.5–1.7 × 1–1.2 mm;

wing continuous, 0.1–0.2 mm wide.

uniseriate to sub-biseriate, 1–1.8 × 0.8–1.2 mm;

wing continuous, 0.1–0.25 mm wide.

2n

= 21.

Boechera arcuata

Boechera grahamii

Phenology Flowering Mar–Jun. Flowering May–Aug.
Habitat Rocky hillsides and cliffs in pine forests and chaparral Rocky slopes and sandy soil in prairies and open forests
Elevation 300-1800 m (1000-5900 ft) 100-3200 m (300-10500 ft)
Distribution
from FNA
CA
[WildflowerSearch map]
[BONAP county map]
from FNA
AK; CO; MI; MN; MT; ND; NY; SD; VT; WA; WI; WY; AB; BC; MB; NT; ON; QC; SK; YT
[WildflowerSearch map]
[BONAP county map]
Discussion

Although usually treated as a variety of Arabis (Boechera) sparsiflora (e.g., R. C. Rollins 1993), B. arcuata is easily distinguished from that species by having rachises and fruiting pedicels pubescent with subappressed, 2–4-rayed trichomes and a geographic range limited to southern and western California. By contrast, B. sparsiflora has rachises and fruiting pedicels with spreading, usually simple trichomes (sometimes glabrescent) and an allopatric distribution north and east of the Sierra Nevada.

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

Morphological evidence suggests that Boechera grahamii is an apomictic species that arose through hybridization between B. collinsii and B. stricta. Previous authors have assigned these specimens to Arabis (Boechera) divaricarpa (see M. D. Windham and I. A. Al-Shehbaz 2007b for detailed comparison); if these taxa are treated as conspecific, the name B. grahamii has priority.

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

Source FNA vol. 7, p. 365. FNA vol. 7, p. 382.
Parent taxa Brassicaceae > tribe Boechereae > Boechera Brassicaceae > tribe Boechereae > Boechera
Sibling taxa
B. acutina, 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. 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. 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. williamsii, B. xylopoda, B. yorkii
Synonyms Streptanthus arcuatus, Arabis holboellii var. arcuata, Arabis maxima, Arabis sparsiflora var. arcuata Turritis grahamii, Arabis boivinii, Arabis bourgovii, Arabis confinis, Arabis confinis var. brachycarpa, Arabis dacotica, Arabis divaricarpa var. dacotica, Arabis divaricarpa var. hemicylindrica, Arabis divaricarpa var. stenocarpa, Arabis drummondii var. brachycarpa, Arabis holboellii var. brachycarpa, B. brachycarpa, Turritis brachycarpa
Name authority (Nuttall) Windham & Al-Shehbaz: Harvard Pap. Bot. 11: 64. (2006) (Lehmann) Windham & Al-Shehbaz: Harvard Pap. Bot. 12: 241. (2007)
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