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collin's suncress, Collins' rockcress

Habit Perennials; usually short-lived; sexual; caudex not woody. Biennials or perennials; short-lived; apomictic; caudex present or absent.
Stems

usually 1 per caudex branch, arising from center of rosette near ground surface, (1.5–)2.5–8 dm, densely pubescent proximally, trichomes simple and short-stalked, 2-rayed, to 1 mm, sparsely pubescent or glabrous distally.

usually 1 per caudex branch, arising from center of rosette near ground surface, 2.6–7.4(–10.2) dm, densely pubescent proximally, trichomes short-stalked, 4–8-rayed, 0.1–0.5 mm, sometimes mixed with 2- or 3-rayed ones, to 1 mm, usually sparsely pubescent distally, rarely glabrous.

Basal leaves

blade oblanceolate, 1–7 mm wide, margins entire or dentate, ciliate along petiole, trichomes (simple), to 0.7 mm, surfaces moderately to densely pubescent, trichomes short-stalked, 5–8-rayed, 0.15–0.4 mm.

blade oblanceolate, 3–8(–10) mm wide, margins entire or shallowly dentate, ciliate near petiole base, trichomes (simple), to 1 mm, surfaces moderately to densely pubescent, trichomes short-stalked, 4–8-rayed, 0.15–0.4 mm.

Cauline leaves

(8–)15–40, concealing stem proximally;

blade auricles 1–3 mm, surfaces of distalmost leaves usually sparsely pubescent.

22–72, concealing stem proximally;

blade auricles 1–4 mm, surfaces of distalmost leaves sparsely pubescent or glabrous.

Racemes

(15–)30–90-flowered, usually unbranched.

25–112-flowered, usually unbranched.

Flowers

descending to pendent at anthesis;

sepals pubescent;

petals usually white, rarely lavender, 4–6 × 0.8–1.5 mm, glabrous;

pollen ellipsoid.

divaricate-ascending at anthesis;

sepals pubescent;

petals white to lavender, 6–8 × 1–1.5 mm, glabrous;

pollen spheroid.

Fruiting pedicels

reflexed, abruptly recurved at base, otherwise straight, 4–13 mm, glabrous or sparsely pubescent, trichomes usually simple.

divaricate-descending, straight or gently curved, (10–)15–28 mm, usually sparsely pubescent, rarely glabrous, trichomes appressed, branched.

Fruits

strongly reflexed, usually appressed to rachis, rarely somewhat secund, straight, edges parallel, 3.5–6 cm × 0.9–1.5 mm;

valves glabrous;

ovules 70–126 per ovary;

style 0.2–0.5 mm.

pendent, not appressed to rachis, not secund, straight or gently curved, edges parallel, 4.5–6.5 cm × 1.5–3 mm;

valves glabrous;

ovules 100–136 per ovary;

style to 0.2 mm.

Seeds

uniseriate, 1–1.4 × 0.8–1 mm;

wing continuous (rarely absent), to 0.1 mm wide.

biseriate or sub-biseriate, 1–1.4 × 0.9–1 mm;

wing continuous, 0.05–0.15 mm.

2n

= 14.

Boechera collinsii

Boechera goodrichii

Phenology Flowering May–Jun. Flowering Apr–May.
Habitat Rocky and gravelly hillsides, prairies, open woods, floodplains Rocky slopes in sagebrush, pinyon-juniper woodlands, oak thickets
Elevation 600-1400 m (2000-4600 ft) 1300-2300 m (4300-7500 ft)
Distribution
from FNA
ID; MN; MT; ND; NE; SD; WY; AB; MB; QC; SK
[WildflowerSearch map]
[BONAP county map]
from FNA
NV; UT
[BONAP county map]
Discussion

Though often treated as a variety of Arabis (Boechera) holboellii (e.g., R. C. Rollins 1993; G. A. Mulligan 1996), B. collinsii is easily distinguished from that species by having simple and 2-rayed (versus 4–8-rayed) trichomes proximally on stems, and narrower (0.9–1.5 versus 2–2.5 mm) usually non-secund fruits. The two taxa also show allopatric distributions, with B. collinsii found on the North American continent (usually east of the Rocky Mountains) and B. holboellii apparently confined to Greenland.

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

Morphological evidence suggests that Boechera goodrichii is an apomictic species that arose through hybridization between B. gracilipes and B. retrofracta. Some specimens of it originally were identified as Arabis holboellii var. pinetorum (= B. pinetorum), but they are most similar to B. consanguinea (see M. D. Windham and I. A. Al-Shehbaz 2007, 2007b for detailed comparison).

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

Source FNA vol. 7, p. 370. FNA vol. 7, p. 380.
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. 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. 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
Synonyms Arabis collinsii, Arabis holboellii var. collinsii, Arabis retrofracta var. collinsii Arabis goodrichii
Name authority (Fernald) Á. Löve & D. Löve: Taxon 31: 125. (1982) (S. L. Welsh) N. H. Holmgren: in A. Cronquist et al., Intermount. Fl. 2(B): 364. (2005)
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