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Key to families | Table of families and genera

Specimen numbers are hyperlinked to records in the Consortium of California Herbaria data view where possible. Taxa are hyperlinked to entries in the Jepson Interchange via the "[Online Interchange]" link.

 

BOECHERA ROCKCRESS

Michael D. Windham & Ihsan A. Al-Shehbaz


Perennial herb (biennial); caudex simple or branched, persistent leaf bases generally absent; rosetted or not; rosette at ground surface or elevated on woody base; hairs simple or 2–14-rayed, stalked or sessile. Stem: simple or branched, leafy. Leaf: basal petioled, simple, generally entire or dentate, generally hairy; cauline sessile, base generally lobed, entire or dentate. Inflorescence: generally elongated. Flower: sepals bases generally not sac-like; petals generally white, lavender, or purple, claw present or 0; pollen ellipsoid in sexual plants, spheric in plants with asexual seeds. Fruit: silique, dehiscent, generally linear, edges generally parallel, unsegmented, flat parallel to septum; stigma entire or 2-lobed. Seed: in 1 or 2 rows, winged or not.
110+ species: temperate North America, Russian Far East. (T.W. Boecher, Danish cytogeneticist, 1909–1983) [Windham & Al-Shehbaz 2006–2007 Harvard Pap Bot 11:61–88, 11:257–274, 12:235–257] Some species with both fertile & sterile stems. Previously included in Arabis, but the 2 genera in different tribes. Boechera horizontalis (Greene) Windham & Al-Shehbaz [Arabis suffrutescens S. Watson var. horizontalis (Greene) Rollins] not in California.
Unabridged references: [Al-Shehbaz 2003 Novon 13:381–391]
Unabridged note: Hybrids with spheric pollen and morphological intermediacy generally more common than sexual diploids (with ellipsoid pollen).

Key to Boechera

1. Fruit, generally ovary hairy

2. Fruit pedicel < 2.5 mm; petals ± yellow to brick-red ..... B. yorkii

2' Fruit pedicel > 2.5 mm; petals purple, lavender, or white

3. Fruit pedicel base generally abruptly recurved; fruit generally appressed to inflorescence axis

4. Stems elevated above ground surface on woody base; petals 9–16 mm; fruit 2.5–4 mm wide; seeds 1.7–2.8 mm ..... B. pulchra

4' Stems from ± ground surface, from non-woody caudex; petals 4–8 mm; fruit 0.9–1.8 mm wide; seeds 1–1.4 mm ..... B. retrofracta (3)

3' Fruit pedicel base not abruptly recurved; fruit generally not appressed to inflorescence axis

5. Proximal stems with simple and 2-rayed hairs only

6. Fruit pedicel with branched hairs only ..... B. arcuata (2)

6' Fruit pedicel with generally simple hairs ..... B. breweri subsp. breweri (2)

5' Proximal stems with at least some 3–12-rayed hairs

7. Petals generally < 9 mm

8. Stem proximally with 7–12-rayed hairs; seeds 1–1.3 mm, generally in 2 rows ..... B. shockleyi (2)

8' Stem proximally with generally 3–7-rayed hairs; seeds 1.4–6 mm, in 1 row

9. Basal leaves > 6 mm wide; fruit erect to ascending; seeds 2.5–6 mm, wing 0.7–1.8 mm wide ..... B. repanda (2)

9' Basal leaves < 6 mm wide; fruit horizontal to pendent (appressed); seeds 1.4–2.5 mm, wing 0.05–0.3 mm wide

10. Style < 0.2 mm; basal leaves generally dentate; fruit 1.9–2.2 mm wide; seeds 1.4–1.8 mm ..... B. puberula

10' Style 1.5–2 mm; basal leaves entire; fruit 2.5–3 mm wide; seeds 2–2.5 mm ..... B. serpenticola (2)

7' Petals generally > 9 mm

11. At least some basal leaves prominently dentate to ± pinnately lobed; style 0.5–1 mm; ovules < 60 ..... B. subpinnatifida

11' Basal leaves generally entire; style generally < 0.5 mm; ovules > 60

12. Basal leaves 1–2 mm wide; inflorescence 7–15-flowered; fruit pedicel generally ascending near base, recurved near tip ..... B. lincolnensis

12' Basal leaves 3–13 mm wide; inflorescence > 15-flowered; fruit pedicel descending or horizontal near base

13. Fruit generally > 7 cm, sparsely hairy throughout; seeds 1.7–2 mm, generally in 1 row ..... B. californica (2)

13' Fruit generally < 7 cm, hairy on distal 2/3, glabrous near base; seeds 2–2.5 mm, generally irregularly in 2 rows ..... B. xylopoda

1' Fruit, ovary glabrous

14. Cauline leaf base not lobed

15. Style > 2.2 mm

16. Petals ± white, 6–8 mm; fruit pendent, 4–7.5 cm ..... B. constancei

16' Petals lavender to purple, 8–13 mm; fruit ascending, 1.5–2.5 cm ..... B. parishii

15' Style < 2.2 mm

17. Basal leaves glabrous or hairs simple only

18. Leaf margins with minute simple hairs; petals 4–5 mm ..... B. shevockii

18' Leaves glabrous; petals 6–10 mm

19. Caudex with crowded, persistent leaf bases; fruit ascending, not appressed to inflorescence axis; seeds in 1 row ..... B. davidsonii

19' Caudex without crowded, persistent leaf bases; fruit erect, appressed to inflorescence axis; seeds generally in 2 rows ..... B. lyallii (3)

17' Basal leaves with at least some branched hairs

20. Plant generally glabrous throughout except margins of basal leaves

21. Fruit generally > 3 mm wide; seeds 3–6 mm

22. Margins of basal leaves with some 3–4-rayed hairs; ovules 18–30; pollen spheric ..... B. covillei (3)

22' Margins of basal leaves with simple and 2-rayed hairs; ovules 10–20; pollen ellipsoid ..... B. howellii (2)

21' Fruit generally < 3 mm wide; seeds 1.5–2.2 mm

23. Petals 6–8.5 mm; fruit pedicel erect; seeds generally in 2 rows ..... B. lyallii (3)

23' Petals 4–5 mm; fruit pedicel ascending; seeds in 1 row ..... B. tiehmii (2)

20' Plant at least hairy on surfaces of basal leaves, generally throughout pl

24. Fruit pendent or descending

25. Fruit 5–8 mm wide; seeds 5–6 mm ..... B. glaucovalvula

25' Fruit < 3 mm wide; seeds < 2 mm

26. Fruit pedicel base generally abruptly recurved; fruit reflexed, generally appressed to inflorescence axis; cauline leaves 15–40; inflorescence generally > 15-flowered ..... B. retrofracta (3)

26' Fruit pedicel base not abruptly recurved; fruit wide-pendent, not appressed to inflorescence axis; cauline leaves 2–17; inflorescence < 15-flowered

27. Surfaces of basal leaves with simple and 2-rayed hairs ..... B. pendulina (2)

27' Surfaces of basal leaves with 4–8-rayed hairs ..... B. pendulocarpa

24' Fruit erect, ascending, or horizontal

28. Inflorescence 1-sided in fruit ..... B. lemmonii (3)

28' Inflorescence not 1-sided in fruit

29. Basal leaves generally wavy-margined to dentate, generally > 10 mm wide ..... B. repanda (2)

29' Basal leaves entire, generally < 10 mm wide

30. Proximal stems with simple and branched hairs

31. Petals lavender to purple; fruit 1.3–2 mm wide; ovules 24–40 ..... B. paupercula (2)

31' Petals white; fruit 4–5 mm wide; ovules 8–12 ..... B. pygmaea

30' Proximal stems with branched hairs only

32. Surfaces of basal leaves with at least some 8–14-rayed hairs

33. Petals 5–6 mm; style < 0.5 mm ..... B. dispar

33' Petals 9–14 mm; style 0.7–2 mm ..... B. johnstonii

32' Surfaces of basal leaves with 2–7-rayed hairs only

34. Fruit 3–5.5 mm wide; seeds 3–8 mm, wing 0.8–2.5 mm wide

35. Basal leaves with short-stalked hairs generally 0.1–0.25 mm; fruit edges wavy, constricted between seeds ..... B. platysperma

35' Basal leaves with long-stalked hairs generally 0.25–0.5 mm; fruit edge not wavy or constricted between seeds ..... B. ultraalsa

34' Fruit 2–3.2 mm wide; seeds 2.5–3.5 mm, wing 0.2–0.9 mm wide

36. Sepals glabrous; basal leaves 2–6 mm wide, with generally sessile hairs; fruit erect-ascending, generally appressed to inflorescence axis ..... B. elkoensis (2)

36' Sepals sparsely hairy; basal leaves 1–3 mm wide, with stalked hairs; fruit ascending, not appressed to inflorescence axis ..... B. pinzliae (2)

14' Cauline leaf base lobed

37. Stems glabrous proximally

38. Fruit erect, generally appressed to inflorescence axis

39. Basal leaves with sessile 2-rayed mixed with 3- or 4-rayed hairs ..... B. calderi

39' Basal leaves with either sessile 2-rayed or short-stalked 2–6-rayed hairs, or occasionally glabrous

40. Petals white, occasionally pale lavender in age; cauline leaves 6–52; surfaces or margins of basal leaves with sessile 2 rayed hairs, occasionally glabrous ..... B. stricta (2)

40' Petals lavender to purple; cauline leaves 1–7; surfaces of basal leaves glabrous, margins with simple and short-stalked, branched hairs, occasionally glabrous

41. Ovules generally < 30; seed in 1 row, > 3 mm, wing 1–1.5 mm wide ..... B. covillei (3)

41' Ovules generally > 30; seed generally in 2 rows, < 3 mm, wing 0.3–0.5 mm wide ..... B. lyallii (3)

38' Fruit reflexed, pendent, horizontal, or ascending (± erect), generally not appressed to inflorescence axis except generally when reflexed

42. Fruit pendent to strongly reflexed

43. Stems arising at ground level, generally lacking woody bases; surfaces of basal leaves with some simple hairs; inflorescence generally > 12-flowered ..... B. rectissima (2)

43' Stems elevated above ground level on woody base; surfaces of basal leaves lacking simple hairs, generally glabrous; inflorescence generally < 12-flowered

44. Petals 8–11 mm, ± white; fruit 2.5–3.5 mm wide; inflorescence 3–7-flowered ..... B. rollei

44' Petals 4.5–6 mm, ± purple or rose at least near tip; fruit 3–6 mm wide; inflorescence 6–12-flowered ..... B. suffrutescens (3)

42' Fruit ascending to horizontal or ± descending (± erect)

45. Cauline leaves > 14; seeds in 2 rows; fruit 6–10 cm; Channel Islands ..... B. hoffmannii (2)

45' Cauline leaves < 14; seeds in 1 row; fruit generally < 6 cm; montane habitats on mainland

46. Fruit > 2.9 mm wide; seeds 3–6 mm

47. Margins of basal leaves with some 3–4-rayed hairs; ovules 18–30; pollen spheric ..... B. covillei (3)

47' Margins of basal leaves with simple and 2-rayed hairs; ovules 10–20; pollen ellipsoid ..... B. howellii (2)

46' Fruit < 2.9 mm wide; seeds 1–2.2 mm

48. Inflorescence 1-sided in fruit ..... B. lemmonii (3)

48' Inflorescence not 1-sided in fruit

49. Surfaces, margins of basal leaves with 4–7-rayed hairs; ovules 56–80; pollen spheric ..... B. peirsonii (2)

49' Surfaces of basal leaves glabrous, margins with simple and 2–3-rayed hairs; ovules 14–22; pollen ellipsoid ..... B. tiehmii (2)

37' Stems hairy proximally

50. Fruit descending, pendent, or strongly reflexed

51. Fruit pedicel base generally abruptly recurved

52. Fruit > 2.7 mm wide; ovules 20–30; inflorescence 6–12-flowered ..... B. suffrutescens (3)

52' Fruit < 2.7 mm wide; ovules 46–126; inflorescence generally > 12-flowered

53. Stem proximally with branched hairs only ..... B. retrofracta (3)

53' Stem proximally with simple and branched hairs, or simple hairs only

54. Stem proximally with simple and branched hairs; petals 4–6 mm ..... B. pinetorum (3)

54' Stem proximally with simple hairs only; petals 3–4 mm ..... B. rectissima (2)

51' Fruit pedicel base ± recurved or straight

55. Fruit pedicel hairy

56. Stem proximally with simple and branched hairs, or simple hairs only

57. Petals generally > 8 mm, purple to magenta; stems elevated above ground level on woody caudex with crowded, persistent leaf bases; pollen ellipsoid ..... B. koehleri (3)

57' Petals generally < 8 mm, lavender to white; stems from ± ground level, generally lacking woody caudex and crowded, persistent leaf bases; pollen spheric

58. Fruit spreading-descending; fruit pedicel with many 2–3-rayed hairs ..... B. pauciflora (2)

58' Fruit reflexed to ± appressed; fruit pedicel with few simple and 2-rayed hairs only, occasionally glabrous ..... B. pinetorum (3)

56' Stem proximally with branched hairs only

59. Petals generally > 9 mm; fruit generally > 6 cm ..... B. californica (2)

59' Petals generally < 9 mm; fruit generally < 6 cm

60. Surfaces of basal leaves with hairs 0.1–0.2 mm; seed wing 0.25–0.5 mm wide; ovules 34–64; pollen ellipsoid ..... B. cobrensis (2)

60' Surfaces of basal leaves with hairs 0.2–0.7 mm; seed wing < 0.25 mm wide; ovules 74–134; pollen spheric ..... B. inyoensis (2)

55' Fruit pedicel glabrous (sparsely hairy)

61. Petals generally > 8 mm, purple to magenta; caudex woody, leaf bases crowded, persistent ..... B. koehleri (3)

61' Petals generally < 8 mm, white to lavender (rose-purple); caudex woody or not, crowded-persistent leaf bases 0

62. Fruit > 2.7 mm wide; seed wing > 0.7 mm wide; stems elevated above ground surface on woody caudex ..... B. suffrutescens (3)

62' Fruit < 2.7 mm wide; seed wing < 0.7 mm wide; stems generally not elevated above ground surface on woody caudex

63. Fruit reflexed to ± appressed; pollen spheric; Klamath Ranges, Cascade Range, Sierra Nevada

64. Stem proximally with stalked, 2–5-rayed hairs; seeds 1.5–1.8 mm ..... B. pinetorum (3)

64' Stem proximally with ± sessile, 2-rayed hairs; seeds 2–2.5 mm ..... B. tularensis

63' Fruit wide-pendent to spreading-descending, not appressed; pollen ellipsoid; Southwestern California, Great Basin Floristic Province, D

65. Stem proximally generally simple-hairy; seeds in 2 rows ..... B. pendulina (2)

65' Stem proximally generally branched-hairy; seeds in 1 row

66. Basal leaves dentate; stem proximally with 2–5-rayed hairs ..... B. perennans

66' Basal leaves entire; stem proximally with 4–10-rayed hairs ..... B. cobrensis (2)

50' Fruit erect, ascending, or horizontal (pendent)

67. Leaf hairs ± sessile, branches generally appressed; sepals generally glabrous

68. Basal leaves with branched hairs 2-rayed only; petals white, occasionally pale lavender in age; pollen ellipsoid ..... B. stricta (2)

68' Basal leaves with some 3–4-rayed hairs; petals purple to lavender (± white); pollen spheric

69. Fruit erect to ascending, generally appressed to inflorescence axis

70. Cauline leaves 3–6; seeds 2.5–3.5 mm ..... B. elkoensis (2)

70' Cauline leaves > 6; seeds 1.4–2 mm ..... B. pratincola

69' Fruit spreading-ascending to horizontal, not appressed to axis

71. Cauline leaves generally > 10; fruit 1.7–2.5 mm wide; seeds 1.4–2 mm ..... B. divaricarpa

71' Cauline leaves generally < 10; fruit 2.5–3.5 mm wide; seeds 2.5–3.2 mm ..... B. rigidissima

67' Leaf hairs stalked, branches not appressed; sepals generally hairy

72. Stem proximally with some simple hairs

73. Fruit erect, appressed to inflorescence axis; ovules 24–40 ..... B. paupercula (2)

73' Fruit ascending to horizontal, not appressed to inflorescence axis; ovules > 40

74. Fruit pedicel hairs 2–4-rayed only

75. Fruit 1.2–1.5 mm wide, ovules 46–52; leaf surface hairs < 0.3 mm ..... B. evadens

75' Fruit 1.5–2.2 mm wide, ovules 80–250; leaf surface hairs >= 0.3 mm

76. Petals 9–14 mm, purple; fruit pedicel generally > 10 mm; pollen ellipsoid ..... B. arcuata (2)

76' Petals 5–8 mm, lavender to ± white; fruit pedicel generally < 10 mm; pollen spheric ..... B. pauciflora (2)

74' Fruit pedicel glabrous or with simple, occasionally some 2-rayed hairs

77. Basal leaves generally <= 3 mm wide; caudex woody, with crowded, persistent leaf bases ..... B. koehleri (3)

77' Basal leaves generally > 3 mm wide; caudex woody or not, crowded-persistent leaf bases 0

78. Distal cauline leaves glabrous, occasionally ciliate; cauline leaf basal lobes generally > 3 mm; Northwestern California, Cascade Range, East of Sierra Nevada ..... B. sparsiflora

78' Distal cauline leaves hairy; cauline leaf basal lobes generally < 3 mm; widespread

79. Stem proximally with some 3 rayed, 0.1–0.5 mm hairs ..... B. rubicundula

79' Stem proximally with simple and 2-rayed hairs only (all simple), 0.4–1 mm ..... B. breweri

80. Stem 0.6–2 dm; fruit pedicel generally < 9 mm, hairy ..... subsp. breweri (2)

80' Stem 1.8–4.5 dm; fruit pedicel generally > 9 mm, glabrous or hairs few, scattered ..... subsp. shastaensis

72' Stem proximally with branched hairs only

81. Inflorescence 1-sided in fruit ..... B. lemmonii (3)

81' Inflorescence not 1-sided in fruit

82. Stem proximally with at least some 2–3-rayed hairs

83. Petals 8–10 mm; inflorescence 30–70-flowered; pollen ellipsoid; Channel Islands ..... B. hoffmannii (2)

83' Petals 4–7 mm; inflorescence 5–25-flowered; pollen spheric; mainland montane areas

84. Petals white or lavender; fruit < 1.9 mm wide; Klamath Ranges ..... B. acutina

84' Petals purple; fruit > 1.9 mm wide; San Bernardino Mountains, White and Inyo Mountains

85. Inflorescence 12–25-flowered; stem proximally with hairs 0.4–0.6 mm only; seeds 1–1.5 mm; San Bernardino Mountains ..... B. peirsonii (2)

85' Inflorescence 5–8-flowered; stem proximally with hairs 0.05–0.2 mm only; seeds 2.5–3.5 mm; White and Inyo Mountains ..... B. pinzliae (2)

82' Stem proximally with 4–12-rayed hairs only

86. Petals 3–5 mm

87. Stems > 1.5 dm; fruit 4–6.2 cm; ovules 48–68 ..... B. bodiensis

87' Stems generally < 1.5 dm; fruit 1.7–4.5 cm; ovules 32–44 ..... B. depauperata

86' Petals 5–9 mm

88. Style 1.5–2 mm; ovules 20–24 ..... B. serpenticola (2)

88' Style < 0.7 mm; ovules 74–190

89. Petals 1.2–2 mm wide; surfaces of basal leaves with hairs 0.2–0.7 mm; seeds 1.7–2 mm; pollen spheric ..... B. inyoensis (2)

89' Petals 0.8–1.2 mm wide; surfaces of basal leaves with hairs 0.1–0.2 mm; seeds 1–1.3 mm; pollen ellipsoid ..... B. shockleyi (2)

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