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Eschscholtz's hairy rock-cress, Eschscholtz's rockcress, hairy rockcress, Pacific coast rockcress

Habit Biennials or perennials; (caudex branched); usually densely hirsute (at least basally), trichomes simple or stalked, forked, sometimes glabrescent with mostly simple ones.
Stems

simple or several from base (rosette), erect, often branched distally, 2–7(–10) dm, (hirsute basally, trichomes simple and minutely stalked, forked, rarely almost exclusively glabrous).

Basal leaves

petiole 0.7–3 cm, (ciliate or not);

blade broadly spatulate to narrowly oblanceolate, 1.2–10 cm × 7–30 mm, margins entire or dentate, apex obtuse or acute, surfaces usually pubescent, sometimes glabrous, trichomes simple, forked and stalked, stellate.

Cauline leaves

(2–)4–12(–18), (well-spaced or, rarely, overlapping);

blade ovate to oblong or lanceolate, 1.5–6.5(–10) cm × 5–30 mm, base auriculate, margins dentate or entire, apex acute or obtuse, surfaces sparsely hirsute or glabrous.

Racemes

simple or branched.

Flowers

sepals oblong, 3.5–5 × 1.2–2 mm, lateral pair saccate basally;

petals white, rarely pink, linear-oblanceolate or narrowly spatulate, (5.5–) 6.5–9(–10) × 1.5–3 mm, apex obtuse;

filaments 3.5–6 mm;

anthers oblong, 0.7–1 mm.

Fruiting pedicels

erect to erect-ascending, 3.5–10(–15) mm, (glabrous or sparsely pubescent).

Fruits

erect to erect-ascending, (often appressed to rachis), torulose, 3.5–6.5 cm × 1.2–1.8(–2) mm;

valves each with prominent midvein extending full length or to middle;

ovules 54–80 per ovary;

style (0.1–)0.3–1 mm.

Seeds

usually narrowly winged throughout or only distally, rarely not winged, oblong or suborbicular, 1–1.8 × 0.9–1.3 mm;

wing to 0.2 mm wide distally.

2n

= 32, 64.

Arabis eschscholtziana

Phenology Flowering (Apr-)May–Jul.
Habitat Rocky slopes, crevices, and ledges, meadows, moist banks and grounds, granitic soil, wooded slopes
Elevation 0-2800 m (0-9200 ft)
Distribution
from FNA
AK; CA; ID; MT; NV; OR; UT; WA; WY; AB; BC; YT
[WildflowerSearch map]
[BONAP county map]
Discussion

G. A. Mulligan (1996) recognized Arabis eschscholtziana as a distinct species; R. C. Rollins (1941, 1993) treated it as a variety of A. hirsuta. As discussed under A. pycnocarpa, A. hirsuta does not occur in North America, and the characters separating all three species (see key to species), as well as the different ploidy levels, support Mulligan’s conclusion.

Both M. Hopkins (1937) and R. C. Rollins (1941, 1993) recognized the glabrous or subglabrate forms native to North America as a distinct variety, var. glabrata; G. A. Mulligan (1996) did not accord such forms any taxonomic status. Glabrous and subglabrate forms occur in both Arabis eschscholtziana and A. pycnocarpa and sometimes even within a population that has moderately to densely pubescent forms. I support Mulligan’s view in not recognizing the glabrous forms as an infraspecific taxon.

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

Source FNA vol. 7, p. 261.
Parent taxa Brassicaceae > tribe Arabideae > Arabis
Sibling taxa
A. aculeolata, A. alpina, A. blepharophylla, A. caucasica, A. crucisetosa, A. furcata, A. georgiana, A. mcdonaldiana, A. modesta, A. nuttallii, A. olympica, A. oregana, A. patens, A. pycnocarpa
Synonyms A. hirsuta subsp. eschscholtziana, A. hirsuta var. eschscholtziana, A. hirsuta var. glabrata, A. ovata var. glabrata, A. pycnocarpa var. glabrata, A. rupestris, A. stelleri var. eschscholtziana, Turritis spathulata
Name authority Andrzejowski: in C. F. von Ledebour, Fl. Altaica 3: 25. (1831)
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