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garden rockcress, mountain rockcress, rock cress

Oregon rock-cress

Habit Perennials; (stoloniferous, with vegetative rosettes, loosely cespitose to somewhat pulvinate); sparsely to moderately pubescent, trichomes stalked, cruciform, stellate, mixed with simple and forked-stalked ones. Perennials; (caudex simple or branched, with some persistent petiolar remains); sparsely to moderately pubescent, trichomes bulbous-based, simple and long-stalked, forked, (to 2 mm), these often mixed with fewer 3-rayed, stalked stellate ones.
Stems

several to many from base, erect, ascending to decumbent, branched (several), 1.5–3.5(–5) dm.

simple or few from base (caudex), erect, unbranched distally, (0.6–)1.7–4.5(–5) dm, (usually pubescent throughout, rarely subglabrate, coarsely hirsute, trichomes simple, mixed with forked ones).

Basal leaves

petiole 0–1 cm;

blade spatulate, oblanceolate, oblong, or obovate, 2–5.5(–8) cm × 9–18(–25) mm, margins dentate to denticulate, apex obtuse or acute, surfaces usually pubescent, rarely subglabrate, trichomes stellate with some rays branched.

petiole 0.5–2(–3) cm, (ciliate);

blade oblanceolate to obovate, (1–)2–5(–9) cm × (5–)8–18(–22) mm, margins entire or repand to dentate, (ciliate), apex obtuse, surfaces pubescent or glabrous, trichomes simple and forked, sometimes mixed with 3-rayed stellate ones.

Cauline leaves

4–8;

blade oblong or ovate, 1–5 cm × 5–20 mm, base subcordate or auriculate, margins usually dentate, rarely subentire, apex acute or obtuse.

3–6 (or 7);

blade oblong, 1–3(–6) cm × 2–7(–15) mm, base not auriculate, margins entire or dentate, (ciliate or not), apex obtuse, surfaces pubescent as basal leaves or glabrous.

Racemes

simple, (lax).

simple, (dense).

Flowers

sepals oblong, 4.5–8 × 1–2 mm, lateral pair conspicuously saccate basally;

petals white, spatulate to obovate, 10–19 × 4–8 mm, apex obtuse;

filaments 4–7 mm;

anthers oblong, 0.7–1.2 mm.

sepals (purple), oblong, (5–)6–8 × 1.5–2 mm, lateral pair saccate basally;

petals purple or pink, spatulate, (10–)12–15(–16) × (3–)4–5 mm, apex obtuse;

filaments (4–)5–8 mm;

anthers narrowly oblong, 1.2–1.8 mm.

Fruiting pedicels

ascending to divaricate, 7–17(–20) mm.

ascending to erect, 5–10 mm, (pubescent or glabrous).

Fruits

ascending to spreading, torulose, (3–)4–7 cm × 1–2 mm;

valves each with midvein absent or obscure, along proximal 1/2;

ovules 40–60 per ovary;

style 0.5–1 mm.

erect or nearly so, slightly torulose, (3–)4.5–6 cm × 1.5–2 mm;

valves each with prominent midvein;

ovules 24–30 per ovary;

style 0.5–1 mm.

Seeds

narrowly winged throughout, ovate, 1–1.4 × 0.9–1.1 mm;

wing 0.1–0.2 mm wide.

narrowly winged distally or not winged, oblong, 1.8–2.2 × ca. 1 mm;

wing ca. 0.1 mm wide.

2n

= 16.

= 32.

Arabis caucasica

Arabis oregana

Phenology Flowering Jun–Aug. Flowering Apr–May.
Habitat Rare garden escape Moist granitic soil, rocky hillsides, chaparrals, steep banks
Elevation 500-1000(-1400) m (1600-3300(-4600) ft)
Distribution
from FNA
MI; NY; BC; NB; ON; QC; YT; sw Asia [Introduced in North America]
[BONAP county map]
from FNA
CA; OR
[WildflowerSearch map]
[BONAP county map]
Discussion

Arabis oregana is known from Napa and Siskiyou counties (California) and Jackson County (Oregon).

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

Source FNA vol. 7, p. 259. FNA vol. 7, p. 264.
Parent taxa Brassicaceae > tribe Arabideae > Arabis Brassicaceae > tribe Arabideae > Arabis
Sibling taxa
A. aculeolata, A. alpina, A. blepharophylla, A. crucisetosa, A. eschscholtziana, A. furcata, A. georgiana, A. mcdonaldiana, A. modesta, A. nuttallii, A. olympica, A. oregana, A. patens, A. pycnocarpa
A. aculeolata, A. alpina, A. blepharophylla, A. caucasica, A. crucisetosa, A. eschscholtziana, A. furcata, A. georgiana, A. mcdonaldiana, A. modesta, A. nuttallii, A. olympica, A. patens, A. pycnocarpa
Synonyms A. purpurascens, A. furcata var. purpurascens
Name authority Willdenow: Enum. Pl., suppl., 45. (1814) Rollins: Rhodora 43: 349. (1941)
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