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alpine rockcress, arabis alpina

spreading rockcress

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. Biennials or, rarely, perennials; (short-lived, with caudex); usually densely hirsute (at least basally), trichomes simple (to 1 mm), sometimes mixed with stalked, forked ones.
Stems

usually simple from base, erect to ascending, often branched proximally, (0.6–)1–2(–2.5) dm.

simple or several from base (rosette), erect, often branched distally, (1.8–)2.5–4.5(–5.5) dm, (hirsute at least basally).

Basal leaves

petiole 0–1 cm;

blade spatulate, oblanceolate, oblong, or obovate, (0.4–)1–4(–5) cm × (3–)6–15(–20) mm, margins dentate to denticulate, apex obtuse or acute, surfaces usually pubescent, rarely subglabrate, trichomes stellate with simple rays.

petiole (0.7–)2–5 cm;

blade usually ovate to oblanceolate, rarely cordate, (0.8–)1.5–3 cm × 5–17 mm, margins dentate or serrate, surfaces sparsely to densely pubescent, trichomes simple or forked.

Cauline leaves

3–5(–6);

blade oblong or ovate, 1–3 cm × 5–15 mm, base subcordate or auriculate, margins usually dentate, rarely subentire, apex acute or obtuse.

(5–)8–20(–27), (overlapping or not);

blade ovate to oblong or lanceolate, (2–)3–7.5(–9) cm × (10–)13–25(–35) mm, base amplexicaul, margins usually dentate or serrate, sometimes entire, surfaces hirsute.

Racemes

simple, (lax).

branched.

Flowers

sepals oblong, 2.5–4(–4.7) × 1–2 mm, lateral pair conspicuously saccate basally;

petals white, spatulate to obovate, 5–8(–9) × 2–3.5 mm, apex obtuse;

filaments 3–5 mm;

anthers oblong, 0.7–1.2 mm.

sepals oblong, 2.5–4.5 × 1–1.5 mm, lateral pair slightly saccate basally;

petals white, spatulate, (5–)6–9 × 2–3.5 mm, apex obtuse;

filaments 3–5 mm;

anthers oblong, 0.8–1.2 mm.

Fruiting pedicels

ascending to divaricate, 4–10(–12) mm.

ascending to divaricate-ascending, (7–)10–20(–24) mm, (glabrous or sparsely pubescent).

Fruits

ascending to spreading, torulose, 1.7–3.5(–4) cm × 1–1.7 mm;

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

ovules 34–50 per ovary;

style 0.3–0.6 mm.

divaricate to erect-ascending, (not appressed to rachis), torulose, 2.2–4.6 cm × 0.8–1.2mm;

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

ovules 16–28 per ovary;

style 0.5–2 mm, (slender).

Seeds

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

wing 0.1–0.2 mm wide.

narrowly winged distally, oblong, 1–1.6 × 0.6–0.8 mm;

wing 0.05–0.1 mm.

2n

= 16.

Arabis alpina

Arabis patens

Phenology Flowering Jun–Aug. Flowering Apr–May.
Habitat Crevices of limestone rocks, along streams, calcareous alpine meadows, Salix scrub on slopes with scree Rocky wooded slopes, shady stream banks, limestone ledges and bluffs
Elevation 0-2400 m (0-7900 ft) 0-500 m (0-1600 ft)
Distribution
from FNA
NY; WA; NL; NU; QC; Greenland; Europe; sw Asia; n Africa; tropical Africa
[WildflowerSearch map]
[BONAP county map]
from FNA
DC; IN; KY; MD; NC; OH; PA; TN; VA; WV
[WildflowerSearch map]
[BONAP county map]
Discussion

Arabis alpina, the generic type, is variable. It is cultivated extensively for its attractive flowers, and it sometimes escapes from cultivation. There is disagreement as to whether one or more species should be recognized in this complex. European, some African, and most North American plants are recognized as A. alpina; most of the larger-flowered, southwestern Asian plants, which are most commonly cultivated, are recognized as A. caucasica or as A. alpina subsp. caucasica (Willdenow) Briquet. In my opinion, the morphological differences between the two (see key, couplet 3) support recognition of two species, as did R. C. Rollins (1993) and G. A. Mulligan (1996).

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

Source FNA vol. 7, p. 259. FNA vol. 7, p. 262.
Parent taxa Brassicaceae > tribe Arabideae > Arabis Brassicaceae > tribe Arabideae > Arabis
Sibling taxa
A. aculeolata, A. blepharophylla, A. caucasica, 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. oregana, A. pycnocarpa
Synonyms A. alpina var. glabrata Boechera patens
Name authority Linnaeus: Sp. Pl. 2: 664. (1753) Sullivant: Amer. J. Sci. Arts 42: 49. (1842)
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