Hairy Rockcress

Foodplant / feeds on
larva of Ceutorhynchus unguicularis feeds on Arabis hirsuta

Foodplant / parasite
Erysiphe cruciferarum parasitises live Arabis hirsuta

Foodplant / spot causer
colony of Pseudocercosporella anamorph of Mycosphaerella capsellae causes spots on live leaf of Arabis hirsuta

A highly variable species, especially in spacing, shape, texture, base, and margin of cauline leaves, flower color, petal size, and density of indumentum. Many of the variants have been recognized at specific and infraspecific ranks. However, since the variation in China does not follow consistent morphological and/or geographical patterns, it is better to recognize only one variable taxon.

The records in FRPS and Fl. Xinjiang. (2(2): 142. 1995) of Arabis borealis Andrzejowski from Xinjiang, as well as those in FRPS and Fl. Guizhou. (7: 30. 1989) of A. sagittata de Candolle from Guizhou, are based on misidentified plants of A. hirsuta. Typical plants of A. sagittata are diploid (2n = 16) biennials with strongly sagittate cauline leaves, whereas those of A. hirsuta are tetraploid perennials or occasionally biennials with auriculate or subcordate cauline leaves. However, the distinction between the two is often difficult, especially in biennial plants of A. hirsuta. The present authors have examined no Chinese material that belongs to either A. borealis or A. sagittata.

Herbs perennial or sometimes biennial, (4-)10-80(-110) cm tall, usually densely hispid, with simple and stalked, forked or substellate trichomes. Stems erect, usually simple basally, often branched above. Basal leaves rosulate; petiole (0.5-)1-2 cm; leaf blade spatulate, oblanceolate, or oblong, (1.5-)2.5-8(-10) × (0.5-)1-2.5 cm, pubescent, margin entire, repand, or dentate, apex obtuse or acute. Cauline leaves sessile, lanceolate, oblong, oblanceolate, or ovate, (1-)1.5-5(-7) × (0.5-)1-2 cm, hirsute on both surfaces or adaxially glabrescent, base subcordate or auriculate and with obtuse or subacute auricles, margin dentate or entire, apex acute or obtuse. Racemes ebracteate. Fruiting pedicels erect to erect-ascending, (2-)3-10(-15) mm, slender, glabrous or sparsely hirsute. Sepals narrowly oblong, 2.5-4 × 0.5-1.2 mm, not saccate. Petals white, rarely pink or purplish, linear-oblanceolate or narrowly spatulate, rarely linear, (3.5-)4-5 × 1-1.5 mm, apex obtuse. Filaments slender, 2.5-4.5 mm; anthers oblong, 0.7-1 mm. Ovules 30-80 per ovary. Fruit linear, (1.5-)2-5.5(-7) cm × 0.8-1.2 mm, erect to erect-ascending, often subappressed to rachis, flattened; valves glabrous, torulose, with a prominent midvein extending full length; style (0.1-)0.3-0.8(-1) mm. Seeds brown, oblong or suborbicular, (0.8-)1-1.5(-1.7) × 0.8-1.3 mm, uniseriate, wingless, narrowly winged all around, or winged distally. Fl. Apr-Aug, fr. May-Sep. 2n = 32.

Anhui, Gansu, Guizhou, Hebei, Heilongjiang, Henan, Hubei, Jilin, Liaoning, Nei Mongol, Ningxia, Qinghai, Shaanxi, Shandong, Shanxi, Sichuan, Xinjiang, Xizang, Yunnan, Zhejiang [Japan, Kazakhstan, Korea, Russia; N Africa, SW Asia, Europe, North America].

Meadows, grassy slopes, roadsides, mixed forests; 300-4000 m.

Turritis hirsuta Linnaeus, Sp. Pl. 2: 666. 1753; Arabis hirsuta var. nipponica (Franchet & Savatier) C. C. Yuan & T. Y. Cheo; A. hirsuta var. purpurea Y. C. Lan & T. Y. Cheo; A. sagittata de Candolle var. nipponica Franchet & Savatier.

15-60 cm

Arabis hirsuta, known as hairy rock-cress, is a flowering plant of the genus Arabis in the family Brassicaceae. In previous North American works, this species has been broadly defined to include plants native to Europe, Asia, and the northern half of North America, but is now more often restricted to a narrower subgroup restricted to Europe.

This erect, 15–60 cm (6-18 inches) high hairy plant is usually unbranched, with a long spike of flowers. Lower leaves form a rosette, the stalkless upper-leaves clasp the stem. The white petals are twice as long as the sepals, flowers June–August. The fruits are cylindrical and pressed close to the stem and the slightly winged seeds are reddish brown. The hairs are stiff and forking. The species grows on chalk slopes, dunes, hedgebanks, walls and rocks.

Conservation status in the UK is near threatened as of 2001.