Isatis tinctoria L.

Isatis species are annual, biennial or perennial herbs, glabrous or pubescent with simple trichomes, not scapose. Rootstocks slender, taproot. Stem erect, ascending, leafy, usually simple at the base, and paniculately branched above, glaucous or rarely pubescent. Basal leaves simple, rosulate or not, linear lanceolate to oblong, base cuneate to attenuate, margin entire to dentate, apex acute to obtuse, petiole short to sessile, cauline leaves usually similar but smaller, base auriculate amplexicaul or sagittate, petiole sessile. Inflorescence raceme corymbs or panicles, many flowered, considerably elongated in fruit, ebracteate. Flowers bisexual, yellow, pedicel erect, filiform, thickened, clavate at the apex, sepals 4, ovate-oblong, erect, lateral pair base not saccate, apex obtuse, petals 4, obovate-oblong, almost equal or slightly longer than sepals, base cuneate, margins entire, apex obtuse or emarginated, claw absent, nectar glands 6 confluent or 4 lateral and median. Stamens 6, slightly tetradynamous, filaments not dilated near the base, anthers ovate-oblong, nectar glands 4 to 6, median glands usually present. Ovary superior, bicarpellary, ovules 1 or 2. Fruit siliqula or samaroid, indehiscent, ovate-elliptic, obovate to suborbicular, terete, angustiseptate, compressed, keeled or shortly winged, distinctly winged, valves prominent or obscurely, glabrous or pubescent, replum and veins united, gynophore, septum absent, style absent, stigma capitate. Seeds 1-2, pendulous, brown, plump, ovate-ovoid, not winged, smooth minutely reticulate, not mucilaginous when soaked, cotyledons usually incumbent.

Isatis species flowers are complete, bisexual, i.e., with functional male (androecium) and female (gynoecium), including stamens, carpels and ovary. Pollination is entomophilous i.e., by insects, or cleistogamy i.e., by self or allogamy i.e., by cross pollination. Flowering/Fruiting: May—July.

Seeds may be dispersed by autochory i.e., self dispersal, anemochory i.e., wind dispersal, zoochory i.e., dispersal by birds or animals, anthropochory i.e., dispersal by humans.

Biennial or rarely perennial herbs, glabrous, about 40-150 cm long, not scapose. Rootstocks slender, taproot. Stem erect, ascending, and simple at the base, branched paniculately above, glaucous, glabrous and rarely pubescent. Basal radical leaves simple, in rosulate, withered early before flowering, oblong-oblanceolate to lanceolate, about 5-15 x 1-3 cm across, base attenuate, margin entire to slightly shallow dentate, apex acute to obtuse, petiole about 0.5-5 cm long, cauline leaves linear and gradually smaller, linear lanceolate, about 3-7 x 0.5-2.5 cm across, base acutely auriculate or amplexicaul, margin entire, apex acute, petiole sessile. Inflorescence raceme panicles, many flowered, considerably elongated in fruit, ebracteate. Flowers bisexual, yellow, pedicel erect, slender, filiform, more or less deflexed, thickened and subclavate at the apex, 5-8 mm long, sepals 4, oblong, erect, lateral pair base not saccate, apex obtuse, glabrous, about about 2-2.5 x 1-1.5 mm across, petals 4, oblanceolate-obovate, almost equal or slightly longer than sepals, base attenuate, margins entire, apex obtuse, about 3-4 x 1-1.5 mm across, claw absent, nectar glands 6 confluent or 4 lateral and median. Stamens 6, slightly tetradynamous, filaments about 1-2 mm long, anthers ovate-oblong, about 0.6 mm long. Ovary superior, bicarpellary, ovules 1 or 2. Fruit siliqula or samaroid, indehiscent, oblong-elliptic, about 10-20 x 3-5 mm across, terete, angustiseptate, compressed, base cuneate, apex rounded to rarely emarginate, distinctly winged, valves prominent or obscurely, glabrous or pubescent, replum and veins united, midvein distinct and lateral veins inconspicuous, gynophore, septum absent, style absent, stigma capitate. Seeds 1, rarely 2, pendulous, yellowish light brown, plump, narrow oblong-ellipsoid, about 2-3 x 0.7-1 mm across, not winged, not mucilaginous when soaked, cotyledons usually incumbent.

Isatis species are susceptible to various insect pests, virus, mildews and moulds.

Roadsides, near cultivated fields and mountain slopes, altitude 700-2700 m.

Not evaluated (IUCN).

Used as medicine as antibacterial, antiviral, astringent, also used as dye and preservative.