Isatis tinctoria, dyer's woad

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Intermountain Flora
Winter annual, biennial, or short-lived perrenial, from a taproot; herbage glaucous, glabrous, or hirsute at the base with simple hairs; stem erect, usually single, brached above; leaves basal and cauline, the basal rosulate, petiolate, oblanceolate to elliptic-oblanceolate, up to 18 cm long (measurement including the petiole), entire to weakly dentate, the cauline leaves lanceolate, sessile and auriculate, entire, becoming progressively smaller upwards; racemes numerous, forming a panicle, dense in flower and elongating in fruit; sepals 1.3-2.1 mm long, oblong, rounded, glabrous; petals 2.4-3.4 mm long, 3-5 mm wide, oblanceolate, rounded apically, not clawed, yellow; fruiting pedicels 6-10 mm long, slender for ¾ their length, expanded at the apex, recurved; silicles 12-18 (22) mm long, oblanceolate, gradually tapering from near the apex to the base where rounded, rounded-emarginate to truncate-emarginate apically, strongly flattened at a right angle to the plane of the septum, obscurely differentiated into 2 halves, lacking a septum and containing only 1 seed positioned where the septum would be, becoming dark purplish-brown with maturity, indehiscent; stigma sessile; seed 2.7-3.5 mm long, narrowly oblong to narrowly oboviod, orange, the cotyledons incumbent; 2n = 14, 16, 18, 28, 36.

Cronquist, A., Holmgren, N.H., and Holmgren, P.K. (2005) "Intermountain Flora" pg. 272, vol. 2 part B, The New York Botanical Garden New York.