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Noxious Weeds


Dyer’s woad/Marlahan mustard (Isatis tinctoria L)

Mustard family (Brassicaceae) 

Photo of Dyer's woad

 

GROWTH HABIT:
Dyer’s Woad, a European native, is a winter annual, biennial or short-lived perennial. The mature plant is 12 to 39 inches (30 to 100 cm) tall with erect branches from the base. The lower lateral branches may lie close to ground but rise at the end (decumbent). Dyer’s woad produces a long, thick tap root which can reproduce a new plant if the first is cut off. . Dyer’s woad begins flowering in April and matures in June or early July in northern Nevada.
LEAVES: 
The leaves are bluish green, whitened with a bloom (glaucous), are borne alternately on the stems, and mostly without hairs, except for some fine hairs (cilia) on the midrib of the lower leaves. The lower leaves are oblong and lance shaped with coarsely toothed blades that are 2 to 4 inches (5 to 10 cm) long; these narrow to a stalk nearly as long as the leaf blade. The upper leaves are smaller, narrower, and stalkless, and clasp the stem with earlike projections (auricles).
FLOWERS:
The yellow flowers are tiny, 1/8 inch (3 mm) long, and are crowded into flat-topped or convex, simple, elongated clusters (corymbose). The outer flower stalks are longer than the inner ones.
SEEDS:
A single seed is produced in a purplish-brown, narrow, 1/2 inch (12 mm) long pod. The yellowish seeds 1/8 to 1/7 inch (3 to 3.5 mm) long. Seeds mature in late spring and early summer. The seed leaves (cotyledons) are light green and oval shaped, and are 1/2 to 1/4 times as long as they are broad with short stalks 1/8 to 1/4 inch (3 to 6 mm) long. The first true leaf is broad at the top and tapers gradually to a short stalk (spatulate). It has a somewhat prominent midvein and is smooth around the margin (entire).
OTHER:
Dyer’s Woad infests wildlands, grain fields, pastures, waste areas, and grows along roadsides and fencerows. It may be a problem in cultivated row crops and orchards.
KEY CHARACTERS:
The yellow flowers are tiny, 1/8 inch (3 mm) long, and are crowded into flat-topped or convex, simple, elongated clusters (corymbose).
DISTRIBUTION:Throughout agricultural areas in Inyo/Mono Counties