This section is from the book "A Manual Of Weeds", by Ada E. Georgia. Also available from Amazon: A Manual Of Weeds.
Introduced. Annual or biennial. Propagates by seeds.
Time of bloom: June to September.
Seed-time: July to October.
Range: Ontario, Manitoba, and British Columbia, Minnesota and the Dakotas.
Habitat: Grain fields and waste places.
Stem one to two feet tall, slender, usually simple to the flowering stalk, finely roughened with forking hairs. Basal leaves oblong to lance-shaped, tapering to a slim petiole; those on the stem arrow-shaped, long-pointed, clasping the stem with auricled base; all clothed with fine, branching hairs. Flowers in a terminal panicle, containing several slender racemes tipped with small clusters of orange-colored blossoms, not more than an eighth of an inch across; maturing,
Fig. 126. -Ball
Mustard (Neslia paniculata). X 1/2 the flowers leave behind a string of bead-like silicles of lesser diameter; as they ripen the tiny balls become netted and pitted, growing smaller yet, until it would take a dozen to measure an inch. Each ball contains one small, yellow seed, which does not "shell" but drops from the plant, pod and all, looking like a speck of dry, brown earth; the seeds are a common impurity of poorly cleaned grain and are overlooked and mistaken for harmless dirt in seed wheat and oats. (Fig. 126.) Means of control the same as for Field Peppergrass.