Mustards (Brassica spp.)
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Mustards are winter or summer annual broadleaf plants, and sometimes biennials. Mustard species vary greatly and there are regional biotypes for most species. Cultivars of some mustards have been developed for oil, seasoning, and fodder. However, cultivars that escape hybridize readily with wild types. Wild mustards (and cultivated ones) can harbor pests and diseases that damage closely related crops. Roots, leaves, and especially seeds of Brassica and related species have sulfur-containing compounds. When consumed in large quantities over time, these compounds can irritate the digestive tracts and cause thyroid problems in livestock. Mustards may become a fire hazard when they dry up at the end of their growing season.
All mustard seedlings have broad cotyledons (seed leaves) that are more or less kidney shaped, broader than long, hairless, and have a deep notch at the tip. Their stalks are longer than the cotyledon blade. The first true leaves are bright green on the upper surface and paler below.
Stems are branched and their upper portions are usually hairless. Leaves are toothed, and are alternate to one another along the stem. Basal leaves are somewhat lobed and the lobe at the tip is round to somewhat round. Upper stem leaves are reduced and stalkless.
Mature mustards have dense clusters of four-petaled, yellow flowers at the tips of branches.
The Fruits are pods 1/2 to 3/4 of an inch (13–19 mm) long and approximately 1/12 inch (3.7 cm) broad. They are tipped with short slender beaks and stand close to the stem, often overlapping one another.
Seeds are small, ranging from roughly 2/5 to 1/10 of an inch (1 to 3 mm) in diameter, and are nearly round to elliptical to egg shaped, depending on the species.
Reproduces by seed.