TUMBLE MUSTARD, Sisymbrium altissimum L. 1, lower leaf; 2, root; 3, upper part of plant; 4, seed; 5, seed pod. Annual or winter annual, reproducing by seed, taprooted. Stem erect, 2 to 5 feet (0.6 to 1.5 m) tall, bushy, branching. Stem and branches smooth above, somewhat hairy below, pithy. Leaves pale green. Lower leaves are large and divided; upper leaves have smaller narrow segments. Flowers yellowish-white, 1/4 to 1/2 inch (6 to 13 mm) in diameter, 4-petaled, growing in numerous but short racemes. Seed pods stiff, narrow, 2 to 4 inches (5 to 10 cm) long, divided into 2 parts; look like long stems rather than seed pods. Seeds oblong, about 1/16 inch (1.5 mm) long, dark reddish-brown. Found in small grains and waste places. Stem often breaks off at maturity causing the plant to be blown about by wind.