An Illustrated Guide to ARIZONA WEEDS

The University of Arizona Press




LONDON ROCKET-Sisymbrium irio L.

DESCRIPTION-A bright green fleshy annual or winter annual, hairless or with a few hairs near the base. The stems are usually much branched from the base 1 to 3 feet high, from a coarse taproot, and reproducing by seeds only. The dark green divided leaves are 1 to 8 inches long including the stalk, with a large pointed terminal lobe, and 1 to 4 pairs of smaller lobes below. The divisions of the upper leaves are almost as large as those on the lower.

The small yellow flowers, 1/12 to 1/8 inch long, are borne on slender stalks in small clusters at the stem tips. The flower stems elongate as the seedpods mature, so there are many, spreading, very narrow pods below the flower clusters. The mature seedpods are 1 1/2 to 2 inches long. The tiny reddish brown oblong seeds are 1/16 inch long, with a ridge and two depressions on each face.

DISTRIBUTION-London rocket is a native European weed. It is abundant throughout the irrigated lands of Arizona, in alfalfa, small grains, gardens, citrus orchards, pastures, roadsides, and waste places; 100 to 4,500 feet elevations; flowering December to May, or all summer and fall in moist soil of cultivated fields.

One of the first green weeds to appear in the winter in southern Arizona, London rocket usually disappears, except in moist shaded places, when the weather becomes hot. It is a prolific seeder.

Copyright (c) 1972 The Arizona Board of Regents

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