Shepherd's purse is a weedy annual with one to several erect, slender, simple to branched stems from 10-50 cm high. The stems and leaves are covered with stiff, straight hairs, at least some of which are divided to appear somewhat like a starburst. The basal leaves form a rosette of oblanceolate leaves from 3-6 acm long. They are petiolate and have nearly entire to pinnatifid leaves, the terminal lobe measuring much larger than the lateral lobes. The leaves become reduced in size upwards on the stems. The stem leaves are sessile and clasping and are lanceolate to oblong-oblanceolate in shape with lightly toothed margins.
The many white flowers are found in elongate, bractless racemes. The slender pedicels are spreading (See photos.) and measure from 7-15 mm long. The sepals are about 2 mm long. The petals are patulate-obovate in shape and measure from 1.5-4 mm long. The strongly flattened silicles are triangular-obcordate in shape (See photo above.) and measure from 4-8 mm long and up to 3-5 mm long. The flowers contain 6 stamens. The silicles are widest and shallowly notched at the tips. The silicles contain many tiny seeds, and shepherd's purse self seeds readily, making it hard to contain even though the plants are easily pulled.
Shepherd's purse may be found in disturbed places such as roadsides, gardens, vacant lots and fields. It may be found from the lowlands up to subalpine habitats.
Shepherd's purse is a weedy species native to Europe that is found over much of North America.