London rocket, Sisymbrium irio, is a herbal plant in the family Brassicaceae. It is an annual herb exceeding three feet in height with open, slender stem branches. The flowers are small with four pale yellow petals. The basal leaves are broad and often lobed, while the upper leaves are linear in shape and up to four inches long. The fruit is a long narrow cylindrical silique which stays green when ripe. The younger pods overtop the flowers. When dried the fruit has small red oblong seeds.
This species is considered a weed in some areas.