Sisymbrium irio aka London Rocket

Sisymbrium irio is also known as London rocket. It belongs to the mustard family, Brassicaceae. North Carolina State Extension calls it an annual weed. Kew's supplied record instead lists it as a perennial. Its native range spans Europe, western and central Asia, and northern Africa. Kew also lists Ethiopia as part of that range. It now grows in the southwestern United States. It grows in the Great Lakes region too. It lives along roads, in fields, and on walls. It also grows at desert sites and on disturbed ground.

Plants grow fast, with thin, open stems that stand upright. They often reach about 1.7 feet (0.51 metres). Taller plants can reach 3 feet (0.91 metres). Stems branch near the base and may have purple tones. Most of each stem is smooth. Sparse hairs may grow on the lower parts. Green leaves grow in an alternate pattern along the stems. This means they grow at staggered points, not in pairs. Basal leaves, at the base, reach about 0.5 feet (0.15 metres) long. They have a clear midvein and may have lobes. Upper leaves are shorter and less wide than lower leaves.

Small flowers grow in racemes, or clusters, at branch tips. They range from pale to bright yellow. Each flower has both male and female organs. Insects move pollen between the flowers. Flowers appear in spring, when the plant matures early. The fruit is a slim, rounded pod called a siliqua. Pods point up along the upper stems. They stay green as they ripen. Once ripe, they split to show small red seeds. Plants grow from seed, and summer heat can kill them.

London rocket grows in full sun or part shade. It accepts sand, loam, and clay across a broad pH range. It suits moist soil but copes with dry spells. North Carolina State Extension lists USDA zones 8a through 10a. Its main landscape risk is that it can displace native plants. Early spring growth gives it a head start over wildflowers. It can host insects and diseases that harm mustard-family crops. Remove plants before seeds ripen to help reduce later growth. Control can take time, and plants can regrow after fire.

People eat young leaves raw or cooked. Their hot taste limits use. People also eat raw flowers and raw or cooked seeds. Ground seeds mixed with water can make gruel or a drink. Plants For A Future records traditional throat and chest remedies. It also lists seed remedies. These records do not prove that such uses are safe or work. That source reports no known hazards. It does not show that the plant is safe for pets.