What is "sisymbrium irio"

London \Lon"don\, n. The capital city of England. London paste (Med.), a paste made of caustic soda and unslacked lime; -- used as a caustic to destroy tumors and other morbid enlargements. London pride. (Bot.)

1. A garden name for Saxifraga umbrosa, a hardy perennial herbaceous plant, a native of high lands in Great Britain.

2. A name anciently given to the Sweet William.
   --Dr. Prior.

   London rocket (Bot.), a cruciferous plant ( Sisymbrium Irio) which sprung up in London abundantly on the ruins of the great fire of 1667.

Sisymbrium irio, known as London rocket, is a 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. The common name "London rocket" comes from its abundance after the Great Fire of London in 1666. However, Dr E J Salisbury, in his study of the bombsites of London after the Great Fire of 1940, "failed to find a single specimen, nor has any other reliable observer reported it", according to R. S. R. Fitter.

This species is considered a weed in some areas.