Lactuca tatarica (L.) C. A. Mey., a blue-flowered Lactuca of the Asiatic and Southeast- European steppe, was found in 1961 as an alien at Rotterdam, where it was more or less naturalized, growing between the basalt-blocks of the embankment of a harbour. Since the early years of the 20th century it has established itself in several places on the coast of the Baltic, where it is becoming part of the natural vegetation. It was also found in a few localities on the coast of England, Scotland and Ireland. As appears now, Lactuca tatarica was already found in 1942 at Doesburg (Gelderland), but was then misidentified as Lactuca perennis.