In the Netherlands two ecotypes of Sonchus arvensis L. are found: var. arvensis (arable type) on arable land and var. maritimus G. F. W. Mey. (coastal type) in coastal dunes. The author’s experiments show that these differ in their response to temperature and moisture during germination. The coastal type germinates faster than the arable type and its germination occurs already at lower temperatures. Furthermore the coastal type germinates at lower moisture tensions. From these experiments it appears that the coastal type is better adapted to the germination conditions prevailing in the dune habitat. The germination characteristics of the arable type fit in well with its natural distribution pattern.