Germination Characteristics of Italian Thistle (Carduus pycnocephalus) and Slenderflower Thistle (Carduus tenuiflorus)

Abstract

Seed germination of Italian thistle (Carduus pycnocephalusL.) and slenderflower thistle (Carduus tenuiflorusCurt.) was rapid and high, with no strong requirements for afterripening. Both species germinated at a wide range of alternating temperatures from −2 to 40 C. Their germination-temperature profiles were similar, with Italian thistle germinating over a slightly wider range of temperatures. The achenes of both species have abundant mucilage. This mucilage, by improving water retention, tended to increase germination on the surface of clay soil.