ECOLOGICAL LIFE-CYCLE OF THLASPI-PERFOLIATUM AND A COMPARISON WITH PUBLISHED STUDIES ON THLASPI-ARVENSE

Thlaspi perfoliatum L. is an introduced winter annual that grows in waste places, but it is not a troublesome agricultural weed. Seeds are dormant at maturity in spring, afterripen during summer and germinate in autumn. Non‐dormant seeds that fail to germinate in autumn are induced into secondary dormancy by low winter temperatures and cannot germinate the following spring. These seeds afterripen during summer and germinate in autumn if conditions are suitable. Vernalization is not an absolute requirement for flowering. However, it shortens the time to flowering, and vernalized plants produce many more flowers and seeds than non‐vernalized plants. Results from studies on seed germination and flowering of T. perfoliatum are compared to published studies on the life cycle of Thlaspi arvense L., an introduced species that is a serious agricultural weed which behaves both as a winter and a summer annual. Copyright © 1979, Wiley Blackwell. All rights reserved