Pygmyflower is becoming increasingly abundant in conservation-tillage cropping systems of the Canadian Prairies. Increased knowledge of pygmyflower biology would facilitate development of integrated programs for its control. A controlled environment study was conducted to determine the combined effect of various soil temperature and soil water levels on pygmyflower emergence. Pygmyflower emerged at soil temperatures ranging from 10 to 25 C with optimal emergence at 15 C. Emergence was inhibited completely at 5 or 30 C. Pygmyflower emergence markedly declined as soil water content decreased. At progressively lower soil water levels of − 0.03, − 0.28, − 0.53, − 0.78, − 1.03, and − 1.53 MPa, pygmyflower emergence at 15 C was 71, 50, 49, 29, 24, and 15%, respectively. The interaction of warm and dry soils caused the greatest inhibition of pygmyflower emergence. Rate of pygmyflower emergence was reduced greatly by either lowering soil temperature or reducing soil water content. A decrease in soil temperature from 25 to 10 C increased the time to reach 50% emergence (ET50) by 9 to 14 d, whereas a decrease in soil water content from − 0.03 to − 1.53 MPa increased ET50 by 7 to 16 d. Results suggest that pygmyflower may pose the greatest problem in winter crops or early-planted spring crops. Information gained in this study will contribute to the development of an improved pygmyflower management program in annual cropping systems.
Nomenclature: Pygmyflower, Androsace septentrionalis L. ANSSE.