Henbit is increasing in abundance in western Canada, and control recommendations are largely limited to herbicides. Increased knowledge of henbit biology may allow the development of more integrated control programs. A controlled environment study was conducted to determine the combined effect of various soil temperature and soil water levels on the emergence of henbit. Henbit emerged at soil temperatures ranging from 5 to 25 C, but the highest emergence of 81 to 83% occurred at 15 to 20 C. Henbit emergence declined as soil water content decreased. The interaction of cool and dry soils caused the greatest inhibition of henbit emergence. At progressively lower soil water levels of −0.03, −0.28, −0.53, −0.78, −1.03, and −1.53 MPa, henbit emergence was 78, 61, 64, 40, 38, and 11% at 10 C, respectively. Rate of henbit emergence was affected less by soil water than by soil temperature. A decrease in soil water content from −0.03 to −1.53 MPa increased the time to reach 50% emergence (ET₅₀) by 1 to 5 d, whereas a decrease in temperature from 25 to 5 C increased the time to reach ET₅₀ by 13 to 16 d. The implications of these results in terms of improved management of henbit are discussed.

Nomenclature: Henbit, Lamium amplexicaule L. LAMAM.