Palmer Amaranth Flowering In Early April

JACKSON, TENN.

   Much of the Palmer amaranth that is now 3 to 5” tall is flowering. Quite a few folks have asked what the reason is for this early flower. The Palmer amaranth has been triggered to flower by the short day length of March and now early April. Quite literally the Palmer amaranth that has emerged thinks it is late August or September. Palmer amaranth that we are most familiar with emerges from late-April through June. June 21st has the longest amount of day length in a year. After that date the length of daylight becomes shorter. Most of the Palmer but not all will flower as the days get shorter in July and August.

   Does this flowering Palmer causes any issues as far as management? I have often worked with small flowering pigweed in the greenhouse during the winter. In that research I have found from time to time that the plant growth regulating herbicides will provide inconsistent control. The burning type herbicides like paraquat, atrazine or even the PPOs like fomesafen or Sharpen seem to provide more consistent control of small flowering Palmer. Δ

DR. LARRY STECKEL: Extension Weed Specialist, University of Tennessee