Laboratory and greenhouse studies were conducted to determine the effect of temperature, solution pH, water stress, and planting depth on broadleaf signalgrass germination. Broadleaf signalgrass seed required removal of the husk for germination. When treated with constant temperature, broadleaf signalgrass germinated over a range of 20 to 35 C, with optimum germination occurring at 30 and 35 C. Onset, rate, and total germination (87%) was greatest in an alternating 20/30 C temperature regime. Germination decreased as solution pH increased, with greatest germination occurring at pH values of 4 and 5. Germination decreased with increasing water potential, and no germination occurred below − 0.8 mPa. Emergence was above 42% when seed were placed on the soil surface or buried 0.5 cm deep. Germination decreased with burial depth, but 10% of broadleaf signalgrass seed emerged from 6.0-cm depth. No seed emerged from 10-cm depth. These data suggest that broadleaf signalgrass may emerge later in the season, after rains, and could germinate rapidly and in high numbers. These attributes could contribute to poor control later in the season by soil-applied herbicides or allow broadleaf signalgrass to emerge after final postemergence treatments were made.
Nomenclature: Broadleaf signalgrass, Brachiaria platyphylla (Griseb.) Nash BRAPP.