Ethephon influences flowering, height, and branching of several herbaceousperennials

Effects of ethephon (2-chloroethylphosphonic acid) were determined on flowe ring, plant height, and branching of Achillea millefolium L. 'Weser River S andstone', Coreopsis verticillata L. 'Moonbeam', Echinacea purpurea Moench 'Bravado', Leucanthemum x superbum Bergmans ex. J. Ingram 'Thomas Killen', Liatris spicata Willd. 'Kobold', Monarda didyma L. 'Blue Stocking', Phlox p aniculata L. 'Mt. Fuji', and Physostegia virginiana Bentham 'Summer Snow'. Spraying ethephon three times at 1000 mg l(-1) (6.92 mM) delayed the flower ing of Echinacea, Monarda, and Physostegia by 6, 7 and 9 days, respectively . Ethephon reduced height by 23, 42, 46, 40, or 46% when applied three time s at 1000 mg l(-1) on Achillea, Echinacea, Leucanthemum, Monarda, or Physos tegia, respectively, compared to that of control plants at anthesis. Effect s of ethephon on the inflorescence and shoot count per pot varied among spe cies. The number of inflorescences per pot was increased by ethephon applic ation to Achillea (36%), Coreopsis (52%), and Phlox (25%), but was decrease d in Echinacea (33%), Leucanthemum (21%) Monarda. (62%), and Physostegia (2 4%). Treatment with ethephon at 1000 mg l(-1) caused necrosis of Monarda fo liage. Inflorescence diameter of Leucanthemum decreased with increasing eth ephon dosage. (C) 2001 Elsevier Science B.V. All rights reserved.