Preemergence Weed Control in Container-grown Herbaceous Perennials

Abstract

During the 2003 season, preemergence herbicide was applied to twelve container grown herbaceous perennials and woody plants and evaluated for weed control, phytotoxicity, and effect on plant growth. The herbicide and rates were: Flumioxazin (Broadstar) 113.5 g (label rate), 227 g and 454 g a.i./A. Herbicides were applied to Buxus microphylla `Winter Gem', Cytisus purgans `Spanish Gold', Festuca ovina glauca `Elijah Blue', Hakonechloa macra `Aureola', Lonicera tatarica `Arnold Red', Pachysandra terminalis `Green Sheen', Hydrangea arborescens `Annabelle', Mahonia aquifolium, Phalaris arundinacea `Picta', Carex buchananii, Cerastium tomentosum, and Achillea millefolium `Red Beauty'. Weed control was excellent at all rates and controlled at least 99% of all weeds. No phytotoxicity symptoms were apparent on Mahonia, Buxus, Cytisus, Festuca, Hakonechloa, Pachysandra or Phlaris. Phytotoxicity resulted on some of the other plants. Carex had smaller plants (dry weights) at all rates. Cerastium had severe phytotoxicty at the 227 g and 454 g rates and moderate stunting at the recommended label rate, 113.5 g. Hydrangea became chlorotic and stunted at the 113.5 g rate and some fatal toxicity ocurred at the 227 g and 454 g rates. Phytotoxicity resulted on Lonicera at all rates and ranged from mild chlorosis in leaf veins (113.5 g rate) to plant death (454 g rate). Achillea at the 113.5 g rate only resulted in stunted plant growth while the 227 g and 454 g rates resulted in severe phytotoxcity and plant death.