Abstract Foliar applications at 3, 6, and 9 kg ai/ha of 10 plant growth inhibitors were evaluated on 2- to 3-year-old seedlings of green ash (Fraxinus pennsylvanica Marsh.) and silver maple (Acer saccharinum L.) under greenhouse conditions. Effective retardation or inhibition without terminal injury was obtained on silver maple with the high rates of ancymidol and MH and the low rate of fluoridamid. Ancymidol at 6 and 9 kg ai/ha, Krenite at 9 kg ai/ha and the combination, chlorflurenol + maleic hydrazide (MH) at 3 and 6 kg ai/ha, gave the best control of stem elongation on green ash without excessive injury.