Abstract Early spring flowering of Forsythia × intermedia Zab. (forsythia) and growth of Cydonia sinensis Thouin (Chinese quince) can be prevented by over-wintering container grown plants under microfoam thermo-blankets covered with black, white, or clear polyethylene (poly) spray painted in late winter and diluted white latex paint. Although covering microfoam with black poly may extend its useful life and suppress the growth of winter weeds, it appears damaging to X Cupressocyparis leylandii A. J. Jacks & Dallin. (Leyland cypress) and Prunus laurocerasus L. (cherry laurel). Ilex crenata Thunb. (Japanese holly), Viburnum rhytidophyllum Hemsl. (leathe leaf viburnum) and Euonymous alata Thunb. ‘Compacta’ (dwarf winged euony-mus) responded equally well to all treatments. Thermo-blankets protected the roots from minimum killing temperatures but highest maximum temperatures were measured under polyethylene foam and microfoam covered with clear or woven clear polyethylene.