Clear and White Plastics for Freeze Protection of Landscape Plants in the Southern to Mid-Atlantic Region

Abstract

Rapid, wide fluctuations in winter temperatures in Mid-Atlantic and Southern states can result in severe damage to container grown landscape plants. Freezes on Christmas Day, 1983 and January 21, 1985 left nurserymen in this region with multimillion dollar losses and an interest in low-cost freeze protection methods. This study examines the cold protection properties of white copolymer and clear poly 6 mil plastics for covering unheated propagation hoop houses and for wrapping container growing beds. Soil, canopy, house ambient and outside temperatures were collected by computer on 15 minute intervals for a 3 month period. Diurnal temperature fluctuations were 1.5 to 2 times greater in clear poly than white copolymer. Double layer plastic coverings maintained minimum soil and canopy temperatures significantly higher than single layer structures. White copolymer wrapping of growing beds afforded root protection to Asian jasmine (Trachelospermum asiaticum Lem.) and Burford holly (Ilex cornuta Lindl ‘Burford Nana’) with some border damage; Wiltonii juniper (Juniperus horizontalis Moench. ‘Wiltonii’) did not need covering. White copolymer offers greater freeze protection at a lower cost.