Low-Value Trees as Alternative Substrates in Greenhouse Production of Three Annual Species

Abstract

Peat and perlite have served as industry standards in greenhouse substrates for over 50 years. The continued availability of peat, paralleled with its inert characteristics, as well as its ability to stay generally pathogen-free have all contributed to its success in the horticulture industry. Expanded perlite has long been used as an amendment in container mediums to provide air space to container substrates without adding to bulk density or affecting substrate pH and EC. However, due to increased restrictions on the harvesting of peat, as well as fluctuations in fuel prices necessary for shipping, the future availability of peat is a largely unknown factor in greenhouse production. Additionally, growers consider perlite to be a general nuisance due to the lung and eye irritation problems. Because of these problems, researchers have focused on identifying and evaluating possible alternatives to standard substrates. These studies evaluated three possible substrate alternatives for use in greenhouse production, including fresh sweetgum (SG), hickory (H), and eastern redcedar (RC), in addition to WholeTree (WT) substrate. Three greenhouse annual crops (petunia, impatiens, and vinca) were planted in varying ratios of these species mixed with peat. Plants grown with SG and H as amendments did not perform as well as a traditional peat:perlite mix with respect to flower number, growth indices, and plant dry weight. However, plants grown in RC tended to be equivalent to those grown in a traditional mix. Data showed that greenhouse producers could amend their standard greenhouse substrate with up to 50% eastern redcedar with little to no differences in plant growth.