Comparison of Aged and Fresh WholeTree as a Substrate Component for Production of Greenhouse-Grown Annuals

Abstract

Abstract WholeTree (WT) is a potential renewable greenhouse substrate component created by chipping and milling all aboveground portions of a pine tree (Pinus taeda L.). While research regarding the viability of WT as an alternative substrate component is widely available to growers, the potential benefits of aging WT remain unclear. The growth of Dreams White petunia (Petunia ×hybrida ‘Dreams White’) and Little Hero Yellow marigold (Tagetes patula ‘Little Hero Yellow’) in 1:1 (by vol) fresh WT:peat (FWTP) and 1:1 (by vol) aged WT:peat (AWTP), as well as physical properties of AWTP and FWTP were evaluated. For Experiment 1, AWTP had 17.6% particles greater than 3.2 mm as opposed to 12.4% for FWTP. In Experiment 2, this trend was reversed with 8.1% of AWTP particles greater than 3.2 mm and 20.4% for FWTP. For Experiment 1, AWTP had 90.5% total porosity (TP) as compared to 94.4% with FWTP. Air Space (AS) for AWTP was less than FWTP; AWTP had 10% more container capacity (CC) than FWTP. Bulk Density (BD) was similar in Experiment 1. There was no difference in TP in Experiment 2; however, all other physical properties followed a similar trend to Experiment 1. In both experiments marigolds grown in AWTP generally had a lower leachate pH and a higher EC than those grown in FWTP; a trend which was similar in petunia although differences were not present throughout the entire study. Marigolds grown in AWTP had 33% more blooms and 44% greater dry weight than those grown in FWTP, a trend similar in petunias. Aged WT in this study provided a more suitable substrate component for greenhouse grown marigolds and petunias than fresh WT.