Characterization of whole pine tree substrates for adventitious rooting of cuttings and initial growth of seedlings
Processed whole pine ( Pinus taeda L.) trees have been extensively evaluated to supplement peatmoss and pine bark usage in container substrates for greenhouse and nursery crop production. The suitability of whole pine tree (WPT) substrates for crop propagation has not been investigated. Demonstrating the versatility of WPT substrates is essential to expanding their commercial availability and use. The objective of this work was to evaluate WPT substrates for stem cutting and seed propagation of ornamental crops, and to identify factors affecting root development. Stem cutting and seedling root development was evaluated in WPT and traditional (peatmoss and pine bark) substrates. In the first study, stem cuttings of Chrysanthemum, Cupressocyparis, Euonymus, Evolvulus, Ligustrum, Persicaria, Rosa, and Salvia were set in whole pine tree and pine bark substrates. Rooting percentage was similar among substrates for each species, but root growth increased with the addition of peatmoss. In the second study, a phytotoxicity assessment of aged and fresh WPT substrates was conducted using a Phytotoxkit and a seedling growth test. Using the Phytotoxkit, seed germination rate and seedling root growth was similar for aged WPT and peatmoss. Fresh pine needles had an inhibitory effect on seed germination and seedling growth. Using the seedling growth test, lettuce, oat, and tomato seed emergence rate was similar for aged WPT and a peatmoss substrate. Root development was greatest in a peatmoss substrate compared with pine bark and aged and fresh WPT. In the final study, the effect of WPT particle size on seedling and stem cutting root development was evaluated. Processing WPT into finer particle sizes resulted in decreased air space and increased container capacity, but did not affect stem cutting or seedling root growth. Overall, root development was greater in peatmoss substrates compared with WPT substrates. Whole pine tree substrates can be used for germinating seeds and rooting stem cuttings. Differences in seed germination/emergence rate and seedling root length could not be attributed to phytotoxic compounds in WPT substrates. Nutrient availability and retention properties of WPT substrates during propagation should be further evaluated.