Herbaceous Perennial Seed Germination and Seedling Growth in Biochar-amended Propagation Substrates

The first objective of this study was to assess the effects of coconut shell biochar in propagation substrate on seed germination and seedling growth of Coreopsis grandiflora (Hogg ex Sweet) 'Early Sunrise', Leucanthemum xsuperbum (Bergman ex J. Ingram) 'Silver Princess', and Eschscholzia californica (Cham.). Cornell seed germination mix was amended with the biochar (0%, 5%, 10%, 20%, or 40%, v/v). Seed germination and seedling growth were determined during a 21-day period in two germination rooms. This particular biochar amendment did not affect final germination percentage for any of the species. All three species had seedling shoot and primary root length growth with low to moderate positive correlation (r = 0.33-0.54) with coconut shell biochar amendment volume. Coreopsis seedling dry weight was significantly higher with 40% biochar than the control (P <= 0.05). The second objective of the study was to compare digitally collected data with manually collected data. Two-dimensional scans of Coreopsis and Leucanthemum seedlings were collected. Seedling dry weight (mg) and seedling length (mm) predicted seedling two-dimensional area for Coreopsis (R-2 = 0.73, P < 0.001) and Leucanthemum (R-2 = 0.87, P < 0.001). Digitally traced shoot and root lengths were strongly positively correlated (r = 0.99-0.97) with manual ruler measurements, suggesting that digital imaging could replace manual length measurements. The results of this study suggest inclusion of this particular coconut shell biochar in seed germination, and establishment substrates can have neutral or positive effects on herbaceous perennial germination and establishment.