Abstract
Saw palmetto is a palm of high ornamental and land restoration value with the potential for commercial production as a result of its phytotherapeutic properties. It is native to the southeastern United States, where green- and silver-leaved forms are found. Nursery production of saw palmetto is based on seed germination. However, seed germination is slow and uneven. Based on communications with nursery growers, deeper seed placement in the substrate yields taller seedlings at marketable size in a shorter period. We investigated the influence of sowing seed depths (1, 2, 4, 6, and 8 cm) on the germination and seedling growth of silver and green forms of saw palmetto. Green saw palmetto seeds germinated 60 days earlier than silver saw palmetto seeds, although final germination percentages were similar (84% and 82%, respectively). Sowing depth influenced significantly the required seed rate overage, with shallow depths (1 cm) necessitating a 30% to 45% increase in seed quantity to compensate for reduced seedling production, whereas sowing at 4 cm reduced overage to 5% to 6%, optimizing seed use and reducing costs. Differences in growth parameters 1 year after sowing were statistically significant for 1-year-old seedlings, with silver plants performing better than green ones. Major differences occurred between the 1- and 8-cm sowing depths with regard to seedling and root length. Plants from seeds sown at 8 cm showed increased plant height and width, and reduced root length compared with those sown at 1 cm. Vigor indices of plants from deeper sowing (2, 4, 6, and 8 cm) were higher than those sown at 1 cm. We conclude that green saw palmetto seeds germinated earlier than silver, but final germination percentages were similar. In addition, sowing at 4 cm optimized seed use and costs, whereas deeper sowing improved plant vigor and growth but reduced root length.