Seed Production of Field- and Greenhouse-Grown Herbaceous Ornamental Plants: Flowering and Pollinator Effects

Abstract

Seeds of herbaceous ornamental accessions conserved by the USDA National Plant Germplasm System (NPGS) are traditionally produced in summer field cages with honey bees (Apis mellifera) when pollinators are required. Efficient methods to produce high-quality seed in greenhouses may allow for year-round seed production. Flower quantities and effects of pollinators on number and weight of seed produced were studied in field cages and greenhouses at the Ornamental Plant Germplasm Center in 2003 in a randomized complete-block experiment. Honey bees, bumblebees (Bombus impatiens), or blue bottle flies (Diptera calliphoridae) were used as pollinators. Field cages and greenhouse compartments with no pollinator were controls. Cultivars used were Antirrhinum majus `Gum Drop', Coreopsis tinctoria `Plains Bicolor', Dianthus chinensis `Carnation' (NPGS accession NSL 15527), Rudbeckia hirta `Indian Summer', and Tagetes patula `Jaguar'. Seeds were harvested, cleaned, weighed, and 100-seed weights calculated. On average Antirrhinum, Dianthus, Rudbeckia and Tagetes produced more flowers in greenhouses, Coreopsis produced more flowers in the field. Coreopsis and Rudbeckia produced more seed per flower on average with field pollination by honey bees, Antirrhinum and Dianthus produced most with bumblebees in the field, and Tagetes produced most with blue bottle flies in the greenhouse. Each genus had similar 100-seed weights on average in all treatments. Results show pollinators other than honey bees are useful for herbaceous ornamental seed production and that seed production in greenhouses may be an alternative method for seed production of herbaceous ornamentals.