(61) Nutrient Management of Common Herbaceous Perennial Plantings in Southern Landscapes

Abstract

While herbaceous perennials continuously gain popularity in southern landscape plantings, the nutrient requirements of many species in this group are still unknown. The business goal of lawn and garden care companies emphasizes aesthetic value of the urban landscape. Improper nutrient management, such as the overapplication of fertilizers, is inefficient and may result in increased pest problems and risks of contaminating ground and surface waters by nutrient runoff. Seven herbaceous perennials (lantana, rudbeckia, purple cone flower, daylily, mexican heather, cigar plant, and guara) were planted in simulated landscape beds. Fertilizers applied included one or two OsmocotePlus 16-8-12 tablets (7.5 g), OsmocotePlus 15-9-12 (5 months) at 0, 33, 66, and 131 g/m2 at planting, or applying OsmocotePlus 15-9-12 (5 months) 33 g/m2 or one OsmocotePlus tablet at the time of planting plus another 33 g/m2 topdressing after flowering. Plant growth of rudbeckis, purple cone flower, and lantana were highest at 131 g/m2 applied at planting, but resulted in similar overall plant quality as with 33 or 66 g/m2 treatments. Daylily growth was similar across fertilization treatments, and overall quality decreased at high fertilization rates with more severe daylily rust observed on these plants. Applying one OsmocotePlus 7.5-g tablet resulted in similar plant quality with applying OsmocotePlus 33 and 66 g/m2, but significantly reduced the amount of fertilizer used. Additional topdressing after flowering did not further increase plant quality in fall, but may affect the overwintering survival of perennial plants.