2017 ASHS Annual Conference

Little information exists for producing containerized native North American herbaceous perennials. The objectives of our research were to quantify the growth of eight prairie and woodland herbaceous perennials to controlled-release fertilizers during greenhouse production. Vernalized 50-cell plug trays of wild columbine (Aquilegia canadensis L.), white wild indigo (Baptisia lactea L.), prairie smoke (Geum triflorum Pursh), american alumroot (Heuchera americana L.), great blue lobelia (Lobelia siphilitica L.), bradbury’s monarda (Monarda bradburiana Beck), woodland phlox (Phlox divaricata L.), and pinnate prairie coneflower (Ratibida pinnata (Vent.) Barnhart) were received from a commercial producer. When species displayed signs of active growth, they were individually transplanted into 5.5-inch-wide square containers filled with a commercial soilless substrate individually amended with 0, 1.2, 2.4, 3.6, 4.7, or 5.9 kg/m³ of controlled-release fertilizer (16–2.2–9.1) and irrigated with clear, tempered municipal water. Plants were grown in a glass-glazed greenhouse with an average daily temperature of 23.7 °C and a daily light integral of 14.5 mol∙m^–2∙d^–1. Every other week, pour through leachate tests were performed to measure pH and electrical conductivity (EC) of substrate leachate. Data collected or calculated included height, diameter, shoot dry mass, and relative chlorophyll concentration (SPAD). The influence of CRF fertilization on growth (SDM), development (height and diameter), and relative chlorophyll concentration varied among taxa. For example, white wild indigo, and bradbury’s monarda heights were slightly shorter than unfertilized plants at high CRF concentrations. Alternatively, great blue lobelia height increased as CRF increased up to 3.6 kg∙m^–3. Plant diameters were either unaffected by CRF (white wild indigo, wild columbine) or increased with CRF to 3.6 kg∙m^–3 (great blue lobelia, pinnate prairie coneflower). Great blue lobelia SPAD increased from 24.2 to 50.7 as CRF increased from 0 to 5.9 kg∙m^–3 and pinnate prairie coneflower increased from 25.7 to 52.0. Alternatively, SPAD for columbine and prairie smoke only increased with CRF up to 3.6 kg∙m^–3. Applying 3.6, 4.7 or , 5.9 kg∙m^–3 produced the greatest SDM for pinnate prairie coneflower, great blue lobelia, or bradbury’s monarda, respectively, while prairie smoke, white wild indigo, and wild columbine were unaffected by CRF. There were no clear relationships between growth response to CRF and native habitat. For example, not all prairie plants had greater fertilizer requirements, and some woodland species responded to increasing CRF.