Teresa Cerny-Koenig

Characterizing fertilizer and media pH requirements for greenhouse production of Intermountain West native herbaceous perennials

Colorado blue columbine (Aquilegia caerulea James [Ranun-culaceae]), Palmers penstemon (Penstemon palmeri Gray [Scrophulariaceae]), and Russian sage (Perovskia atriplicifolia Benth. [Lamiaceae]) were treated with 5 rates of a standard water-soluble fertilizer (0, 50, 100, 200, 400 mg/l [ppm] nitrogen [N]) to determine the optimum concentration for the production of plants in greenhouse containers. Plant quality and shoot dry matter increased while root:shoot dry matter decreased linearly with fertilizer concentration up to 200 ppm N for all species in a spring trial. Responses to fertilizer concentrations up to 400 ppm were less consistent in a fall trial. The response of gooseberryleaf globemallow (Sphaeral-cea grossulariifolia (Hook. & Arn.) Rydb. [Malvaceae]) and Rocky Mountain penstemon (Penstemon strictus Benth. [Scro-phulariaceae]) to 5 media pHs (average 4.5, 5.4, 6.0, 6.9, and 8.3) was also evaluated. During the summer and, for P. strictus, spring, plants growing in the lowest pH did not perform as well as in the intermediate pH treatments. Plant performance in the high pH treatment was consistently lower than in the intermediate pHs for both species at all times. Overall, results indicate these native species can be grown using fertilizer concentrations (200 ppm) and media pHs (5.1 to 7.2) similar to other common greenhouse plants.