Fertilization Rates Affect Color Intensity and Flower Earliness in Coleus in the Landscape

Production practices can affect the landscape performance of ornamental plants. Nutrient management, especially nitrogen (N) and phosphorus (P) may affect leaf coloration and timing of flowering, two quality concerns in the container production of coleus (Solenostemon scutellarioides (L.) Codd). In the first experiment, rooted cuttings of ‘Mint Mocha’, ‘Indian Summer’, ‘Henna’, ‘Red Head’, ‘Trusty Rusty’, and ‘Red Ruffle’ were grown in a greenhouse and fertilized with 0, 70, 140, 280, or 420 mg·L^-1 N or 0, 0, 6.2, 12.4, 24.8, and 49.6 mg·L^-1 P for 8 weeks. Plant growth was evaluated by plant size and biomass. Plant quality was evaluated by visual quality ratings and leaf color analyses. In the second experiment, ‘Red Head’ and ‘Trusty Rusty’ were grown under different N and P regimes that produce the most vivid color for 6 weeks and then planted in landscape beds to evaluate flower earliness in these plants. Results from the first experiment suggest that leaf color intensity decreased significantly when N rate increased to 280 mg·L^-1 though larger plants were obtained at this rate. Landscape evaluation indicated that earliness of flowering was not affected by different fertilization regimes within the range to produce quality coleus plants of the tested varieties.