Evaluating herbaceous perennial species as new flowering potted crops

A number of herbaceous perennial species, including Agastache rugosa (Fisch. & Mey.) Kuntze, Corydalis lutea (L.) DC., Laurentia axillaris Lindl. (E. Wimm.), Nepeta subsessilis Maxim., and Oenothera speciosa Nutt. were evaluated for their potential as new flowering potted crops. Agastache and Corydalis seedlings were obtained from a commercial greenhouse. Vegetative cuttings of Laurentia, Nepeta, and Oenothera were taken from stock plants grown under 9-h photoperiod and rooted in a propagation greenhouse. Plants were vernalized at 5 degrees C for 0 and 5 (Agastache, Laurentia, Nepeta, Oenothera), 10 (Laurentia), or 15 (Colydalis, Laurentia) weeks under a 9-h daylength. Following cold treatment, ten plants of each species were grown at 20 degrees C under each of the following photoperiod and lighting treatments: (1) 9-h short day (SD); (2) 16-h long day by day-extension lighting with incandescent lamps (LD) or (3) a 16-h long day with supplemental and day-extension lighting with high pressure sodium lamps (LD+). Only Laurentia had an obligate vernalization requirement and required 10 weeks of cold treatment for complete flowering. Although Laurentia flowered under SD following vernalization, plants required LD or LD+ for commercially acceptable flowering. All other species flowered completely without exposure to cold. Nepeta flowered under LD and LD+ but not under SD following 0 or 5 weeks cold treatment. Oenothera only flowered under LD and LD+ without cold but also flowered under SD following 5 weeks cold treatment. Complete flowering (100%) of Corydalis and Agastache required LD or LD+. Flowering of both Corydalis and Agastache was hastened by 1 week under LD and LD+ as compared to SD for noncooled plants and by 2 weeks for cooled plants. Flower number for all species except Corydalis was significantly greater at anthesis for plants grown with additional supplemental light. All of the species evaluated can be forced to flower out of season, but this study suggests that Laurentia has the most potential for introduction as a flowering potted plant.