ASHS 2025 Conference

The growing demand for sustainable landscapes and eco-friendly practices has significantly influenced consumer interest in native plant species. Agastache spp. is a xeric species naturally acclimated to the Rocky Mountain region and is valued for its ornamental flowering and exceptional landscape resilience, particularly in arid environments. However, one challenge is the limited availability of saleable plants due to challenges during asexual propagation, in particular, successful adventitious rooting of cuttings. Therefore, a study was conducted to evaluate the impact of different indole-3-butyric acid (IBA) rooting hormone concentrations on root initiation and development of Agastache ‘Coronado Red’. A total of 72 uniform stem cuttings were collected and 18 stems were treated with one of four experimental treatments that included, control (water), 1000, 3000, and 8000 ppm IBA concentrations. Cuttings were stuck in 72-cell trays and placed on a propagation misting bench, using a randomized complete block design. Destructive data collection occurred on a bi-weekly basis, with three collections. The experiment was repeated over the course of two production seasons. Two weeks after sticking, while callus initiation was present on cuttings for all treatments, an increase in both the number of primary roots and root length was observed as the concentration of IBA increased. For example, the number of primary roots was greatest for cuttings provided the IBA concentration of 8000 ppm (16) compared to the control (0.2) and IBA concentrations of 1000 (3.4) and 3000 ppm (6.3). Similarly, length of the longest root was 1891%, 144%, and 62% greater under the IBA concentration of 8000 ppm compared to the control and IBA concentrations of 1000 and 3000 ppm, respectively. Stem length and the number of nodes were similar for all treatments. These results indicate that higher IBA concentrations promote root initiation and growth as early as two weeks after sticking for Agastache ‘Coronado Red’. While results from the present study indicate that an IBA concentration of 8000 ppm is optimal for early establishment of Agastache ‘Coronado Red’ cuttings, future research is required to determine propagation strategies for other cultivars.