The 2012 ASHS Annual Conference

Rhododendron calendulaceum (Flame Azaleas) have many desirable horticultural traits but are often challenging to grow.  In this study, we investigated Flame Azalea seedling growth in response to growing media. Seeds collected from Hooper Bald, Graham County, N.C., were germinated in 96 cell flats and grown for a period of 12 weeks in varying media. Varying ratios of peat, perlite, coir, and sand were used to formulate the media used in the experiment. A total of four separate media mixtures with three replications of each, were used to evaluate early seedling growth to better inform existing propagation protocols.  Seedling emergence timing and percentage was recorded. Shoot length, root length, shoot/root ratio, and true leaf area were also evaluated using computer-aided analysis of 30X digital images of randomly sampled seedlings. Significant differences in seedling growth parameters were detected in response to the different media treatments. Emergence of seedlings ranged from 57% to 69% across the treatments, in line with prior work showing a germination rate of 61% for this seed lot. Treatment 1, consisting of a media mixture of 4:2:1 Peat, Sand, and Perlite, had the lowest emergence percentage but exhibited significantly larger root growth, total plant growth, and leaf area when compared to the other three treatments. Our results provide useful information for nurserymen and propagators interested in the Flame Azalea.