Rooting Response of Deciduous Azaleas, Rhododendron Section Pentanthera, Stem Cuttings to Mist Regimes and Media Mixes

Abstract

Rooting of stem cuttings of Escatawpa azalea, Rhododendron austrinum (Small) Rehder ‘Escatawpa’, was evaluated on four harvest dates in six media mixes under two mist regimes. Data was collected at 2 week intervals from 6 to 12 weeks after date of stick. Cuttings subjected to the lower mist duration (9 s) produced consistently superior root development than those subjected to the higher mist duration (12 s) both at the same 10 min interval. All media mixtures consisted of 50% pine bark by volume. In the series of media mixes evaluated, the remaining 50% of volume progressed from 50% perlite to 50% peat in 10% increments. The media mixture 2 perlite : 3 peat : 5 pine bark (by volume), produced superior results earlier in the evaluation schedule than the other media mixtures. The majority of cuttings were rooted at 6 weeks, but rooting percentages increased as harvest date progressed from 55% at 42 days to 89% at 84 days after cuttings were stuck. Harvest date was a repeatedly important factor in the analysis of media and mist allowing for meaningful evaluation of the schedule of development of cuttings in different growing conditions within our results. To document the variation across taxa to these propagation protocols, cuttings from 20 cultivars of deciduous azaleas were given the lower mist regime and stuck in the best performing media mixture. Under these protocols, tetraploids and complex multi-generational hybrids achieved superior root ratings compared to diploids, straight species selections, and F-1 hybrids.