Rooting of Kalmia latifolia Stem Cuttings with Three Dosages of Hormones

Kalmia latifolia L. (Ericaceae) is a native evergreen shrub or small tree with attractive flowers and the difficulty in cutting propagation limited its popularity in landscape. Three dosages of hormones were applied to stem cuttings of Kalmia latifolia ‘Elf’ and ‘Starburst’ from November 2013 to June 2014. Cuttings were sprayed with 25 mg·L^-1 K-IBA 1 month before taking cuttings (pretreatment), then prepared with liquid K-IBA and powdery Hormodin at 1,000, 3,000, and 8,000 mg·L^-1, and finished with 1,000, 3,000, and 8,000 mg·L^-1 K-IBA after 4 months for cuttings with calla. For both cultivars, pretreatment did not improve the rooting of stem cuttings. It is possible that plants did not have too much activity during winter months to absorb the hormone. Timing of pretreatment should be further investigated. Rooting occurred on stem cuttings of ‘Elf’ and ‘Starburst’ under 8,000 mg·L^-1 K-IBA treatment with lower rooting percentage of 12.5% and 6.3% respectively, which indicated that rooting of Kalmia was very difficult and required higher hormone concentrations. Majority of stem cuttings did have calla and sequentially treated with third hormone treatments. ‘Elf’ and ‘Starburst’ cuttings treated with 1,000 mg·L^-1 K-IBA produced the rooting percentage of 75% and 100%, respectively. Further studies should address the better timing and methods for rooting hormone application of Kalmia latifolia stem cuttings.