Hormones Improved Rooting of Zelkova serrata Softwood Stem Cuttings

Zelkova serrata is a deciduous tree in Ulmaceae introduced from East Asia and has been widely used for bonsai, shade tree or park landscape because of its attractive habit, foliage colors, and drought tolerance. Its disease/pest resistant features placed it as a great substitute of American elm. To better regenerate Zelkova serrata for market demand, softwood stem cuttings treated with rooting hormones at various concentrations were investigated in 2013. Terminal cuttings from one year-old seedling plants were dipped into K-IBA, K-NAA at 1000, 3000, 8000 mg·L^-1 and dusted with powdery Hormodin #1, #2, #3. Rooting hormones should be applied for rooting of Zelkova serrata cuttings and no root was found under the control. The highest rooting percentage of 40.6% was under the treatment of Hormodin #2, which also yielded the highest root length of 9.0cm. Liquid K-IBA was significantly more effective on rooting than that of K-NAA. Under 1000 mg·L^-1 treatment, K-IBA produced 31.3% of rooting with root length of 8.4cm, while K-NAA 15.6% and 2.3cm. Effectiveness of hormone concentration depended on the application methods. The concentration of 1000 mg·L^-1 should be recommended for liquid hormones and 3000 mg·L^-1 for powdery hormones. Although rooting hormones induced the rooting of softwood cuttings of Zelkova serrata, further studies should focus on semi-hardwood and hardwood cuttings and improve Zelkova rooting percentage and quality.