Effects of cutting size and exogenous hormone treatment on rooting of shoot cuttings in Norway spruce (Picea abies (L.) Karst.)

The effects of cutting length, cutting diameter, and exogenous hormone pre- treatment on rooting were studied in comparative experiments to improve the efficiency of cutting propagation in Norway spruce. The results showed that cutting length, diameter, and the interaction between cutting length and diameter significantly affected rooting efficiency. Higher rooting efficiency was obtained by cuttings of 0.3-0.4 cm diameter and 9-12 cm length. Hormone type significantly affected all measured rooting traits, and moderately higher measurements were observed in the indole butyric acid treatment than those of the control, whereas all measurements in the a-naphthalene acetic acid treatment were significantly lower than those of the control, which may have been an inhibitor of Picea abies in stem cuttings. The cutting size effect on rooting efficiency is discussed and an optimal cutting size is suggested, which provide valuable information for propagating Norway spruce.