Effect of Cutting Size and Basal Heat on Rooting of Micromeria fruticulosa Stem Cuttings

Micromeria fruticulosa (Bertol.) Grande is a small pulviniform shrub, belonging to the Labiates, and characterized by twisted stems and pink-purple flowers. Endemic to Campania and Sicily (Italy), M. fruticulosa grows from sea level to 600 m altitude. This specie might be considered an excellent native plant for landscape purposes in Mediterranean areas because of its long flowering period, extending from November to June, and its tolerance to heat and drought. The exploitation of wild plants for ornamental purposes implies knowledge on the factors influencing the propagation methods. Root development of stem cuttings of M. fruticulosa was investigated in relation to basal heat and cutting size. Softwood terminal cuttings of a clone grown in Sicily were trimmed to two sizes: short (3 cm) or long (6 cm) length. Propagation was performed in unheated greenhouse covered with clear polyethylene and external 70% shade-cloth. To verify the rooting response to basal heat, half of the cuttings were placed on a basal heated bench (22 ± 2 °C constant temperature) while the remaining were placed on an unheated bench. Acclimatized rooted cuttings were thereafter transplanted into each plastic pot (diameter 16 cm). Plants were thereafter transplanted in the open field and were evaluated for their ornamental value. Basal heat promoted earlier rooting and positively affected adventitious root formation. Six cm long cuttings exposed to basal heat exhibited the best development in terms of number and length of adventitious roots. Flowering plants derived from 6 cm long cuttings exposed to basal heat showed the highest number of flowering branches and flowers per plant.