Vernalization characteristics in Lavandula × intermedia

Lavandula × intermedia ‘Super Sevillian Blue’ has been previously reported to be a vernalization-type plant. However, the vernalization characteristics in L. × intermedia still remain unknown. Thus, effects of vernalization, devernalization and revernalzation treatments on flowering in L. × intermedia cuttings were studied. Firstly, flowering of L. × intermedia cuttings was investigated under two devernalization treatments, namely, two cold treatment (CT) periods (9 and 12 weeks) with 5 days of heat treatment (HT) to clarify effect of devernalization treatment. Days to visible buds (VB) under devernalization treatments increased compared with those under vernalization treatments. The rates of budding plants and flowering plants under devernalization treatments significantly decreased as compared with those under corresponding vernalization treatments. Secondly, L. × intermedia cuttings were exposed to additional 3 weeks CT after devernalization treatment (revernalization treatment) to clarify effect of revernalization treatment. The rates of budding plants and flowering plants under revernalization treatments were 100%, which were the same as those under vernalization treatments. These results suggest that the additional CT in L. × intermedia plants under reverenalization treatments induce budding and flowering by negating HT under deverenalization treatments. Thus, we conclude that cuttings of L. × intermedia ‘Super Sevillian Blue’ have typical vernalization characteristics such as vernalization, devernalization and revernalization phenomena, like herbaceous plants, although L. × intermedia is a woody plant.