Privet is one of the largest single crops in Danish nursery production, used for hedges and finished hedges. In recent years, increasing problems have been seen in the production of privet, partly in the propagation phase with significantly decreasing rooting percentages at some producers and partly in the growth phase, where significantly increased flowering is experienced in privet plants with special challenges in finished hedge production, which results in significantly lower growth and negatively affects shape formation. The strong flowering also affects further growth as a hedge among consumers, who may experience less success with privet hedges in general. These changes are seen to a particularly high degree in the Ligustrum ’Liga’ variety, which is the main variety on the Danish market, but also to a certain extent in other privet varieties.
The reason for these changes is not known, but one of the hypotheses is that the variety material exhibits ‘aging’, i.e. that the material used is transitioning from a juvenile form (juvenile, vegetative stage) characterized by good rooting and no flowering, to instead becoming a more adult form (adult, generative stage) that exhibits poorer rooting ability and begins flowering earlier after propagation. Aging of the mother material for the nursery area is known, among other things, from cutting hedges for e.g. Norway spruce, but is traditionally less known to cause problems for the hedge and ornamental shrub area. Climate change with more extreme weather, e.g. higher summer temperatures, can potentially also induce increased flowering, just as very hot or wet springs can potentially challenge the rooting of cuttings in the open field, which are used for privet.
There is therefore a need to investigate and understand what causes these changes and find solutions so that a high and safe rooting percentage can be ensured and heavy flowering can either be avoided or delayed and/or that adaptation of cultivation methods can ensure an acceptable growth both in production and among consumers.
