EXPERIMENTS FOR STIMULATION OF FLOWERING IN SEED ORCHARDS

The results of important experiments for flower stimulation, carried o ut by the working group of the Instituts for Forest Tree Breeding of t he federal states and by the formerly Department for Forest Tree Breed ing of the Institut for Forest Research Eberswalde in the seventies an d eighties are summariezed in this work. The applied methods could be devided in mechanical treatments (e. g. girdling, Strangulation, root pruning, thinning), applications of fertilizers and treatments with bi oregulators. In the hole 17 seed orchard (7 tree species) were treated . Mechanical treatments stimulated the flowering of the grafts often ( especially girdling and strangulation), but they are very labor-intens ive and not useable in a larger scale in practice. Only thinning is us eful practicable in commercial seed orchards. Fertilization (especiall y nitrogen) influenced the cone yield particulary in Scots pine seed o rchards on poor soils positively. The results of the experiments with bioregulators were very different and partly contrary. In addition to the choice of the suitable agent especially the time of application wa s important for a stimulation of flowering. The application of CCC in the second periode of May increased the number of female flowers in Sc ots pine and European larch. There is a need of further experiments fo r the stimulation of flowering in seed orchards by bioregulators. If t here is a lack of nutrients in the seed orchard, fertilization is advi sable.