The results of phenological observations of the generative organs of Norway spruce (Picea abies [L.] Karst.) in the Zvolen Basin are analysed. Twenty autochthonous spruce populations taken from its natural areas of distribution and planted in the Arboretum of Borova Hora belonging to the Technical University of Zvolen present the altitudinal range of 500-1,450 m. The 10% beginnings of phenological stages as a Flower buds swelling, a Formation of flowers before blossom, flowering and blossom fall were observed during the period of 2006-2008. Flower buds swelling occurred on its average from 12th till 21st of April and lasted 9-11 days predominantly. The formation of flowers before blossom occurred from the 23rd of April till the 2nd of May and lasted 5-6 days. The stage of Flowering began on its average from 29th April till 8th May and predominantly lasted 5-6 days. Blossom fall occurred on average from 5th till 17th May and predominantly lasted 11-12 days. The earliest occurrence of phenological stages was recorded in years 2007 and 2008, while a moderate delay in the year of 2006 caused by low temperature and long lasting snow cover. Variation coefficients approached values from 0.57 up to 3.19%. The equalization of air temperature course during the later spring period resulted in the observed decrease of variability of both the Flowering and Blossom fall. The altitude of original sites, the observed provenances come from, has not influenced neither the time of particular phenological stages beginnings nor the lengths of their periods. The conditions of a new environment proved to be decisive.
