The identification and cloning of full-length homologs of circadian clock genes from Picea abies represent a first step to study the function and evolution of the circadian clock in gymnosperms. Phylogenetic analyses suggest that the sequences of key circadian clock genes are conserved between angiosperms and gymnosperms though fewer homologous copies were found for most gene families in P. abies. We detected diurnal cycling of circadian clock genes in P. abies using quantitative RT-PCR; however, cycling appeared to be rapidly dampened under free-running conditions. Given the unexpected absence of transcriptional cycling during constant conditions we employed a complementary method to assay circadian rhythmic outputs and measured delayed fluorescence in seedlings of Norway spruce. None of the two approaches to study circadian rhythms in Norway spruce could detect robust ~24h cycling behaviour under constant conditions. These data suggest gene conservation but fundamental differences in clock function between gymnosperms and other plant taxa.