This paper presents the draft assembly of the 20-gigabase genome of Norway spruce (Picea abies), the first available for any gymnosperm. The genome contains 28,354 well-supported genes, similar to the much smaller genome of Arabidopsis thaliana. There is no evidence of a recent whole-genome duplication in the gymnosperm lineage, suggesting that the large genome size results from the slow accumulation of diverse long-terminal repeat transposable elements. Comparative sequencing of other conifers reveals shared transposable element diversity. The study also identifies numerous long introns, gene-like fragments, uncharacterized long non-coding RNAs, and short RNAs, providing new insights into conifer genome evolution and potential avenues for forestry and breeding. The findings highlight the unique evolutionary processes that have driven the expansion of conifer genomes, which may have limited their morphological diversity but allowed them to dominate many ecosystems.This paper presents the draft assembly of the 20-gigabase genome of Norway spruce (Picea abies), the first available for any gymnosperm. The genome contains 28,354 well-supported genes, similar to the much smaller genome of Arabidopsis thaliana. There is no evidence of a recent whole-genome duplication in the gymnosperm lineage, suggesting that the large genome size results from the slow accumulation of diverse long-terminal repeat transposable elements. Comparative sequencing of other conifers reveals shared transposable element diversity. The study also identifies numerous long introns, gene-like fragments, uncharacterized long non-coding RNAs, and short RNAs, providing new insights into conifer genome evolution and potential avenues for forestry and breeding. The findings highlight the unique evolutionary processes that have driven the expansion of conifer genomes, which may have limited their morphological diversity but allowed them to dominate many ecosystems.