This publication presents measurements of sedimentary organic carbon stocks in the vegetated shorelines of boreal lakes, so called ‘teal carbon’ environments. The three large Finland lakes in this study show a large variability in teal carbon storage, with grain size as the most significant parameter explaining the variability. The amount of sedimentary organic carbon storage is related further to abiotic and biotic controls. Teal carbon is an important component of overall lacustrine carbon storage, and the process-based controls elucidated in this study may provide insight into carbon storage in other boreal lakes as well.