In two saltmarshes, Old Hall in the Blackwater (southeast England) and Warton Bank in the Ribble (northwest England), we took vegetation and soil samples every six to eight weeks from March/April 2025 to September 2025 to characterise seasonal denitrification and vegetation dynamics. A key ecosystem service in coastal systems is the remediation of nutrient pollution through sediment burial, vegetative uptake and microbial processing. Denitrification is a facultative anaerobic process where microbial activity transforms nitrate (NO3-), which in high concentrations can be environmentally harmful, into the environmentally benign dinitrogen gas (N2). Denitrification's magnitude is considered particularly important in saltmarsh systems compared to other habitats, although an intermediate product, nitrous oxide (N2O), can also be given off and contribute to climate change. This dataset continues the timeline started in https://doi.org/10.5285/26efc506-a265-4bb1-8296-d6988ab8d714 Full details about this dataset can be found at https://doi.org/10.5285/fd918e24-4fd8-4e32-867a-b1a1fe74ce12