[This nonGeographicDataset is embargoed until March 11, 2026]. This dataset contains daily germination rates of temperate tree species’ seed under elevated ozone fumigation in a closed chamber system. Daily counts of germinated sees were made. The seeds were exposed to an ambient and +60 parts per billion ozone treatment for approximately one month in the winter of 2024. Species tested were Betula pendula, Pinus sylvestris and Picea sitchensis. These data were collected to examine the possible effect of ozone on timing and percentage success of seed germination. Full details about this nonGeographicDataset can be found at https://doi.org/10.5285/e0226c12-f07a-48a6-8bef-9ae9e0a7d249