We investigated springtime atmospheric particle formation in a Finnish boreal forest with respect to the spring recovery of photosynthetic capacity by using particle size distribution data together with a temperature-dependent state of photosynthetically active substances parameter, S. Spring is a period of exceptionally high particle formation event frequency and the events also produce a high number of aerosol particles. We found that the onset of the period of a high particle formation event frequency coincides with start of the spring recovery of the photosynthetic activity in the boreal coniferous forest. The highest particle formation frequency was found to occur with values of S close to 0 deg.C, which corresponds to a relative photosynthetic efficiency of about 30% of the maximum efficiency. The nucleation mode particle number concentration was highest with values of S between –3 deg.C and 0 deg.C, higher S resulting in lower average particle number concentrations. The increase in particle formation efficiency was also clearly reflected in the particle size distribution. Investigations in other atmospheric parameters important for nucleation revealed elevated ozone concentrations, but no clear other reason for the elevated particle formation activity. Therefore, we suggest that the particle formation peak is caused by biogenic volatile compound emissions from the boreal ecosystem that is undergoing spring recovery.