The influence of seed production on litterfall was studied for 2 years at five northern hardwood sites located across the Great Lakes region. Flower and seed litter contributed > 1 Mg/ha dry matter in several instances, accounting for as much as 34% of total litter deposition. Significant differences between years were measured for both foliar and reproductive litter inputs at the sites. Production of reproductive litter and foliar litter were negatively correlated at the stand level (r = 0.99, P < 0.001), suggesting a direct trade-off between leaf biomass and reproductive biomass. Bumper seed crops had a large impact on total aboveground N litterfall. Reproductive N flux was a high as 41 kg/ha/year. Averaged across both years and all sites, reproductive litter accounted for 36% of total N in aboveground litterfall (range = 14-61%). When compared with the amount of N returned in foliage, reproductive litter averaged 67% (range = 18-174%). Nitrogen uptake and return in litterfall can be underestimated, especially during periods of heavy seed production, if flowers and seeds are ignored. Periodic life-history events like seed production can play an important role in ecosystem-level processes like N cycling.