While the influence of elevated CO 2 on the production, mass and quality of plant seeds has been well studied, the effect of warming on these characters is largely unknown; and there is practically no information on possible interactions between warming and elevated CO 2 , despite the importance of these characters in population maintenance and recovery. Here, we present the impacts of elevated CO 2 and warming, both in isolation and combination, on seed production, mass, quality, germination success and subsequent seedling growth of Austrodanthonia caespitosa, a dominant temperate C 3 grass from Australia, using seeds collected from the TasFACE experiment. Mean seed production and mass were not significantly affected by either elevated CO 2 or warming, but elevated CO 2 more than doubled the proportion of very light, inviable seeds (Po0.05) and halved mean seed N concentration (Po0.04) and N content (Po0.03). The dependence of seed germination success on seed mass was affected by an elevated CO 2 Â warming interaction (Po0.004), such that maternal exposure to elevated CO 2 or warming reduced germination if applied in isolation, but not when applied in combination. Maternal effects were retained when seedlings were grown in a common environment for 6 weeks, with seedlings descended from warmed plants 20% smaller (Po0.008) with a higher root : shoot ratio (Po0.001) than those from unwarmed plants. Given that both elevated CO 2 and warming reduced seed mass, quality, germinability or seedling growth, it is likely that global change will reduce population growth or distribution of this dominant species.