The differential ability of forest herbs to colonize secondary forests on former agricultural land is generally attributed to different rates of dispersal. After propagule arrival, however, establishing individuals still have to cope with abiotic soil legacies from former agricultural land use. We focussed on the plastic responses of forest herbs to increased phosphorus availability, as phosphorus is commonly found to be persistently bioavailable in post-agricultural forest soils. In a pot experiment under field conditions, we applied three P levels to four forest herbs with contrasting colonization capacities: Anemone nemorosa, Primula elatior, Circaea lutetiana and Geum urbanum. To test interactions with light availability, half of the replicas were covered with shade cloths. After two growing seasons, we measured aboveground P uptake, vegetative and regenerative performance. We hypothesized that fast-colonizing species respond the most opportunistically to increased P availability and that a low light availability can mask the effects of P on performance. All species showed a significant increase in P uptake in the aboveground biomass. The P addition had a positive effect on the vegetative performance of two of the species, which was, however, unrelated to their colonization capacities. The regenerative performance was affected by light availability (not by P addition) and was related to the species' phenology. Forest herbs can obviously benefit from the increased P availabilities in post-agricultural forests, but not all species respond in the same way. Such differential patterns of plasticity may be important in community dynamics as they affect the interactions among species.