Anthropogenic climate change is causing demographic shifts at species' range edges. Trailing edge populations, which may be genetically distinct and adapted to relative climate extremes, already are showing declines in some species. The associated loss of trailing edge genetic diversity may limit possibilities for future climate‐adaptive restoration. For plants with recalcitrant seed, such as oaks, that cannot tolerate conventional seed banking, we propose a novel approach to the conservation of climate‐threatened genetic diversity: dispersed, participatory field gene banking. In this collaborative model, trailing edge transplants are stewarded at dispersed sites across a species' projected regional refugia. In 2018, we initiated a pilot participatory field gene bank for the foundational, endemic California blue oak (Quercus douglasii), a species experiencing increasing climate‐related declines at its trailing edge. To evaluate seedling performance, the gene bank was designed as a set of 23 small, dispersed common gardens with paired local and trailing edge seeds. Trailing edge seedlings showed lower survival and growth relative to locals, yet they also showed lower levels of leaf disease and herbivory, traits that could confer an adaptive advantage in a more xeric future. The substantial early survival of translocated seeds suggests that participatory field gene banking may offer an effective means of preserving trailing edge genetic diversity for oaks, thereby maintaining genetic resources that could be critical for future climate change‐adaptive restoration. However, further observations are needed to confirm the strategy's longer‐term viability and evaluate evidence of local adaptation.