Despite rapid warming, seed production is not leading poleward migration in North American and European forests. - Clark JS; Bankston T; Bogdziewicz M; Cailleret M; Camarero JJ; Delzon S; Fady B; Hacket-Pain A; Hanley ME; Hu M; Ibáñez I; Jenkins L; et al. (The New phytologist, 2026)