Abstract The cold requirement of Populus deltoides Bartr. in central Mississippi was investigated by forcing flower-bud-bearing branches collected in November, December, January, and February. Rapidity of flowering response increased from November to February. With the exception of material forced in January, leaving branches on trees for 30 days overcame cold requirements as effectively as storage at 4° C for that period. Tree-to-tree variation in flowering response was highly significant, as were all interactions involving individual tree effects. Male trees flowered earlier than female.