Geographic variation in Quercus rubra in north central United States plantations.
Trees from 31 sources were grown in seven localities and the variation observed in 14-year-old trees was recorded. Time of flushing and of autumnal change in leaf colour appeared to be under strong genetic control and showed well-defined geographic variation. Trees from the north central region flushed the earliest, and early autumn leaf-colour change was associated with high latitude. Trees from regions subject to summer drought were the most drought resistant. Growth rate varied with seed source but family and stand differences were more important.