On alluvial soils, the feeder roots are concentrated in the aerated layer above the saturated zone. Willow oak is monoecious. Acorn production begins when the tree is about 20 years old. This species produces a good acorn crop nearly every year. Blue jays transport and cache acorns up to several kilometers from the collection tree.
Germination is hypogeal.
Early height growth of seedlings is moderate. Moisture must be available during the entire growing season for best growth. However, complete soil saturation during the growing season inhibits root growth. Willow oak grows primarily on floodplain sites that are commonly flooded in the winter and spring, but only briefly during the growing season. This species usually grows on ridges and high flats of first bottoms which are the areas surrounding swamps and major rivers which flood deeply and frequently, but drain rapidly because of relief.