How Much Light for an Oak Tree?

Sunlight Requirements

• Most oak trees can tolerate some shade during their early growth but need full sunlight once they mature. Scarlet oak (Quercus coccinea), bur oak (Quercus macrocarpa), northern red oak (Quercus rubra), sawtooth oak (Quercus acutissima) and pin oak (Quercus palustris) all require full sunlight once established. Species tolerant of partial shade include white oak (Quercus alba), overcup oak (Quercus lyrata) and the evergreen live oak (Quercus virginiana). U.S. Department of Agriculture plant hardiness zones also vary by species. The white oak, found across a wide area of the continental United States, can be grown in USDA zones 3 to 9, while growth of the live oak is restricted to warmer USDA zones 7 to 10.

Reproduction

• All oak trees produce acorns, round-capped nuts that range in color from light green to brown. Each acorn is a complete and fertilized embryo that, given the right conditions including enough nutrients, water and bright direct or indirect sunlight, will produce a new oak tree. Acorns produced during the spring and summer are released toward the end of the season when their stems weaken. Most are blown down by the wind, but squirrels, raccoons and large birds such as crows also knock down their fair share during their search for food.

Germination

• The acorns of some species, such as the bur oak and white oak, germinate immediately after falling from the trees, while those of the northern pin oak and northern red do so the following spring. At germination, the acorn's outer casing splits open, releasing its two-part cotyledon and a long taproot. The cotyledons appear as two false leaves, while the root makes its way immediately into the soil. Acorns sprouting in the open away from other trees have the best chance of survival, as they are exposed to the maximum amount of sunlight. Oaks that sprout under a dense canopy of other types of trees often do not survive or develop poorly, producing long trunks and sparse tops that are forced to compete for the light.

Other Requirements

• Oak trees do best if planted at the lower levels of slightly sloping land that faces north or east. Soil should be at least 36 inches deep, rich and well-drained, as oaks do not tolerate standing water. Oaks can be grown from acorns harvested in the fall or introduced into the landscape as established seedlings obtained from a nursery, which considerable shortens the initial growing time. Acorns harvested later in the year, in October and November, are usually healthier and less likely to have been affected by worms. Refrigerated until spring, acorns are then ready to be planted in pots before being moved to their permanent homes in the early fall.