From Halopedia, the Halo wiki
The tree species Quercus alba, also called white oak, is a type of oak tree and one of the most common hardwoods of eastern North America. It is a long-lived oak in the family Fagaceae, native to eastern North America, from southern Quebec west to eastern Minnesota, and south to northern Florida and eastern Texas. Specimens are known to have lived over 600 years.
Although called the white oak it is very unusual to find an individual with white bark; the usual color is an ashen gray. In the forest it reaches a magnificent height. In the open it develops into a massive broad-topped tree with great limbs striking out at wide angles.