c4c89 white oak habit
White Oak Tree

The White Oak tree is an outstanding, native tree with a natural range that spreads across eastern North America and into southern Ontario and Quebec, Canada. The White Oak is hardy in USDA Zones 3 through 9. It’s a long living tree with some specimens documented to exceed 450 years old. Although called the “White Oak”, it is actually very unusual to find an individual specimen with white bark. Ordinarily, the bark color is light gray. When growing in the open, the White Oak tree develops into a massive, broad topped tree with large branches striking out at wide angles. In the forest, the tree can reach a magnificent height. The tallest known White Oak is 144 feet tall.

The White Oak tree possesses many lovely characteristics. In spring the young leaves are a delicate silvery-pink color and are covered with a soft, blanket-like down. The petioles are short, and the leaves which cluster close to the ends of the shoots are pale green and downy, giving the whole tree a misty, frosty look. This appearance continues for several days, passing through opalescent changes of soft pink, silvery white and finally yellow-green. In the summer, leaves grow to be 5 to 8 inches long and 3 to 4 inches wide, with a deep glossy-green upper surface. In autumn the leaves usually turn a red or brownish-red color. Other notable members of the “White Oak group” are Bur Oak, Swamp White Oak and Post Oak. Depending on individual genetics, some White Oak trees are red, brown or even purple in autumn. If a certain fall color is your penchant, it’s advisable to observe the prospective tree in the nursery at autumn time to check its’ color. Oftentimes, some leaves may remain on the White Oak tree through the winter until they are dropped in early spring. This trait appears more often in younger Oak species, including the White Oak. In native stands the smaller, younger Oak trees will stand out in winter from the bare mature specimens due to their leaf retention. I personally like this “winter interest” characteristic when everything else is bare. But some complain it causes more leaf raking. While I admit that’s true, I think it is worth it. The White Oak tree leaf shape is either lobed with shallow or deep indentations. The tree acorns grow from a ½ inch to one inch in length and fall from the tree in late September to early October. The acorns germinate immediately in the autumn, if there has been suitable moisture, such as after rainfall. Germination is “hypogeal”, meaning the root grows first while the shoot remains dormant. Root growth continues until it’s interrupted by cold weather. Both root growth and shoot growth commence again in the spring. First season shoot growth is typically three to four inches high, but the developing taproot can be up to 12 inches long.

White Oak trees grow and flourish in a wide range of soils and sites. Soils that are sandy, gravelly, loam or clay loam are just fine for the White Oak. It also enjoys a wide range of tolerable pH levels, from 3.7 to 7.3. Good soil drainage is very important for the White Oak tree, but it is tolerant of salt spray and brief salt water submergence of the root zone. Although mostly urban tolerant, the White Oak tree does have a reputation of soil compaction intolerance and soil additions over the root zone. My personal observations of this is when forest or meadow grown mature trees are exposed to foot or equipment compaction in the root zone, or if there is soil added to the same area. This may cause the tree to enter a downward spiral. However, young White Oaks planted in compacted soils will exist in parkways, lawns and parks and appear to adapt to the soil conditions, although they may experience a slower rate of growth. When planting, it’s vital that the White Oak tree receives full to part sun exposure. Once established, the White Oak tree is very drought tolerant. This tree makes an outstanding shade tree in the landscape.

Overall, the White Oak tree is generally a healthy, long-lived tree. However, it is susceptible to minor cosmetic injury of its leaves and twigs due to chewing insects, gall producers and some fungi. One fungus in particular is Oak Wilt, but the White Oak tree is less susceptible than trees in the “Red Oak group” of Oaks. The White Oak may lose only a limb at a time, or may harbor Oak Wilt infection without ever showing symptoms. Wounding of Oaks should never occur during the growing season (April 15th through late October) due to the greatly increased susceptibility to the Oak Wilt fungus. White Oaks growing or planted in stands of other Oaks within fifty feet of each other should be closely monitored for Oak Wilt infection or for any other pathogen.

In general, the White Oak tree successfully performs in both cultivated and natural landscapes. This has been especially evident in the latter, but the White Oak has been vastly underutilized in the former. The White Oak tree is best transplanted as a smaller tree, due to its’ tap root system. In addition, the White Oak should be transplanted in early spring only.  My experience with this species is that fall digging and planting results in a dead Oak tree the following spring.  This trait is related to the particular physiology of Oaks. The White Oak is much less commonly available than its deservingly popular cousin, the Swamp White Oak (Quercus bicolor). However, it can be found if asked for at local nurseries. This tree has so many outstanding attributes it has been named the state tree of Connecticut, Maryland and Illinois. The White Oak tree is one of the pre-eminent hardwoods of eastern North America. Its’ wood is highly valued as premium lumber all over the world. It is highly adaptable to many environments across its’ wide geographical range. The White Oak tree deserves a much larger representation in the landscape and should be given a revered position in our “diversified urban tree species planting list”.

 

Harold Hoover
Kramer Tree Specialists
Board Certified Master Arborist  IL-1478B
 

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