White Oak is a very large native deciduous tree, growing 80 to 100 feet in height and 3 to 4 feet in diameter, with wide-spreading mostly horizontal branches and a rounded crown.
Bark is light gray, scaly on smaller stems and shallowly fissured into irregular blocky plates on older trunks. These plates can meld together into somewhat smooth patches on large trunks.
Twigs are reddish-brown to gray, smooth, often shiny. There will be multiple small rounded terminal buds, also reddish-brown, without hair on the scales.
Leaves alternate, simple, oblong to ovate in shape, 4 to 7 inches long with a base that is a narrow wedge shape to triangular with the point forming the short stalk. There will be 7 to 10 (5 to 9) ascending lobes looking like fingers, and a rounded apex at the top end of the leaf. The lateral lobes indent to the mid-vein by 1/3 to 7/8ths of the distance and have a rounded sinus. The tips of some lobes may develop a few indentations forming rounded teeth. The upper surface is a bright gray-green and underside is more whitish with erect hairs that disappear as the leaf matures. The secondary leaf veins are arched. Fall color can be yellow to yellowish-red to mulberry which Eloise Butler referred to when she wrote: "The white oaks lend a distinctive tint of a peculiarly rich mulberry red" [Note 1]. Leaves from the juvenile part of the tree can resemble those of Swamp White Oak and Bur Oak.
Flowers: The tree is monoecious, that is with separate male and female flowers. Male flowers are a yellow-green, appearing in slender catkins, 2 to 4 inches long at the ends of the prior years growth. Each male flower has six stamens (can very from 2 to 12), which have long spreading white filaments when the flower fully opens. The female flowers are more reddish-green and appear as small slender spikes in the axils of new growth. The styles are slender and short. Both appear with the leaves.
Seed: The female flowers mature to an ovoid to oblong acorn, 3/4 to 1 inch long, at least 1/4 enclosed in a warty cap (this is highly variable as to cap coverage and acorn size by geographic location) with tight scales that have appressed grayish hairs. They usually appear in groups of 1 to 3 (generally in pairs) on a short stalk. The acorn matures in late summer into autumn of the first year as do most species in Quercus Sect. Quercus - the White Oak Group. They usually drop off the cup at maturity. The nut is light brown and can germinate immediately on falling from the tree. Dispersion is by animals. Trees require some age before bearing - upwards of 20 years.
Habitat: White Oak grows best in moist well drained soils, uplands and lowlands, but adapts to heavier soils. It grows slowly and is long-lived. The root system is a deep taproot and spreading lateral roots and will vigorously sprout from a stump. White Oak is very sensitive to soil compaction in the root zone. It is a highly variable species and will hybridize with Swamp White Oak and Bur Oak.
Names: The genus name, Quercus, is the Latin word for Oak. The species, alba, means white and refers to the color of the inner bark. The author name for the plant classification, 'L.' is for Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy.
Comparisons: The oak whose leaves is closest to White Oak is the Bur Oak, but with Bur Oak, not all the lobes are deeply cleft and usually only one pair is. Also the acorns of White Oak do not have the elongated fringe at the top of the cup like those of the Bur Oak acorns. Swamp White Oak Q. bicolor, is also similar. Check the Oak Leaf Comparison Sheet.
Above: Two views of the old white oak on the hill in the Upland Garden of Eloise Butler. Trees always show their structure better when bare.
Below: 1st photo - The bark on this tree shows the typical fissures of old bark and the flat plates that can occur on White Oak. Note same in 2nd photo which shows the White Oak that is a Minneapolis Heritage Tree in Eloise Butler with former Gardener Cary George who was responsible for registering the tree. 3rd photo - Twigs have multiple small rounded terminal buds, reddish-brown like the twig itself, without hair on the scales.
Below: 1st & 2nd photos - Additional various forms of White Oaks.
Below: Oak leaves can be variable in shape within a species. These examples show the triangular to wedge-shape base, the ascending lobes looking like fingers with rounded tips, and a rounded apex at the top end of the leaf. The lobes indent to the mid-vein by 1/3 to 7/8ths of the distance with a rounded sinus. Note the arching secondary veins. Fall color can be yellow to yellowish-red. Leaves from the young part of the tree can resemble those of Swamp White Oak and Bur Oak.
Below: 1st photo - Female flowers on new growth. 2nd photo - Male flowers are a yellow-green, appearing in slender catkins, 2 to 4 inches long at the end of the prior years wood.
Below: Fully elongated male catkins with many of the flowers open with the six stamens fully extended.
Below: White Oak acorns (immature 1st photo) have tight scales with appressed grayish hairs. The warty cap of mature acorns (2nd photo) encloses at least 1/4 of the oblong acorn. (2nd photo ©Steven Hurst, USDA-NRCS Plants Database).
Below: Fall color can be yellow to yellowish-red to mulberry which Eloise Butler referred to when she wrote: "The white oaks lend a distinctive tint of a peculiarly rich mulberry red" [Note 1]. This does not occur every fall but when conditions are right, the tree can be beautiful as seen in the old specimen at Eloise Butler.
Notes: White Oak is indigenous to the Garden. Eloise Butler catalogued it on April 29, 1907. In North America it is found in the eastern half of the continent, from Minnesota to Texas and eastward to the coast. In Canada it is known in Ontario, Quebec and P E Island. Minnesota is at the NW corner of the tree's range so in Minnesota the range is restricted to mostly the SE quadrant east of a diagonal line from Mower to Stearns counties and then to Crow Wing and eastward to Pine. There are a few scattered exceptions.
Note 1: Quote taken from Effective Coloring in the Wild Garden That is not due to Flowers, Dec. 1915, unpublished.
Native Oaks: The current native oaks in Minnesota are 6: Q. alba, White Oak; Q. bicolor, Swamp White Oak; Q. ellipsoidalis, Northern Pin Oak; Q. macrocarpa, Bur Oak; Q. rubra, Northern Red Oak; Q. velutina, Black Oak. One other is historical - Q. muhlenbergii, Chestnut Oak, known only from Houston County and last collected in 1899. Several hybrids are historically known. Several others grow well here under certain conditions such as Q. palustris, Pin Oak; and Q. coccinea, Scarlet Oak.
Uses: White Oak is a heavy, hard, strong wood and its our best source of fine wood for lumber, paneling, furniture, cabinetry, barrels and in former times for shipbuilding. It has been logged so intensively and grows so slowly, that except for liquor barrels, Red Oak has substituted for a lot of the former uses. The acorns are edible although bitter and with some tannin. Bitterness is removed by leaching and the tannin by boiling. Native Americans made use of most acorns for acorn-flour. Fernald (Ref. #6) has some detail on how this was done.
It is not too difficult to visually identify a piece of oak lumber as White Oak but more difficult to separate it from the other members of the White Oak group. There are clear contrasts with the Red Oak group. In the White Oaks the tallest of the largest rays are greater than 1-1/4 inches and the latewood has numerous small pores that grade into invisibilty, whereas the Red Oak group has the tallest rays less than 1 inch and the latewood pores are few and more distinct. A small hand lens is necessary to see this clearly.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"