Swamp white oak (Quercus bicolor) is a member of the broad white oak group (white, bur, chinkapin, swamp white, and post oaks). This group is characterized by having rounded lobes on the leaves and acorns which mature in a single growing season and sprout soon after they fall in the autumn.
Habitat: Grows in bottomland areas of eastern one-third of Iowa.
Hardiness: Varies with the species of oak tree, ranging from zone 3 to zone 9
Growth Rate: Slow to Moderate
Mature Shape: Broad, rounded
Height: Varies with species. Often maturing between 50 to 75 feet tall. Capable of growing upwards of 100 feet.
Width: 40-70 feet; varies with species
Site Requirements: Best growth in moist, well-drained soils. Adaptable to adverse soil conditions.
Leaves: Alternate, simple, lobed; lobes with rounded tips
Flowering Dates: Mid spring
Seed Dispersal Dates: October
Seed Bearing Age: 20 years
Seed Bearing Frequency: Every 3 to 5 years
Seed Stratification: Prechill for 4 months at 34°F to 40°F
Swamp white oak is native to eastern Iowa; as far west as the Wapsipinicon River, the Iowa River and streams in Decatur and Taylor counties in southern Iowa. As the name implies, it is found in low-lying moist sites, along bottomlands and in swamps subject to periodic flooding; its common associates include most bottomland species such as silver maple, hackberry, American elm, green ash, black walnut, shingle and pin oaks, and river birch. It grows faster than most other white oaks, attaining a height of 60 to 70 feet and a trunk diameter of 2 to 3 feet. It is long lived like most oaks, attaining ages of 300 years or more.
The leaves are large (5 to 7 inches long) with rounded, shallow lobes. They are dark green above and gray to shiny white and downy below. The botanical name of swamp white oak means "two color" referring to the strong contrast in color between the upper and lower surfaces of the leaf. The twigs are green and lustrous, becoming light orange colored or brown by the first winter.
The bark is smooth on small branches, purplish brown and separates into large, papery scales. On large branches and trunks, the break breaks into broad, flat ridges, with deep fissures and is gray-brown to reddish brown in color. The acorns (3/4 to 1-1/4 inches long) usually occur in pairs on a very long stalk, 1 to 4 inches long.
The wood of swamp white oak resembles that of other white oaks; it is heavy, hard and moderately durable. Because the tree retains its lower branches, the wood is usually less valuable than other white oaks; in addition its relative scarcity makes it of less importance than other native oaks as a timber tree. Its bottom land location makes it valuable as a source of food for wood ducks, deer, turkey, squirrels and other rodents.
Swamp white oak makes an excellent shade tree when planted on the right soils. It like many other bottomland species has a relatively high requirement for iron. Avoid planting swamp white oak on calcareous soils; it prefers acidic, moist to wet soils for optimum growth and development. Its fall color is less than spectacular; fall color is usually brown.