Red Oak

Red Oak Quercus rubraRed oak (Quercus rubra) is a member of the broad red oak group (black, blackjack, pin, northern pin, and shingle). This group is characterized by having bristles or points on the leaf lobes and acorns which mature in two growing seasons and sprout in the spring after maturity. Red oak leaves are simple and arranged alternately on the twig. They are 7 to 11 lobed, and 5 to 9 inches long with slender petioles 1 to 2 inches long. The lobes are usually no longer than one third the total leaf width; the sinuses of the lobes are u-shaped and the tips of the lobes are bristle tipped. 

red oak tree
Red Oak Tree - Photo by Paul Wray, Iowa State University 

Habitat: Found growing on moist upland woods. Rare in northwest 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 to 70 feet. Varies with species

Site Requirements: Best growth in moist, well-drained soils. Adaptable to adverse soil conditions.

Leaves: Alternate, simple, lobed. Lobes have pointed tips.

Flowering Dates: April - May

Seed Dispersal Dates: Late September - October

Seed Bearing Age: 25 years

Seed Bearing Frequency: Every 3 to 5 years

Seed Stratification: Prechill for 1 month at 34°F to 40°F

red oak leaf
Red Oak Leaf - Photo by Paul Wray, Iowa State University

The upper surface of the leaves are dull green while the lower surface is paler and without hairs except in the axils of the larger veins. Twigs are stout, reddish to greenish brown and without hairs. Winter buds are clustered at the ends of twigs, oval in shape with a sharp point, and usually chestnut brown in color. The bark on mature trees is brown to nearly black and broken up into wide, flat-topped gray ridges. On very old trees the bark may be deeply ridged and furrowed. 

Red oak is native to all of Iowa, except the northwest corner, although it is relatively rare in the northwest portion of its native range. Red oak occurs on a wide variety of sites ranging from stream terraces to dry ridges; but it is most frequently found on moist, well-drained slopes. It prefers soils which are moist, yet well drained and slightly acidic. 

Its common associates on the better sites include hard maple, basswood, bitternut hickory, black walnut, elms, and ashes. On drier sites, it often occurs with white oak and shagbark hickory. As with most of the oak species, red oak is moderately intolerant to shade. As a result, most successful oak seedlings are usually found in areas which receive full sunlight during part of the day.

Red oak grows moderately fast, sometimes maintaining a rate of 2 feet per year especially when young. Red oak commonly attains heights of 70-80 feet and diameters of 2-3 feet. Fall color is variable and ranges from red, orange red to deep reddish brown. 

Red oak is one of the best native oaks for landscaping because of its fast growth rate and its wide adaptability of sites. It is a much better oak for landscaping than the pin oak because of pin oak's susceptibility to iron chlorosis. In addition, it is more reliable for fall color development. 

The wood of red oak is hard, strong, and heavy like that of other oaks, but is less durable although easier to machine than white oak. Current demand for red oak lumber and veneer is high because of its increased use in both the furniture and housing industries. Other uses include pallet lumber, railroad ties, and firewood.

red oak acorns
Red Oak Fruit - Photo by Paul Wray, Iowa State University

Diseases that Can Affect Red Oak

Insects that Can Affect Red Oak

red oak twigs
Red Oak Twigs - Photo by Paul Wray, Iowa State University

red oak trunk showing bark
Red Oak Bark - Photo by Paul Wray, Iowa State University

young and mature red oak flowers
Red Oak Flowers - Photos by Paul Wray, Iowa State University