A monarch of our climax forests in Wisconsin! Red Oak shines as a specimen tree with its brilliant red fall color and deep green leaves in summer. It is the fastest growing native oak in Wisconsin and its silvery smooth bark provides excellent winter interest when young. Do not prune in spring, summer, or fall to prevent Oak Wilt. May also be known as Northern Red Oak, Gray Oak.
Wisconsin Native: Yes
USDA Hardiness Zone: to zone 3
Mature Height: 60-75 feet
Mature Spread: 60-75 feet
Growth Rate: Moderate
Growth Form: Tree, rounded, broad
Light Requirements: Full Sun
Site Requirements: Prefers rich, acidic, well drained organic soils, tolerates urban pollution
Flower: Monoecious, insignificant male and female flowers emerge in spring with leaves
Bloom Period: April-June; variable
Foliage: Dark Green
Fall Color: Russet Red to Bright Red
Urban Approved: Yes
Fruit Notes: Acorn, medium brown, 0.75-1 inch, small cap (involucre), good crops every 2-5 years
Waukesha, Milwaukee, and Washington Counties, WI
Red Oak is an excellent plant as a specimen or street tree as long as there is enough room for it at maturity. The outstanding fall color contrasts well with yellows and oranges. While the species may develop chlorosis on alkaline sites, we select our Red Oaks for their tolerance of soils with higher pH.
The acorns of Red Oak, like other members of the Red Oak Group, are higher in tannin content and more bitter tasting than those of the White Oak Group. However, Red Oak produces acorns more frequently and consistently than White Oak and is still an important food source for wildlife. Expect to see turkey, deer, squirrels, and other small mammals feeding on the acorns.
Woodpecker, blue jay, and tanager can be found in the canopy feeding on insects.
Red Oak is a larval host for the beautiful Gray Hairstreak
All oaks are susceptible to Two-Lined Chestnut Borer during the establishment period after planting. Apply a systemic insecticide containing imidacloprid to Red Oak when planting to protect the tree from this insect.
Do not prune Red Oak during the growing season. Red Oaks are highly susceptible to Oak Wilt which is spread by a sap beetle attracted to fresh wounds. Prune only during the dormant season in winter after the leaves have fallen. Oak Wilt can kill a Red Oak within one season if the tree is stressed, and is always fatal to trees in the Red Oak Group.
As a near-climax forest species in Wisconsin, Red Oak benefits from a maintained mulch ring at its base. This mimics the natural duff layer in a forest environment and protects the shallow roots from mechanical damage and drought.
The thin bark of Red Oak is susceptible to mechanical damage and deer scrape. Protect the trunk with a trunk guard during the winter months, and maintain a mulch ring at its base to prevent damage from lawn implements.
We invite you to check out the Arborist For Hire lookup at the Wisconsin Arborist Association website to find an ISA Certified Arborist near you.
Oak Wilt is the primary disease for Red Oak. In a forest setting, this fungus will spread through root grafts between trees and kill entire stands. In a landscape setting, however, Oak Wilt is easy to avoid. Red Oak should only be pruned during the dormant season when the sap beetle is not active. Unfortunately, Oak Wilt is always fatal to Red Oaks and cannot be treated once the tree is infected. Consult an arborist if you think your tree may be afflicted.
The most important care maintain health and vigor through good mulching and adequate watering. During the first two years after planting, make sure the tree has enough moisture to properly establish its roots. Use a systemic insecticide to protect it from Two-Lined Chestnut Borer.
If stressed, Bur Oak is susceptible to attack by Two-Lined Chestnut Borer, Armillaria Root Rot, Strumella and Nectria Canker, Anthracnose, Powdery Mildew, and Gypsy Moth. The best treatment for these problems is prevention by maintaining tree vigor through proper watering and mulching.
While our Red Oaks are selected for superior tolerance of alkaline soils, other Red Oaks may develop chlorosis (yellow leaves) on alkaline sites. Take care when selecting your plants and make sure that they tolerate alkaline soils, especially when planting in Southeast Wisconsin or urban areas.
When grown naturally, Oaks develop a coarse, deep root system with a taproot. This has made them historically difficult to transplant as balled-and-burlapped (B&B) trees because much of the root system is lost in the harvesting process. Our trees are unique because they are root pruned from the start to develop more fibrous fine roots. When harvested, our B&B oaks contain more fibrous roots, making them tougher and easier to transplant than oaks not given our unique treatment process.
Red Oak is the fastest growing native oak in Wisconsin, rivaled only by Hybrid Swamp x Bur Oak. It also sustains this rapid growth the longest of all the oaks, up to 3 feet per year when conditions are right.
Red Oak can hybridize with other members of the Red Oak Group, including Northern Pin Oak and Black Oak.
The thin bark of Red Oak is not adapted to fire, which restricts its range from prairies. It is considered an intermediate successional tree, able to establish beneath the canopy of Aspen and Red Maple but unable to regenerate in the shade favored by Sugar Maple and American Beech.
In our climax forests, Red Oak grows with American Beech and Sugar Maple, providing a spectacular show of fall color. Understory associates include Downy Serviceberry, Bladdernut, Ironwood, and Witch Hazel.