Swamp White Oak

Quercus bicolor

Description & Overview

Oak genetics are amazingly diverse and there seems to be an oak tree adapted for almost every situation. This is a striking large tree with attractive peeling bark and a great choice for a shade or street tree.

Core Characteristics

Suggested Uses:

Swamp White Oak is a key component of forested wetlands. It shares the same niche as Pin Oak and Swamp Chestnut Oak, which you’ll find in the Southern and Eastern parts of North America. It’s one of the best hardwoods for wet soils. As the name suggests, this oak is adapted to moist sites like swamps and river edges. Some wet sites are associated with thick layers of clay and the modern Swamp White Oak has evolved a root system capable of dealing with these compacted soils.

The open rounded crown makes it an excellent shade tree for large lawns, golf courses, parks, and naturalized areas. This Oak prefers rich, moist to wet soils that are slightly acidic. It has also proven to be adaptable to dry, average soils that are neutral to slightly alkaline in pH. This is a large, long-living tree, so be careful when selecting a site to ensure it has plenty of room to live its best life.

Wildlife Value:

Your wildlife can benefit from the Swamp White Oak! The acorns are a favorite among birds, such as woodpeckers, wild turkeys, and blue jays. Small mammals, white-tailed deer, and black bears also use them as a food source. A heavy acorn crop is produced every 3-5 years drawing in local wildlife for a tasty autumn snack. The caterpillars of Hairstreak butterflies, Duskywing skippers and numerous moths feed on the foliage and other parts of the tree. Other insect feeders include several leaf beetles, Miridae, and the larvae of various gall wasps. These various insects are an attractive source of food for warblers, flycatchers, and other insectivorous birds. In addition to being a vital food source for a plethora of wildlife, the Swamp White Oak also provides cover or a humble abode for many birds and small mammals in its broad, open canopy.

Maintenance Tips:

Young Swamp White Oaks are tolerant of light shade but prefer full sun. It has a surprisingly high resistance to both drought and compaction, meaning you’ll find it in a variety of soils and locations. However, it’s intolerable of high alkalinity and may become chlorotic if planted in a site with high alkaline soils. This oak also has a resistance to the allelopathic effects of Black Walnut toxicity; this makes it easier to find a suitable planting location. It’s also considerably easier to transplant thanks to its fibrous root system.

We recommended pruning during the winter when the tree is dormant. Pruning from April to the first hard freeze can expose the tree to oak wilt. Oak Wilt is a fungal disease that can prove fatal to Oak trees of any age if left untreated. You can learn more about Oak Wilt and how to treat it in the Pests and Problems section below.

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.

We have a pair a beautiful Swamp White Oak outside our offices that display an awesome central leader system in winter.

Pests/Problems:

A healthy, stress-free Swamp White Oak has few significant insect or disease problems. Taking measures to avoid damaging or wounding the tree during the growing season will prevent Oak Wilt infection.

Oak wilt is a fungal disease that invades areas inside the tree where water moves. Once infected, balloon-like bumps called tyloses are formed and these bumps plug the waters path throughout the tree. As the water movement is slowed the leaves eventually wilt and drop. Oak Wilt can spread above ground by sap-feeding beetles or underground by interconnected root grafts from infected oaks to healthy oaks. The best treatment is prevention, however if your oak contracts this infection we recommend a trunk injection of a systemic fungicide such as Popizol.

The Two-Lined chestnut borer is a pest that targets all Oak species. They are susceptible during the establishment period after planting. Applying a systemic insecticide that contains imidacloprid when planting is a good way to protect your tree. We recommend treating B&B oaks for the first two years after planting. The best defense against the Two-Lined Chestnut borer and other common ornamental problems like anthracnose or leaf spot is prevention. Healthy, non-stressed trees won’t attract these pests and diseases.

Swamp White Oaks are sensitive to Iron chlorosis and should not be planted in soils with high alkalinity. If you are working in high alkaline soil conditions and want to use Swamp White Oak, consider switching your specification to the more alkaline adaptable Hybrid Swamp x Bur Oak.

Leaf Lore:

Quercus bicolor is part of the Beech (Fagaceae) Family. The specific epithet bicolor refers to the leaves being shiny green above and silvery white beneath. This tree was awarded the Society of Municipal Arborist’s 1998 Urban Tree of the Year and was chosen to be the single species to fill over 400 planting locations at the National September 11th Memorial in Manhattan, New York.

The world’s oldest Swamp White Oak still standing to this day is approximately 220-260 years old with a whopping 21” caliper and standing at approximately 90-feet tall. This old timer is in Nashville, TN.

Oak Galls and Parasitic Wasps have a fascinating relationship. When certain wasps lay their eggs on Oak trees, the larva produces a hormone that causes the tree to produce a gall. A gall is an irregular growth that encapsulates the larva and protects it from the elements, predators, and parasites. Galls produce a nectar that attract ants and other wasps, who in turn help protect the oak from herbivores such as caterpillars. Interestingly, certain parasitic wasps will bore into oak galls and lay their eggs inside to feed on the helpless gall wasp larva. Yet there are also other wasp species that are known to parasitize the parasitic wasp that takes over the gall, making them hyper parasites! Up to five levels of parasitism are possible in oak galls, the largest parasitic hierarchy known to occur in nature.

Companion Plants:

In a forested ecosystem, Swamp White Oak can be seen near other natives such as Sugar Maple, American Beech, or other Oak species as well with common understory plants such as Smooth Sumac or Pagoda Dogwood. In more wet sites, common neighbors include Silky Dogwood, Harlequin Blue Flag Iris, Joe-Pye Weed, Musclewood, River Birch, or Glossy Black Chokeberry.

SWAMP WHITE OAK BENCHCARD