Swamp White Oak – Quercus bicolor

Swamp White Oak – Quercus bicolor
Family Fagaceae – Beech, Chinkapin and Oak

This is a rapid-growing, long-lived tree of the north central and northeastern mixed forests.

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Swamp White Oak - Quercus bicolor
Throughout its range, swamp white oak is typically found on hydromorphic soils. These may be mineral soils that are imperfectly to poorly drained, as evidenced by high water tables and the presence of glei subsurface layers, or both; organic soils ranging from mucks (well decomposed) to peats (poorly decomposed) in which high water levels have favored organic accumulation; or alluvial soils underlain by a glei layer. These kinds of soils are associated with lands that are periodically inundated, such as broad stream valleys, low-lying fields, and the margins of lakes, ponds, or sloughs. Swamp white oak is not found where flooding is permanent.

It is found in lowlands, along edges of streams, and in swamps subject to flooding. It is rapid growing and long lived, reaching 350 years.

The tree is classed as intermediate in tolerance to shade, and seedlings become established under moderate shade. Lowland forests in which swamp white oak grows are characterized by instability and successional uncertainty because of the variable effects of flooding, together with the presence of saturated soils. Swamp white oak may achieve dominance on the better drained lowland soils together with basswood, northern red oak (Quercus rubra), American beech (Fagus grandifolia), and sugar maple (Acer saccharum). Once established, it is able to compete effectively with American elm, green ash, and black willow. Limited current evidence indicates clearcutting to be an adequate silvicultural system, particularly on the better sites. In forest stands swamp white oak has a straight bole with ascending branches and a narrow crown. However, open-grown trees are generally poorly formed and often have persistent lower branches.

This swamp white oak is approximately 40 years old.
Several insects attack oak trees. They are usually not important but may become epidemic and kill weakened trees. Economically, the most important are the wood borers. These may damage the wood of standing trees and cause log and lumber defects. White oak is attacked by several leaf eaters including the gypsy moth (Lymantria dispar), orange-striped oakworm (Anisota senatoria), variable oakleaf caterpillar (Heterocampa manteo), several oak leaf tiers and walking stick.

The Cynipid wasps cause galls to develop on the leaves, in the acorn or on the cup. White oak also hosts various scale insects, gall-forming insects, and twig pruners, but most of these are of minor importance. White oak acorns are commonly attacked by insects, in some cases affecting half the total acorn crop. Weevils of the genera Curculio and Conotrachelus cause most acorn damage. Light acorn crops usually are more heavily infested than heavy ones. Two moths damage acorns, the filbert worm (Melissopus latiferreanus) and Valentinia glandulella.

swamp white oak bark

The acorns are sweet, like others in the white oak group, and are eaten by squirrels and other rodents. In a study in Wisconsin, swamp white oak acorns were found to make up 27 percent of the diet of wild ducks. Several nongame bird species include these acorns in their diet.

swamp white oak foliage

Since the early 1990s, oak and tanoak (Lithocarpus densiflorus) have been dying in the coastal counties of California [1]. Since then, Phytophthora ramorum has been expanding its range in coastal California, killing millions of trees. This epidemic has caused damage to public and private property, economic impact on nursery, gardening and logging industries, and increased the cost of implementing regulatory activities. Many are worried that large-scale tree mortality will have profound long-term environmental consequences, by changing the structure of plant and microbial communities, altering landscape ecological structure and function, and increasing forest-fire hazards.

Phytophthora ramorum is known to infect over one hundred species of forest shrubs and trees. On oak and tanoak trees, P. ramorum causes bleeding bole cankers that can lead to relatively rapid mortality; hence sudden oak death. Other hosts such as California bay laurel (Umbellularia californica) suffer mild leaf-blight or twig-dieback symptoms and are major sources of inoculum for infection of oaks and tanoaks. There is no evidence for sporulation of this pathogen from true oak species [2].

A recent collaboration of scientists from all over the world published a study [2] of the spread of invasives, using Phytophthora ramorum to illustrate how shortfalls in their understanding of how cryptic infection spread can render management applications inappropriate.

 The risk of spread is enhanced by the pathogen's generalist nature and survival. Additionally, the extent of cryptic infection is unknown due to limited surveying resources and access to private land. The scientists used epidemiological modeling to estimate dispersal and life-cycle parameters of P. ramorum and forecast the distribution of infection and speed of the epidemic front in Humboldt County [2].


  1. USDA, APHIS, “Phytophthora ramorum/Sudden Oak Death”
  2. Filipe JAN , Cobb RC , Meentemeyer RK , Lee CA , Valachovic YS , et al. 2012 "Landscape Epidemiology
    Control of Pathogens with Long-Distance Dispersal: Sudden Oak Death in Northern Californian Forests."

    PLoS Comput Biol 8(1): e1002328. doi:10.1371/journal.pcbi.1002328

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Family Fagaceae – Beech, Chinkapin and Oak
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