Bur oak (Quercus macrocarpa): what the agencies record

This page reports what US federal publications say about one tree. It does not identify trees from descriptions or photos and does not say what should be done with any tree. The family overview, tree species in the agency records, explains the sources and holds the comparison table.

At a glance

Item	What the source records
Scientific name	Quercus macrocarpa Michx. in USDA PLANTS, beech family
Other names	Blue oak, mossycup oak, mossy-overcup oak and scrub oak (Silvics)
Native status, USDA PLANTS	Native in Canada and the lower 48 states
Size, Silvics	On the better sites mature trees generally grow 24 to 30 m (80 to 100 ft) tall and 91 to 122 cm (36 to 48 in) in diameter at breast height and live 200 to 300 years; one tree in the lower Ohio Valley is said to have reached 52 m (170 ft) and 213 cm (84 in)
Acorns, Silvics	Described as having the largest acorns of all native oaks
Green weight of the wood, NRS-38	63 lb per cubic foot, without bark

Native range and sites

The Silvics of North America handbook (Agriculture Handbook 654, volume 2, 1990) says bur oak is widely distributed throughout the Eastern United States and the Great Plains. It ranges from southern New Brunswick, central Maine, Vermont and southern Quebec west through Ontario to southern Manitoba and extreme southeastern Saskatchewan, south to North Dakota, extreme southeastern Montana, northeastern Wyoming, South Dakota, central Nebraska, western Oklahoma and southeastern Texas, then northeast to Arkansas, central Tennessee, West Virginia, Maryland, Pennsylvania and Connecticut, and it also grows in Louisiana and Alabama.

The handbook says the tree grows slowly on dry uplands and sandy plains but is also found on fertile limestone soils and moist bottomlands in mixture with other hardwoods, and that in the west it is a pioneer tree invading prairie grasslands and is planted frequently in shelterbelts. It calls bur oak one of the most drought resistant of the North American oaks, with average annual precipitation as low as 380 mm (15 in) in the northwestern part of the range, and says it is a fine tree for streets or lawns because of the comparative ease with which it can be grown.

Flowers and growth

Silvics says bur oak is monoecious, flowering shortly after the leaves appear, from about the first of April in the southern part of the range to about mid-June in the north. It describes a slow-growing tree: in Iowa plantations 12 to 16 years old, average annual height growth ranged from 0.09 to 0.52 m (0.3 to 1.7 ft). Diameter growth over a 10-year span in Iowa averaged 3.0 cm (1.2 in) for trees 10 to 20 cm (4 to 8 in) across and 5.6 cm (2.2 in) for trees 56 cm (22 in) and larger. Mature trees characteristically have a massive, clear trunk and a broad, open crown of stout branches. In the oak openings of southern Wisconsin and the prairie border areas, the handbook says bur oak often forms nearly pure stands of widely spaced, short-boled trees, and that on dry limestone ridges trees may be less than 7.6 m (25 ft) tall at 150 years of age.

Roots

The handbook says taproot development continues to be rapid in the sapling stage, with abundant lateral growth: the taproots of 8-year-old saplings in upland clay soils of Missouri were more than 4.3 m (14 ft) long, and primary laterals extended up to 3.4 m (11 ft). In prairie areas, roots of bur oak and hackberry have been found at depths of 3 to 6 m (10 to 20 ft). In a study of a tree 36 cm (14 in) in diameter, the weight of the roots equaled that of the tops.

Varieties and hybrids

Silvics recognizes a northern form, Quercus macrocarpa var. olivaeformis, whose acorns are about half the size of the southern form and whose cup is much thinner and smaller. It lists hybrids with nine species, including white oak, swamp white oak, overcup oak, chinkapin oak and post oak.

Wood

Silvics says the wood is commercially valuable and marketed as white oak. The Wood Handbook (FPL-GTR-282, 2021) describes the white oak group on the white oak page, and its Table 5-3b has a separate bur oak row, shown below.

Wood Handbook Table 5-3b	Specific gravity	Modulus of rupture (lbf per square inch)	Side hardness (lbf)
Green	0.58	7,200	1,110
At 12% moisture content	0.64	10,300	1,370

The Wood Handbook states that specific gravity is based on oven-dry weight and the volume when green or at 12% moisture content. The green weight of the wood without bark is in the NRS-38 table, the same figure used in the log weight calculator.

Diseases, insects and damage the handbook names

Silvics (1990) names these agents by the names it used.

Defoliators and scale. The redhumped oakworm, oak webworm, oak skeletonizer, a leaf miner, the variable oakleaf caterpillar, June beetles and the oak lacebug, which the handbook says may heavily defoliate bur oaks in shelterbelt plantings, especially during dry weather. Bur oak kermes may distort leaves and kill twigs.
Oak wilt. Ceratocystis fagacearum is described as a less serious problem in bur oak than in the red oak group. The handbook says spread from an infected bur oak to adjacent oaks is infrequent, but that the disease sometimes spreads through root grafts and entire groves have been killed by gradual expansion from one center of infection. See oak wilt and oak wilt by state and province.
Cankers and root rots. Susceptible to cotton root rot (Phymatotrichum omnivorum) and Strumella canker (Strumella coryneoidea); in one Pennsylvania plantation half of the trees became infected with the latter and nearly a fourth of these died. Other fungi isolated from diseased parts include Dothiorella canker and dieback, Phoma canker, Coniothyrium dieback and shoestring root rot (Armillaria mellea).
Fire, drought and flooding. The handbook says large bur oaks are resistant to injury by fire, which together with resistance to drought and disease probably accounts for the maintenance of the bur oak openings in southern Wisconsin, and credits thick fire-resistant bark for the presence of large bur oaks in the Big Woods of Minnesota. It says bur oak is not resistant to flooding: in two areas where it was permanently flooded it died within 3 years. The species tolerates urban pollution better than most oaks.

The guide on reporting a pest in the United States and the Canada reporting page give the offices that take sightings of regulated pests. Who may apply pesticides is in pesticide licences by country.