Lady Bird Johnson Wildflower Center - The University of Texas at Austin information

 Native Plant Database

Quercus macrocarpa


Bur oak, Burr oak, Savannah oak, Overcup oak, Prairie oak, Mossy-cup oak, Mossy-overcup oak, Blue oak


Fagaceae (Beech Family)



Quercus macrocarpa (Bur oak)
Waitt, Damon E.
Bur oak is a large, deciduous tree with a very wide, open crown. Usually wider than tall, the tree can exceed 100 ft. in height and width. The massive trunk supports heavy, horizontal limbs and rough, deep-ridged bark. Leaves up to 9 inches long with a central midrib from which branch veins lead into rounded lobes. Lobes separated by deep sinuses reaching, in some cases, to within 1/2 inch of the midrib. Lobes beyond the midpoint of the blade wavy margined and longer and broader than those toward the base. Acorns large, up to 1 1/2 inches broad with 1/4 to more than 1/2 of the acorn enclosed in the cup. Cup with coarse scales and a fringed margin.

The acorns of this species, distinguished by very deep fringed cups, are the largest of all native oaks. The common name (sometimes spelled Burr) describes the cup of the acorn, which slightly resembles the spiny bur of a chestnut. Bur Oak is the northernmost New World oak. In the West, it is a pioneer tree, bordering and invading the prairie grassland. Planted for shade, ornament, and shelter belts. Bur oak extends farther north than any other oak species and becomes shrubby at the northern and eastern limits of its range.

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Plant Characteristics

Duration: Perennial
Habit: Tree
Leaf Retention: Deciduous
Leaf Arrangement: Alternate
Leaf Complexity: Simple
Leaf Shape: Elliptic , Obovate
Leaf Venation: Pinnate
Leaf Margin: Lobed
Leaf Base: Cuneate , Rounded
Breeding System: Flowers Unisexual , Monoecious
Inflorescence: Catkin
Fruit Type: Nut
Size Notes: Slow growing, large tree that grows to 100 feet (30.5 m).
Leaf: Leaves dark green above, grayish-green with finely dense pubescence below.
Autumn Foliage: yes
Fruit: Acorns annual; 1 - 3 acorns on stout peduncle 1⁄4 - 3⁄4 inch (6 - 19 mm) long; deep cup with grayish pubescent scales, scales near cup rim forming a fringe around the nut, enclosing 1⁄2 - 7⁄8 of nut; light brown, broadly elliptical nut, finely pubescent, 1 - 2 inches (25 - 51 mm) - 54 - long.
Size Class: 36-72 ft. , 72-100 ft.

Bloom Information

Bloom Color: Yellow , Green , Brown
Bloom Time: Mar , Apr , May

Distribution

USA: AL , AR , CT , DE , IL , IN , IA , KS , KY , LA , ME , MD , MA , MI , MN , MS , MO , MT , NE , NH , NJ , NM , NY , ND , OH , OK , PA , RI , SD , TN , TX , VT , VA , WV , WI , WY , DC
Canada: AB , MB , NB , ON , QC , SK
Native Distribution: Saskatchewan east to New Brunswick, southwest to Texas, and north to Montana.
Native Habitat: Prairies; open woods; sandy ridges; stream edges. Widely distributed and capable of withstanding a wide range of harsh conditions (one of the most drought resistant oaks) throughout eastern North America; usually found on limestone or calcareous clay.

Growing Conditions

Water Use: Medium
Light Requirement: Sun , Part Shade , Shade
Soil Moisture: Wet , Moist , Dry
Soil pH: Acidic (pH<6.8)
CaCO3 Tolerance: Medium
Cold Tolerant: yes
Soil Description: Various soils & moisture conditions. Sandy, Sandy Loam, Medium Loam, Clay Loam, Clay, Caliche type, Limestone-based
Conditions Comments: The species name macrocarpa, refers to the golf ball sized acorns of this tree. The leaves of bur oak also are large, so they are easy to rake. Bur oak is drought resistant, long-lived and reasonably fast-growing for an oak. Tolerates limey soils better than other oaks. Resistant to oak wilt and a number of other problems. Sensitive to root zone disturbance caused by construction.

Benefit

Use Ornamental: Shade tree, Attractive, Fast growing, Long-living. A good urban tree since it is resistant to air pollution and car exhaust.
Use Wildlife: Attracts songbirds, ground birds and mammals. Substrate-insectivorous birds, Fruit-birds, Fruit-mammals, Fruit-rodents, Fruit-deer.
Use Food: Acorns (nuts) are edible after tannins are leached or boiled out. Gather nuts during the fall from September to October. Only gather the ripe tan-to-brown acorns, rather than the unripe green ones. remove bitterness, shell the brown, ripe acorns and remove any corky skin layers, dice the meat, and boil the chunks in water from 15 to 30 minutes until the water turns brown. Then pour off the water and repeat the process until the water clears, indicating that the tannic acid has been removed. During the last boiling, salt water can be added; then the acorns can be deep fried or mixed in a soup. Finely chopped acorn meats can be added to bread doughs and muffin batters. After the leaching process, acorn meat can be frozen. To make flour, the boiled acorn meat can be split in two and dried by slowly baking in a 200 degree oven with the door cracked to allow moisture to escape. Crush or grind and use as a thickener or a flour. Another method is to roast the fresh acorn to work well in a grinder or blender. After grinding, place the flour into a cloth bag and boil to leach out bitterness. Leached acorns, after they are roasted until brittle, can be ground and used as a marginal coffee substitute.
Use Medicinal: Native Americans used bur oak as medication for heart problems and other ailments.
Use Other: This oak’s wood quality is similar to white oak and is often used for construction, flooring, and cooperage.
Warning: Acorns (seeds of nuts) and young leaves have low toxicity if eaten. Symptoms include stomach pain, constipation and later bloody diarrhea, excessive thirst and urination.
Interesting Foliage: yes
Attracts: Butterflies
Larval Host: Edwards Hairstreak, Horaces Duskywing butterfly
Deer Resistant: No

Last Update: 2012-05-09