bur oak

(Quercus macrocarpa var. macrocarpa)

               
Conservation Status

IUCN Red List

LC - Least Concern

bur oak (var. macrocarpa)

NatureServe

N4N5 - Apparently Secure to Secure

SNR - Unranked

Minnesota

not listed

Wetland
Indicator
Status

Great Plains

FACU - Facultative upland

Midwest

FAC - Facultative

Northcentral & Northeast

FACU - Facultative upland

Nativity

Native

 
Occurrence

Very common and widespread

 
Habitat

Moist to wet; drought tolerant. Prairie borders, dry hillsides, river valleys, savannas, bottomlands. Full to partial sun.

 
Flowering

May to early June

     
Flower Color

Green

     
Height

50 to 80

     

Identification

This is a slow growing, long-lived, deciduous tree rising on a single trunk from a taproot and widely spreading roots. The root system is massive—the weight of the root system equals the weight of the above-ground growth of the tree. In Minnesota mature trees are usually 50 to 80 tall and up to 43 in diameter, though individuals can reach over 100 in height.

In open areas with deep soil the trunk is straight and is distinct to the upper crown. In less favorable conditions the trunk splits into heavy, gnarled, ascending branches.

The branches are ascending to spreading; ascending in the upper part of the crown, nearly horizontal in the lower part. The crown of young trees is tall and oval with a rounded top. In open areas the crown of mature trees can be very broad.

The bark on young trees is rough. On mature trees the bark is thick and ashy gray, with deep furrows and ridges that are broken into irregular, dark gray scales.

The twigs are stout, yellowish- to grayish-brown, and slightly hairy. Branchlets often develop flat, radiating, corky wings. Terminal buds are reddish-brown, hairless, round, 1 16 to ¼ long, and blunt at the tip. Lateral buds are 1 16 to 3 16 long and are closely appressed to the twig.

The leaves are alternate, leathery, 4 to 8 long, 2¾ to 6 wide, and inversely egg-shaped in outline but otherwise variable in shape. They are on hairy leaf stalks that may be to 13 16 long, but are usually to 1long. The leaf blade is rounded or wedge-shaped at the base. There are 2 to 6 large, irregular, rounded, primary lobes and 2 to 10 smaller, rounded, secondary lobes or rounded teeth per side. The deepest sinuses, near the center of the blade, are usually very deep, extending 50% to 90% of the way to the midvein. Most leaf blades are fiddle-shaped, with a broad, expanded, shallowly lobed upper half (terminal lobe) above a deep sinus and a few short lobes on the lower half. The upper surface is dark green, shiny, and hairless or sparsely hairy. The lower surface is pale green or gray and densely hairy with short, appressed, star-shaped hairs, making it velvety to the touch.

Male and female flowers are borne on the same tree. Male flowers are in slender, ¾ to 2 long catkins that hang downward from buds on branchlets of the previous year. Female flowers appear in clusters of 1 to 3 on a short stalk rising from leaf axils of the current year’s twigs. The flowers appear after the leaves in May to early June.

The fruit is a large, narrowly egg-shaped to flattened egg-shaped, 9 16 to long, to wide acorn. This is the largest acorn of any of the native oaks. They are in clusters of 1 to 3 acorns on a short, stout stalk. A scaly, dome-shaped cup encloses ½ to or more of the lower part of the nut. There is a conspicuous fringe of soft, curly, 3 16 to long awns along the rim of the cup, which gives this tree its common name. The inside of the acorn cup is uniformly hairy. The nuts ripen in early August to early mid-September of the first year. It tastes sweet or slightly bitter.

 
Record

The champion bur oak in Minnesota is on private property in or near Rochester, in Olmsted County. In 1999 it was measured at 60 tall and 275 in circumference (87½ in diameter).

 
Similar
Species

Bur oak (Quercus macrocarpa var. depressa) is found along the western margin of the Great Plains. It is a shrub or small tree no taller than 16 that occurs on bluffs and hillsides. The acorns are smaller with smaller, less fringed cups.

White oak (Quercus alba) bark is thin and fine-textured. The branchlets do not have corky ridges. The lateral buds diverge from the twig. The leaves are more uniformly lobed and never has a large terminal lobe. The underside of the mature leaf is hairless or has a few hairs along the main veins. The acorn cup encloses only the lower ¼ to ½ of the nut, and does not have a fringe of awns along the rim.

 
Pests and Diseases

Jumping oak gall wasp (Neuroterus saltatorius) appears as small, BB-sized growths on the underside of leaves and wart-like brown spots on the upper surface of leaves of oaks in the white oak section.

Oak flake gall wasp (Neuroterus floccosus) causes fuzzy, buff to light brown galls along the veins on the underside of leaves and buff, wart-like bumps on the upper surface of leaves of oaks in the white oak section.

Oak Leaf Blister (Taphrina caerulescens) is a fungus that causes blister-like galls on the upper leaf surface.


Distribution Distribution Map   Sources: 7.

Comments

Bur oak is the most common oak and one of the most common trees in Minnesota. It is the official State Tree of Iowa.


Taxonomy

Family:

Fagaceae (beech)

 

Subfamily:

Fagoideae

 

Genus:

Quercus

 

Subgenus:

Quercus

 

Section:

Quercus (white oak)

 
Parent

bur oak (Quercus macrocarpa)

 
Synonyms

 

 
Common
Names

blue oak

bur oak

mossy over-cup oak

scrub oak


 

 

 

 

 

 

 

 

 

 

 

Glossary

catkin

A slim, cylindrical, drooping cluster of many flowers. The flowers have no petals and are either male or female but not both.

       

Visitor Photos

   
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Randy


Bur oak bark

  bur oak (var. macrocarpa) and black cherry    
       

Twin trunks, black cherry on left, bur oak on right

  bur oak (var. macrocarpa) and black cherry    
       

The strong branching even in the upper reaches of a towering bur oak

  bur oak (var. macrocarpa)    

       
       
       

MinnesotaSeasons.com Photos

   

Tree

  bur oak (var. macrocarpa)   bur oak (var. macrocarpa)
       

Leaf

  bur oak (var. macrocarpa)   bur oak (var. macrocarpa)
       
  bur oak (var. macrocarpa)   bur oak (var. macrocarpa)
       

Twisted Branches

  bur oak (var. macrocarpa)    
       

Acorn Cup

  bur oak (var. macrocarpa)   bur oak (var. macrocarpa)
       
       

 

Camera

     

Slideshows

   
  Quercus macrocarpa
Matt Lavin
 
  Quercus macrocarpa  
 
About

Bur Oak

 
     
  Bur Oak
J.Steinbock
 
  Bur Oak  

 

slideshow

     

Visitor Videos

   
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Other Videos

 
  Trees with Don Leopold - bur oak
ESFNature
 
   
 
About

Published on Dec 12, 2013

Don Leopold demonstrates the characteristics of bur oak.

Content produced by Christopher Baycura for the SUNY College of Environmental Science and Forestry (SUNY-ESF).

 
     
  How to ID Quercus macrocarpa
How to ID Quercus macrocarpa
 
   
 
About

Uploaded on Nov 19, 2008

Short video with the top identifying characteristics for Quercus macrocarpa

 
     
  Burr Oak.mov
Kimberly Wade
 
   
 
About

Uploaded on Sep 9, 2010

Richard Weber, owner of Springhouse Gardens, talked about the Burr Oak during a Tree Walk hosted at The Lexington Cemetery. The Lexington Cemetery is home to more than 200 species of trees.

 
     

 

Camcorder

         

Visitor Sightings

   
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Randy
12/22/2016

Location: Freeborn Co.

Bur oak bark

bur oak (var. macrocarpa) and black cherry


Randy
12/12/2016

Twin trunks, black cherry on left, bur oak on right

bur oak (var. macrocarpa) and black cherry


Randy
11/16/2016

The strong branching even in the upper reaches of a towering bur oak

bur oak (var. macrocarpa)


     
     
 

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