What Is A Bur Oak Tree: Learn About Bur Oak Care In Landscapes
By: Teo Spengler
Mighty and majestic, the bur oak (Quercus macrocarpa) is a survivor. Its massive trunk and rough bark help it exist in a very broad natural range in a variety of habitats – from wet bottomlands to dry uplands. What is a bur oak? Read on for bur oak information and tips on bur oak care.
What is a Bur Oak?
Bur oaks, also called mossycup oak, are decidedly impressive oak trees native to North America. They grow in the wild in central and eastern sections of the continent. The common names comes from a mossy scale, or bur, on the acorn cup rim.
Bur Oak Information
Bur oak trees are medium to large sized trees. They are deciduous members of the white oak group and grow to heights between 60 and 150 feet tall (18 to 46 m.). If you are thinking of planting a bur oak, you’ll want to take height into account when selecting a site. Keep in mind that the trees also have broad, rounded crowns.
Bur oak trees produce yellow catkin flowers in springtime, but they are not particularly showy. The acorns are oval with fringed cups, and offer a good food source for wildlife, including both birds and mammals.
Don’t expect brilliant fall color in bur oak tree leaves. The green leaves turn a dull yellow-brown before they fall.
Planting a Bur Oak
Planting a bur oak is only a good idea for homeowners with very large backyards, given the size of the trees. The massive oak grows best in U.S Department of Agriculture zones 3 through 8. Be sure you site the tree with enough room to grow and in a permanent location. Bur oak information says that these native trees can live up to 300 years.
If you do decide to start planting a bur oak, site the tree in full direct sun. Be sure the tree gets at least six hours of unfiltered sunlight every day.
For best bur oak care, plant the tree in soil that is well drained and loamy. It will grow in either acidic or alkaline soil, and tolerates sandy, wet, and clay soils too.
And speaking of bur oak care, don’t forget to water the tree regularly, especially during its first year in your garden. Bur oak trees have some drought tolerance, but they will grow faster and healthier with moderate moisture.
Note that bur oak trees tolerate city smoke and other air pollutants as well as compacted soil. They are often used as shade trees on U.S. city streets.
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Read more about Oak Trees
The hardiest of the oaks, this shade tree is singularly majestic, with its picturesque wide-spreading habit of growth and gnarled branches, best for larger landscapes extremely tough and adaptable but relatively slow growing, plant for future generations
Bur Oak has dark green foliage throughout the season. The glossy lobed leaves turn coppery-bronze in fall. Neither the flowers nor the fruit are ornamentally significant. However, the fruit can be messy in the landscape and may require occasional clean-up. The furrowed black bark adds an interesting dimension to the landscape.
Bur Oak is a dense deciduous tree with a more or less rounded form. Its relatively coarse texture can be used to stand it apart from other landscape plants with finer foliage.
This tree will require occasional maintenance and upkeep, and is best pruned in late winter once the threat of extreme cold has passed. It is a good choice for attracting squirrels to your yard. Gardeners should be aware of the following characteristic(s) that may warrant special consideration
Bur Oak is recommended for the following landscape applications
Bur Oak will grow to be about 80 feet tall at maturity, with a spread of 80 feet. It has a high canopy of foliage that sits well above the ground, and should not be planted underneath power lines. As it matures, the lower branches of this tree can be strategically removed to create a high enough canopy to support unobstructed human traffic underneath. It grows at a slow rate, and under ideal conditions can be expected to live to a ripe old age of 300 years or more think of this as a heritage tree for future generations!
This tree should only be grown in full sunlight. It is very adaptable to both dry and moist locations, and should do just fine under average home landscape conditions. It is considered to be drought-tolerant, and thus makes an ideal choice for xeriscaping or the moisture-conserving landscape. It is not particular as to soil type or pH. It is somewhat tolerant of urban pollution. This species is native to parts of North America.
The Mighty Bur Oak
Few species of trees have such a universally recognized name as the Oak. Worldwide, there are some 600 species of Oaks, and in Ohio alone we have over a dozen. Here in Columbus, they tower over the homes of Clintonville, line the streets of Upper Arlington, and bathe the yards of Bexley with their shade. Oaks in Ohio can be divided into two groups - Red Oaks and White Oaks. Many of the large Oaks we see throughout the city in urban landscapes are of the Red Oak group. Less commonly planted are Oaks in the White Oak group, of which the Bur Oak belongs. Let’s take a closer look at this under-utilized tree that is native to most parts of our state.
The Bur Oak, sometimes spelled Burr Oak and alternatively named the Mossycup Oak, is a large shade tree at maturity, growing to 80 feet or more in height and spread. For this reason, the proper siting of this tree in the urban landscape is essential. There’s an old saying, “A society grows great when old men plant trees in whose shade they know they shall never sit.” I think it’s equally true to say that a property grows in beauty and value when it’s owner plants trees with consideration for a mature size that he/she will likely never see. Bur Oaks get BIG. They also have one of the largest acorns of the Oaks, another consideration when deciding where to plant.
Chlorosis in a Pin Oak in Bexley, Ohio
One of the characteristics that I love about this tree is that it tolerates, and even prefers, slightly alkaline soils. A common problem we as arborists see in landscapes everyday throughout Central Ohio is chlorosis, or yellowing of tree leaves due to nutrient deficiencies, which leads to slow decline and potential death of a tree. Because we tend to have higher pH levels, certain micronutrients, although present in the soil, become less available for uptake by plants, and some trees are more sensitive to this. We often see this in Oaks of the Red Oak group like Red Oak and Pin Oak, two very common landscape trees. Because a higher pH level of the soil isn’t an issue for Bur Oaks, they typically avoid the problem of chlorosis.
Another notable characteristic of Bur Oaks is that they do exceptionally well on their own. In their native habitat, Bur Oaks are often found growing in a more open area where they develop large, strong lateral limbs. One reason this may occur is because of their ability to grow in adverse conditions that other trees won’t tolerate. This makes them suitable for the urban landscape where we often plant large shade trees as stand-alone additions in the yard.
Last but not least, because the Bur Oak is a member of the White Oak group it tends to be less susceptible to Oak Wilt. Oak Wilt is a vascular disease caused by a fungus, and can lead to the decline and death of otherwise healthy Oak trees. Because of its continued spread, it is unfortunately something we’re now having to take into consideration with how we care for Oak trees in Central Ohio. Considering a Bur Oak or other White Oak species for your landscape is a simple step towards reducing the prevalence of this disease.
The Bur Oak might just be the perfect shade tree for less than perfect conditions. Consider this quick list of pros and cons in deciding whether it’s the right tree for your landscape:
Large size, long-lived, and a dominant landscape feature at maturity, not appropriate for small yards
Beautiful, majestic habit when mature
Tolerant of soil conditions that adversely affect some common species of Oak, notably high soil pH
Less susceptible to Oak Wilt, a disease of growing concern in Central Ohio
Large fruit (acorns) that may not be preferred near driveways or over a home
Does not transplant as well, so it’s sometimes hard to find at nurseries and garden centers
Walter Reins | Regional Manager, Russell Tree Experts
Walter has been an ISA Certified Arborist since 2003. He graduated from Montgomery College in Maryland with a degree in Landscape Horticulture, and has called Columbus, OH his home for nearly 20 years. Walter appreciates trees for their majesty and the critical role they play in our world.
Description & Overview
The iconic oak of Wisconsin! Bur Oak is one of the toughest oaks, tolerant of highly alkaline soils and drought. Most have interesting corky bark on young branches. The acorns make it an excellent plant to attract wildlife. Use where space is not limiting as Bur Oak is large at maturity and long-lived. May also be known as Blue Oak, Mossycup Oak.
Ecologcial Value Rating
Bur Oak is a large, long-lived tree, so be conscious of the available space. The tree is sturdy and not likely to shed branches, making it ideal for parks or medians where there is enough space for the tree to reach its mature size. Bur Oak also functions well as a shelter belt tree due to its low moisture needs and indifference to soil types.
Bur Oak tolerates very high soil alkalinity and is one of, if not the best oak trees for tough urban sites. It is also drought and pollution tolerant, indifferent to soil quality, and requires little maintenance once established.
Salable #25 Container Bur Oak. Pictures taken mid-August.
Leaf and acorn measurements on a salable #25 Container Bur Oak. Pictures taken mid-August.
Salable #25 Container Bur Oak.
Bur Oaks, like all oaks in the White Oak Group, have less tannin in their acorns than those in the Red Oak Group. This makes them more palatable (less bitter) and preferable to wildlife. Blue jays and crows will flock to the tree for the acorns. Deer, squirrels, chipmunks, and other small mammals love the acorns as a food source.
All oaks are susceptible to Two-Lined Chestnut Borer during the establishment period after planting. Apply a systemic insecticide containing imidacloprid to Bur Oak when planting to protect the tree from this insect.
Don’t prune Bur Oak during the growing season. While not as susceptible to Oak Wilt as those in the Red Oak Group, the disease can still damage stressed trees. Prune only during the dormant season in winter after the leaves have fallen.
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.
Left: Amazing central leader system. Right: Corky, interesting bark on exposed branches.
When healthy, Bur Oak has few significant disease or insect problems. Occasionally the leaves can be defoliated by Gypsy Moth and June Bugs. Avoiding damage and wounds during the growing season will prevent Bur Oak from being infected by Oak Wilt. Bur Oak Blight can infect the tree in periods of stress, and the native Wisconsin variety of Bur Oak is more susceptible than the southern ecotype. However, disease resistance varies between plants and some trees exhibit high resistance to this fungal disease.
The most important care for Bur Oak is to maintain health and vigor through good mulching and adequate watering. During the first two years after planting, make sure the tree has enough moisture to properly establish its roots. Use a systemic insecticide to protect it from Two-Lined Chestnut Borer.
If stressed, Bur Oak is susceptible to attack by Two-Lined Chestnut Borer, Oak Webworm, Leaf Miners, Oak Skeletonizer, Variable Oakleaf Caterpillar, Cotton Root Rot, and Strumella Canker. All of these pests and diseases can be avoided if the tree is properly cared for.
When grown naturally, Oaks develop a coarse, deep root system with a taproot. This has made them historically difficult to transplant as balled-and-burlapped (B&B) trees because much of the root system is lost in the harvesting process. Our trees are unique because they are root pruned from the start to develop more fibrous fine roots. When harvested, our B&B oaks contain more fibrous roots, making them tougher and easier to transplant than oaks not given our unique treatment process.
Bur Oak is noted for having the largest acorn of all native Oak species. In Wisconsin, however, our Bur Oaks are of the oliviformis variety, which has smaller acorns than the species. While not as large as the acorns of the southern ecotype, the acorns of our native variety are more manageable in a landscape setting and create less mess.
The wood of Bur Oak is commercially valuable for its rot resistance and strength. It is typically sold commercially as White Oak.
Bur Oak is a pioneer species at the forest edge and will invade prairies along with Northern Pin Oak. The corky bark of Bur Oak protects it against the wildfires that distinguish our native tallgrass prairies, even when young.
Of all the native North American oaks, Bur Oaks bear acorns the longest- a 400 year old tree will still reliably produce seeds. Bur Oak is a mast species- it produces acorns at irregular frequencies to help it reproduce. During years of regular production, the tree produces enough acorns to sustain a local population of small wildlife that will eat the seeds. When the trees produce a bumper crop of seeds, animals will cache large amounts of acorns but will not be able to eat them all. The uneaten acorns are thus ‘planted’ by wildlife and result in forests that have trees in similar age groups. While other oaks, like White Oak, tend to have little to no production between heavy seed years, Bur Oak is more consistent in its intervals and production, providing value to wildlife even in years of low production.
In forest margins, Bur Oak is associated with American Filbert, Smooth Sumac, Prairie Crabapple, and Coralberry.
To mimic a prairie environment, consider planting Ironweed, Big Bluestem, Little Bluestem, Butterflyweed, Leadplant, and Prairie Dock.
Five Oaks for the Kansas Landscape
The strongest oak of the forest is not the one that is protected from the storm and hidden from the sun. It’s the one that stands in the open where it is compelled to struggle for its existence against the winds and rains and the scorching sun. – Napoleon Hill
If you live in Kansas long enough, you really begin to appreciate trees. They endure heat and extreme cold along with persistent wind. Months without rain are common, but so is the occasional soaking rain that saturates the soil. Trees in this part of the world need to be resilient.
Folks in areas of the country that have an abundance of trees often take trees for granted. Trees grow easily, but not here. A good shade tree in Kansas is a luxury. They need to withstand the rigors of the climate. To sit under a mature tree on a warm afternoon, enjoy the blue skies and sip your favorite cool drink is a special experience.
Here are five oaks trees that are “plains tough”. (This is my list, but there are over 10 species of oaks native to Kansas and several other non-native varieties that are equally tenacious.)
OAK TREES FOR KANSAS
1. Bur oak
When I go fishing along the Cottonwood River, I can’t help but notice the huge Bur oaks (Quercus macrocarpa) stretching out their limbs over the river. West of Hesston, there is one that has a span of over 150 feet. It is quite a specimen. This native oak of the eastern two-thirds of Kansas is one of the most adaptable hardwood trees in Kansas. Generally, it is slow growing, but in the right conditions it can grow two to three feet a year. Mature height is 50 to 80 feet tall and with a spread from 40 to 60 feet. The Bur oaks don’t typically have great fall color, but it is very sturdy and problem-free.
2. White oak
As part of my horticulture classes at Kansas State University, I had to learn the names of many different plants on campus. One of the trees I remember the most is a white oak (Quercus alba) on the east side of campus. It is a beautiful tree with great fall color. This stately tree stood about 60-70 feet tall with a spread of at least 60 feet. I would love to have that white oak in my back yard, because I know that it would be there for generations.
3. English oak
The Kansas state champion English oak (Quercus robur) is in Kinsley. If it can grow in Kinsley, it can grow anywhere in the state. It is native to Europe, but a versatile tree in Kansas. Typical growth is 30 to 50 feet in height and 30 to 40 feet in spread. Leaves are dark green throughout the year. They eventually turn brown, but stay on the tree much of the winter. This tree adapts to most soil types, including heavy clay. Ours at the arboretum puts on good growth each year – one to two feet. Give it room to grow and you will be rewarded with an excellent shade tree.
4. Shumard (red) oak
The fastest growing member of the red oak family is Shumard oak (Quercus shumardii) making it a great choice for the home landscape. Its native range is eastern Kansas along moist streams and upland rocky hillsides. It is quite adaptable to a wide range of soil conditions. The fall color can be incredible. It is recommended that you choose your tree in the fall when they are coloring because the species can be variable in fall color intensity. Shumard oaks are more tolerant than other red oaks of urban areas and challenging sites.
5. Shingle oak
Our shingle oaks (Quercus imbricaria) this fall have been spectacular. The red fall color was more brilliant than in previous years. The color fades, but the leaves will persist through most of the winter. Speaking of the leaves, they are unusual among oaks. They don’t have lobes, but are smooth along the margins. It is a great form that can thrive in drier conditions. They grow 40 to 60 feet tall and spread 30 to 50 feet.