Quercus macrocarpa

Many birds and animals depend on the acorns and foliage of Quercus macrocarpa for food, and the tree for cover.

Photo Credit: © USDA-NRCS PLANTS Database / Herman, D.E., et al. 1996. North Dakota tree handbook. USDA NRCS ND State Soil Conservation Committee; NDSU Extension and Western Area Power Administration, Bismarck.

Quercus macrocarpa

Common Name: bur oak

Plant Functional Group: Deciduous broadleaf

Class > Order > Family: Magnoliopsida > Fagales > Fagaceae

What does the species look like?

Bur oak is a deciduous large shrub to large tree growing 70 to 100 feet tall, or more. Male and female flowers are separate on the same tree. Many tiny male flowers are grouped into yellow-green, caterpillar-like clusters (catkins) that hang down. The tiny female flowers occur on a small spike and are surrounded by a green, red-tinged cupule (what will become the acorn cap). Flowering begins when plants become mature about 35 years of age. Flowers are wind- and self-pollinated.

Bur oak is found in a range of habitats and moisture regimes, on valley floors, bottomlands, prairies, oak savannas, riparian slopes and terraces, upland woods, forests, and rocky bluffs. It is tolerant of air pollutants and drought resistant. It is relatively intolerant of flooding, although it can occur in poorly drained soils.

Where is the species found?

States & Provinces

AB, AL, AR, CT, DC, DE, IA, IL, IN, KS, KY, LA, MA, MB, MD, ME, MI, MN, MO, MS, MT, NB, ND, NE, NH, NJ, NM, NY, OH, OK, ON, PA, QC, RI, SD, SK, TN, TX, VA, VT, WI, WV, WY

Special Considerations for Observing

If drought seems to be the cause of leaf color or fall for a plant, please make a comment to that effect.

Note that individuals may not produce catkins every year.

Which phenophases should I observe?

	Do you see...?
Leaves	Breaking leaf buds One or more breaking leaf buds are visible on the plant. A leaf bud is considered "breaking" once a green leaf tip is visible at the end of the bud, but before the first leaf from the bud has unfolded to expose the leaf base at its point of attachment to the leaf stalk (petiole) or stem. More... How many buds are breaking? Less than 3 3 to 10 11 to 100 101 to 1,000 1,001 to 10,000 More than 10,000
	Leaves One or more live, unfolded leaves are visible on the plant. A leaf is considered "unfolded" once its entire length has emerged from a breaking bud, stem node or growing stem tip, so that the leaf base is visible at its point of attachment to the leaf stalk (petiole) or stem. Do not include fully dried or dead leaves. More... What percentage of the potential canopy space is full with leaves? Ignore dead branches in your estimate of potential canopy space. Less than 5% 5-24% 25-49% 50-74% 75-94% 95% or more
	Increasing leaf size A majority of leaves on the plant have not yet reached their full size and are still growing larger. Do not include new leaves that continue to emerge at the ends of elongating stems throughout the growing season. More... What percentage of full size are most leaves? Less than 25% 25-49% 50-74% 75-94% 95% or more
	Colored leaves One or more leaves show some of their typical late-season color, or yellow or brown due to drought or other stresses. Do not include small spots of color due to minor leaf damage, or dieback on branches that have broken. Do not include fully dried or dead leaves that remain on the plant. More... What percentage of the potential canopy space is full with non-green leaf color? Ignore dead branches in your estimate of potential canopy space. Less than 5% 5-24% 25-49% 50-74% 75-94% 95% or more
	Falling leaves One or more leaves with typical late-season color, or yellow or brown due to other stresses, are falling or have recently fallen from the plant. Do not include fully dried or dead leaves that remain on the plant for many days before falling. More...
Flowers	Flowers or flower buds One or more fresh open or unopened flowers or flower buds are visible on the plant. Include flower buds or inflorescences that are swelling or expanding, but do not include those that are tightly closed and not actively growing (dormant). Also do not include wilted or dried flowers. For Quercus macrocarpa, the male inflorescence is a catkin which is initially compact and stiff, but eventually unfolds to become longer and hang loosely from the branch. Female flowers are very small and petal-less, emerging from the growing stem at the point where a new leaf is attached. More... How many flowers and flower buds are present? For species in which individual flowers are clustered in flower heads, spikes or catkins (inflorescences), simply estimate the number of flower heads, spikes or catkins and not the number of individual flowers. Less than 3 3 to 10 11 to 100 101 to 1,000 1,001 to 10,000 More than 10,000
	Open flowers One or more open, fresh flowers are visible on the plant. Flowers are considered "open" when the reproductive parts (male stamens or female pistils) are visible between or within unfolded or open flower parts (petals, floral tubes or sepals). Do not include wilted or dried flowers. For Quercus macrocarpa, the male flowers will open once the initially compact catkin has unfolded and is hanging loosely. Female flowers are open when the pistils are visible, but will be very difficult to see where they are out of reach. More... What percentage of all fresh flowers (buds plus unopened plus open) on the plant are open? For species in which individual flowers are clustered in flower heads, spikes or catkins (inflorescences), estimate the percentage of all individual flowers that are open. Less than 5% 5-24% 25-49% 50-74% 75-94% 95% or more
	Pollen release One or more flowers on the plant release visible pollen grains when gently shaken or blown into your palm or onto a dark surface. More... How much pollen is released? Little: Only a few grains are released. Some: Many grains are released. Lots: A layer of pollen covers your palm, or a cloud of pollen can be seen in the air when the wind blows
Fruits	Fruits One or more fruits are visible on the plant. For Quercus macrocarpa, the fruit is a nut (acorn), partially covered with a fringed "cap", that changes from green to light brown, dark red brown or dark grayish. More... How many fruits are present? Less than 3 3 to 10 11 to 100 101 to 1,000 1,001 to 10,000 More than 10,000
	Ripe fruits One or more ripe fruits are visible on the plant. For Quercus macrocarpa, a fruit is considered ripe when it has turned light brown, dark red brown or dark grayish. More... What percentage of all fruits (unripe plus ripe) on the plant are ripe? Less than 5% 5-24% 25-49% 50-74% 75-94% 95% or more
	Recent fruit or seed drop One or more mature fruits or seeds have dropped or been removed from the plant since your last visit. Do not include obviously immature fruits that have dropped before ripening, such as in a heavy rain or wind, or empty fruits that had long ago dropped all of their seeds but remained on the plant. More... How many mature fruits have dropped seeds or have completely dropped or been removed from the plant since your last visit? Less than 3 3 to 10 11 to 100 101 to 1,000 1,001 to 10,000 More than 10,000

What do these phenophases look like?

There is currently no photoguide available for this species. If you'd like help us create one, use the guidance document and species template provided here. Then send it via email to education@usanpn.org when it is complete.

ITIS information for bur oak (ITIS TSN: 19287 )

USDA PLANTS profile for bur oak (USDA Symbol: QUMA2 )

Quercus macrocarpa

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