Notable Oaks of the U.S. Capitol Grounds

Landscape architect Frederick Law Olmsted's 1874 General Plan for the U.S. Capitol Grounds sought to create a setting to accentuate the monumentality of the Capitol itself. Trees were heavily used in Olmsted's design to frame the building and to provide shade for visitors, creating a natural landscape as opposed to focusing on individual plants or formal gardens.

The grounds today feature a collection of more than 4,000 trees throughout the entire 286-acre Capitol campus and is a Level III-accredited arboretum recognized by ArbNet. Many of the trees that remain from Olmsted's time are various types of oaks, and there are 40 different species of oaks (Quercus spp.) currently on the U.S. Capitol Grounds.

"There's an oak for every microclimate on the grounds,” says Dana Gresham, Urban Forester for the Architect of the Capitol (AOC). "Quercus bicolor (swamp white oak) and Quercus lyrata (overcup oak) do great in low spots with wet soil, Quercus montana (chestnut oak) is happy on a drier slope and Quercus phellos (willow oak) can thrive just about anywhere."

The oak has been the United States' national tree since 2004 and oaks are also the official tree of six states: Connecticut, Georgia, Illinois, Iowa, Maryland and New Jersey; plus, the official tree of our capital city, Washington, D.C.

Below are just a few of the notable oaks found on the U.S. Capitol Grounds.

Bur Oak (Quercus macrocarpa)

One of the oldest trees on the U.S. Capitol Grounds is a bur oak found near the Grant Memorial. It has been growing in this location since the establishment of the U.S. Botanic Garden (USBG) collections around 1850. There are also three bur oak trees from Olmsted's time (1874) still living on the campus today.

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Photo by

Luke Walter

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This bur oak is officially the biggest tree on the U.S. Capitol Grounds this year.

Photo by

Thomas Hatzenbuhler

One of the oldest trees, an original Olmsted tree and the biggest tree on the U.S. Capitol Grounds are all bur oaks.

Photos by

Luke Walter and Thomas Hatzenbuhler

Another bur oak, in Union Square, was the biggest tree on campus in 2025. "Biggest" was determined using the National Champion Tree Program's formula including DBH (trunk diameter measured at breast height), canopy spread and height.

"It's a perfectly round, broad spreading oak like you'd see drawn in a children's book," says Gresham. "What really sets it apart is the branching habit... The average spread from one edge of the canopy to the other was 113'."

Northern Red Oak (Quercus rubra)

Native to the region, and once a very popular landscape tree in D.C., the northern red oak is the most abundant oak species on the U.S. Capitol Grounds, with more than 360 individual trees, including one original Olmsted tree.

"As all tree species' native ranges shift north with changing climate, Quercus rubra is no longer suited to D.C. growing conditions," says Gresham. "The good news is that the AOC urban forestry program exercises adaptive management, so we're replacing these trees as they are removed with oak species that are more suitable to current and future climate conditions in the region."

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Photo by

Thomas Hatzenbuhler

Northern red oaks on the U.S. Capitol campus.

Photos by

Thomas Hatzenbuhler and Rodney Norman

The selection of the oak as our national tree was based on a vote sponsored by the Arbor Day Foundation in 2001. In April of that year, a northern red oak was then planted and commemorated on the U.S. Capitol Grounds to represent the "People's Choice for a National Tree."

Swamp White Oak (Quercus bicolor)

The swamp white oak gets its species name "bicolor" (two colors) from its leaves — the tops are dark and glossy while the undersides are light.

"Quercus bicolor leaf undersides have a distinct fuzzy texture which helps trap moisture during high wind and dry weather so it can tolerate drought too," says Gresham. "This fuzz, or 'tomentum,' also helps intercept particulate matter from the air, which washes down in rain making it beneficial in places with poor air quality."

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The September 11 Anniversary Tree in spring, 2025.

Close-up view of swamp white oak leaves; the September 11 Anniversary Tree on the U.S. Capitol Grounds.

Photos by

Susanne Bledsoe and Thomas Hatzenbuhler

A commemorative swamp white oak tree was dedicated on the U.S. Capitol Grounds in 2011, on the 10-year anniversary of the 9/11 attacks.

The swamp white oak is native to all three 9/11 crash site areas: New York City; Arlington County, Virginia; and Somerset County, Pennsylvania. It was chosen among numerous possibilities to be used throughout the 9/11 Memorial in lower Manhattan, where approximately 400 were planted on the plaza around the pools.

White Oak (Quercus alba)

The slow growth of white oak makes them ideally structurally suited for placement near buildings and in landscapes. They also provide the highest ecosystem benefits of any species found in the eastern United States.

"Native oaks generally are some of the most ecologically impactful trees," says Gresham. "Quercus alba for example is said to support over 500 different species of pollinators and wildlife."

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The People of Connecticut Charter Oak on U.S. Capitol Grounds in spring, 2025.

Photo by

Thomas Hatzenbuhler

The U.S. Capitol Grounds State of Connecticut tree during summer and State of Maryland tree during fall.

Photos by

Thomas Hatzenbuhler and Susanne Bledsoe

There is one Olmsted white oak tree still living on the Capitol campus today, plus Connecticut and Maryland have white oaks planted as commemorative trees on the U.S. Capitol Grounds.

These special trees were grown from seedlings of other historic trees before being planted on the grounds as symbols of their states and for their people. The original "Charter Oak" famously hid the Connecticut colony's royal charter in 1687 to protect its freedom from the English crown, and the original "Wye Oak" was the largest white oak tree in Maryland, and the entire United States, until 2002.

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Examples of other oaks on the U.S. Capitol Grounds: Willow oak (Quercus phellos) trunk and roots; pin oak (Quercus palustris) leaves and bark; and chestnut oak (Quercus prinus).

Photos by

Susanne Bledsoe

The oaks of the U.S. Capitol Grounds stand as living monuments to our nation's history, resilience and natural heritage. From the oldest oaks planted in Olmsted's era to more recent commemorative trees honoring pivotal moments and people, each oak embodies a legacy of strength and adaptability.

Their presence reminds us that history is all around us — not only in the architecture of the Capitol Building, but in the enduring trees that frame its landscape. By cherishing and protecting these remarkable oaks, we ensure that their benefits and symbolism will inspire generations to come.