Arboretum in the City

The U.S. Capitol Grounds is a Level III-accredited arboretum recognized by ArbNet. This designation establishes the U.S. Capitol Grounds as one of 45 globally accredited arboreta that have at least 500 woody plant taxa, practice scientific research, promote conservation, and engage in public outreach and education to protect and preserve trees.

A team of professional arborists, urban foresters and plant health care specialists are responsible for the documentation and day-to-day care of over 4,800 trees and plants located throughout the 274-acre U.S. Capitol Grounds. This area includes lawns, parks, historic and commemorative trees, statuary, historic fountains and water features that provide an awe-inspiring setting for the U.S. Capitol.

The U.S. Capitol Grounds were designed by landscape architect Frederick Law Olmsted in a Capitol campus expansion project performed from 1874 to 1892. Olmsted used trees heavily in his design to both frame the building and provide shade for visitors. There are about 890 trees immediately surrounding the U.S. Capitol Building; approximately 40 of the original trees planted in 1874 remain on the grounds today.

An Olmsted original tree that is still on the U.S. Capitol Grounds; Members of the Capitol Grounds & Arboretum Tree Care Division plant a new tree along the North Drive sidewalk (left to right: Henry Brady, Harper Martin, Aaron Rowe and Steven Graham).

The work of the Capitol Grounds and Arboretum team is focused on preserving and improving Olmsted's legacy and the historical landscape. The Tree Care Division is a highly trained group of International Society of Arboriculture-certified arborists and licensed tree experts dedicated to the maintenance, documentation and overall care of the arboretum's woody plant collection. A team of arborists led by Steven Graham oversee tree health and risk assessment, tree planting, pruning, removals, emergency response, tree preservation, integrated pest management activities, and events such as memorial and commemorative tree planting ceremonies, and the Capitol Christmas Tree installation and lighting ceremony.

As part of routine maintenance around the Capitol campus, Melissa Westbrook, Capitol Grounds Urban Forester, and the arborist team use specialized tools to perform tree risk assessments. "We have several IML-RESI wood inspection drill systems that allow us to assess internal structural defects of trees that are not visible from the outside," said Westbrook. These tools, along with other technology such as sonic tomography (essentially using sound waves to create a tree X-ray), allow the arborists and the urban forester to assess decay and evaluate wood quality and stability. These are important tools for making informed decisions about tree risk and mitigating safety concerns on the Capitol campus.

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A Japanese pagoda tree removed for safety reasons in 2022.

The Tree Care Division is focused on preserving mature trees on campus and uses multiple evaluation tools to calculate ecosystem services and environmental benefits. Tree database software is used to develop an "eco-benefits" report of the arboretum's tree canopy to interpret cost savings the canopy provides due to storm-water runoff, carbon sequestration and cooling effects. "It literally pays to preserve our mature trees and do what we can to help them thrive in the landscape for as long as possible," said Westbrook. The team of arborists take their preservation role seriously and only prune or remove trees based on tree health and risk. Pruning is one component of maintaining tree health. The team follows industry best management practices for pruning to ensure things like proper cutting techniques are used to avoid exposure to potential diseases. Healthy trees contribute more clean air to the space around them and are less likely to be affected by weather events, pests and diseases.

"Trees are generally only removed if they pose an unacceptable level of risk to human safety or property that cannot be mitigated," said Westbrook. When a tree needs to be removed, the team follows sustainability practices that minimize waste to upcycle historical trees and limbs that are cut as part of tree maintenance on the U.S. Capitol Grounds. Over the past two years, Capitol Grounds and Arboretum has collaborated with the U.S. Capitol Visitor Center (CVC) Gift Shops, the District Department of Transportation (DDOT) Urban Forestry Division (UFD) and the U.S. Forest Service to help tell the story of urban wood utilization. Reuse of urban wood is a sustainable practice, supports a carbon-neutral policy, and gives new life to historical and significant trees in the arboretum's collections.

Joseph Wilkinson from Fredericksburg, Virginia, works with wood from the historic Japanese pagoda tree to create a bowl sold at the CVC Gift Shops.

When a tree needs to be removed, viable wood is given to U.S.-based wood artisans to create one-of-a-kind items for sale in the CVC Gift Shops and its online store. Each crafted item is part of the "Artisan Crafts from the Capitol Grounds Collection" and comes with a provenance card detailing information about the exact tree from which the item was crafted. Items currently in the collection include pens, decorative bowls, plates, gavels and jewelry. This collaboration allows the public to purchase a piece of historical trees from the U.S. Capitol Grounds.

"Once visitors discover that the wood product comes from the U.S. Capitol Grounds their face lights up and they begin to ask our Sales Associates questions about the Capitol Grounds and the trees planted on it," said Jamilah Charles, CVC Gift Shops Merchandise Manager. Visitors are excited at the opportunity of bringing home an item that it is meaningful and unique. The most popular items in the collection are the Japanese pagoda and red oak gavels. The gavels in particular are a popular item among the Capitol Hill community. The collection will be expanded this spring when wooden candleholders will be introduced. This partnership between the CVC and Capitol Grounds and Arboretum allows the Capitol Grounds team to salvage wood materials and provides opportunities to educate visitors about trees within the arboretum's living collection.

Olmsted's Japanese pagoda tree being milled by the District Department of Transportation Urban Forestry Division in Berryville, Virginia.

Another important sustainability initiative is the Capitol Grounds and Arboretum's urban wood reuse pilot program through the salvage of the Capitol Christmas Tree. This project, initiated in 2021, led to a collaboration that has allowed Capitol Grounds and Arboretum to transfer large, usable tree wood to DDOT UFD for sustainable reuse. After the end of the 2021 holiday season, arborists worked with DDOT to transfer the 70-foot Capitol Christmas Tree to their mill where the wood was repurposed into durable products such as tabletops and benches. The partnership allows DDOT to use wood from the Capitol Grounds in public school projects across the District of Columbia. Most recently, the 2022 Capitol Christmas Tree, a 78-foot-tall red spruce (Picea rubens) selected from the Pisgah National Forest, will be recycled to make musical instruments to be donated to local North Carolina communities.

More than 140 years after he envisioned it, Olmsted's design still drives all landscaping decisions at the U.S. Capitol Grounds. "We use Olmsted's design as the basis of our decisions since we have historic records that indicate which species and locations Olmsted used in his design," said Westbrook. In planting new trees, the Capitol Grounds team considers how the species contribute to the overall plant collections and genetic diversity in addition to the arboretum's goals of plant conservation and sustainability. The team evaluates trees for size, hardiness, susceptibility to insects and diseases and soil conditions. Careful tree selection is important to create an attractive and resilient landscape in the face of ongoing and emerging challenges. Maintaining healthy trees and sustainable landscapes requires consideration of how the landscape can support pollinators and beneficial invertebrate communities. These communities in turn provide natural pest control for potentially harmful tree pests. The placement and selection of new trees continues to follow Olmsted's plan for creating a natural and peaceful landscape in the nation's capital to be enjoyed and admired by visitors from all over the world.

Over the past five years, the Capitol Grounds and Arboretum team has used strategic tree planting initiatives to increase landscape function, resiliency and sustainability. These efforts have also reinforced the role the arboretum takes in managing urban forests to create landscapes that support the conservation of plant and animal species in urban ecosystems. The team is always working to expand their collaborative network among arboreta, public gardens and organizations committed to tree conservation, horticulture and collections management to protect and preserve the grounds for future generations.

Come visit the U.S. Capitol Grounds and enjoy an urban oasis in the nation's capital where the past and the future merge in the name of preservation.