The U.S. Capitol Building is surrounded by part of a collection of more than 4,800 trees spread throughout the entire 274-acre Capitol campus. Some of the trees are hundreds of years old; there is a Caucasian zelkova tree on Union Square from the Wilkes Exploring Expedition (1838-1842) that provided the U.S. Botanic Garden with its original plant collection. Most legacy trees on the U.S. Capitol Grounds date back to Frederick Law Olmsted's 1874 symmetrical landscape design, while other trees are quite young, and one has even been to the moon.

The Architect of the Capitol (AOC) has a special team of dedicated arborists from the Capitol Grounds and Arboretum jurisdiction that keep the trees on campus thriving. The team oversees tree health and risk assessment, planting, pruning, removal and preservation. They also have an important role supporting events such as memorial and commemorative tree planting ceremonies and the U.S. Capitol Christmas Tree installation and lighting ceremony.

To celebrate National Arborist Appreciation Day this month, we interviewed AOC arborist Matthew "Arnie" Arnold to learn more about his job with the team and their role preserving and improving Olmsted’s legacy and the historical landscape of the Capitol campus.

Q: Can you explain what an arborist does?

A: Arborists are woody plant experts. Anything that has to do with the care of trees or shrubs is in our wheelhouse. There are many different jobs an arborist can do, like pruning and removing, planting new trees or shrubs, treating plants for pests and diseases, completing an inventory on a plant collection, or performing risk assessments of hazardous trees. There are a lot of hats to wear in arboriculture, and all of them play an important role in preserving and maintaining healthy trees in our urban and suburban landscapes.

Q: What is the required education/training to become an arborist?

A: There are a lot of different pathways to becoming an arborist. One of the more typical paths is by working for a tree care company and following their progression from groundworker to climber to arborist, picking up the skills and knowledge you need from that experience. Another way is through scientific study. Obtaining a degree in a related field such as horticulture, forestry or ecology while studying topics related to arboriculture can be used to become an arborist too. Certain arborists will take on apprentices as well, literally showing someone the ropes. Once someone feels confident in their skills and knowledge and they have met some prerequisites, they can obtain certification from a variety of sources. Some states have their own tree care certifications, but the International Society of Arboriculture (ISA) sets the standard. Becoming an ISA Certified Arborist sets the stage for having a successful career in arboriculture.

AOC arborists complete routine tree pruning and removal when necessary. Usable wood from historic specimen trees is repurposed by local artisans into items sold in the U.S. Capitol Visitor Center gift shop.

Q: What are the challenges that you and/or your team face when maintaining the trees around campus?

A: The intersection of trees, safety and people is one of our biggest challenges. We work really hard to keep everyone safe while preserving the trees growing on Capitol Grounds and keeping them safe from people that work, visit and live nearby. We take extra care when pruning trees to keep people safe from falling branches by closing sidewalks and redirecting traffic whenever needed. We also have to balance what treatments are most appropriate for the trees on campus because while we would love to preserve historic trees, sometimes they pose a risk to the people that walk, drive or picnic beneath them. Completing our work in a safe manner and making sure that the trees themselves are not hazardous to our clients is incredibly important, but sometimes our clients can cause harm to the trees without realizing it. Walking in the areas below trees can cause compaction which makes it harder for tree roots to get the water and nutrients they need from the soil. Heavy machinery being used for projects and events on campus might hit a tree and cause a wound that weakens it. Tall trucks frequently hit and break the branches of street trees, causing a large wound and introducing disease. We have to balance the health of the trees with the intended use of the grounds to keep everyone safe.

Q: What is the best part of working with the Capitol Grounds and Arboretum arborist team?

A: I love that I get to work on so many unique trees in such a beautiful place. We're classified as a level III arboretum by ArbNet, an accreditation program created by the Morton Arboretum to acknowledge industry best practices, raise standards and to help arboreta across the world share information and promote conservation of woody plant species. Level IV is the highest level of accreditation, there are a lot of different requirements to achieve accreditation but part of it is the number of species, management practices and scientific initiative that exist in the arboretum. I'm proud I get to be a part of all of that and help create a beautiful place for some people to work and visit and hopefully learn a little bit about trees. It doesn't hurt that I get some incredible views of the Capitol Dome from the tree canopies too.

A swamp chestnut oak near the airshaft on the southwest side of the U.S. Capitol Building.

Q: Do you have a favorite tree on campus?

A: It's hard to choose just one, but lately one of my favorite trees on campus is the Swamp Chestnut Oak (Quercus michauxii) near the airshaft on the south side of the Capitol Building. It is a large, beautiful, capacious tree and its leaves turn an amazing scarlet red in the fall. It's native to the area and its relatively large acorns provide food for a variety of wildlife around campus. It's the perfect spot to relax in the shade and admire some of our other tree specimens.

Q: Can you share a special anecdote or memory from your work at the AOC?

A: I really enjoyed working with Kurato Fujimoto, a Japanese arborist that has been coming to areas of D.C. like the National Arboretum and Dumbarton Oaks to install traditional Japanese props to support old and culturally important trees. My coworker and fellow arborist, W. Harper Scott Martin, noticed his work around D.C. and reached out to see about getting his help to install tree support for some of our old cherry trees on the grounds, ones that we believe date back to the gift of cherry trees from the People of Japan in 1912, the same ones that line the Tidal Basin. It was very interesting to learn new techniques from an accomplished arborist and walk the grounds while the cherry blossoms were in full bloom. We are working to have this international expert revisit some of our trees in the future.

Capitol Grounds and Arboretum arborists undergo annual safety trainings, including precision felling techniques and high angle aerial rescue.

Q: What are some of the most important skills for an arborist?

A: I think the most important traits an arborist can have are being curious and hardworking. It is important to be curious because the tree care industry is constantly changing and evolving, and there is so much to learn about arboriculture. Different climbing techniques, new equipment and gear, tree biology, soil science, pesticide application, taxonomy, American National Standards Institute (ANSI) safe working practices, and tree identification are just a few of the topics important for an arborist to know. Striving to gain more knowledge and learn new skills and techniques makes an arborist safer, more efficient, and better at preserving healthy trees.

Q: In what ways can an arborist contribute to conservation efforts?

A: Arborists can contribute to conservation efforts in many different ways. The AOC's Capitol Grounds and Arboretum arborists work with other botanic institutions and conservation groups to target species of global conservation concern. Finding appropriate placement to grow these species on Capitol Grounds not only allows us to aid in global conservation efforts, but also grows our woody plant collections and allows for further public education about the importance of plant conservation. Arborists also educate the public about how to keep their trees healthy and keep them around longer, collecting wild seed to help grow trees for restoration projects, removing invasive species and doing our best to help maintain canopy to keep our streets shadier are all important ways to help. There are also volunteer opportunities to prune and maintain trees in places that need it but wouldn't get the right treatment otherwise. Anything we can do to keep a tree around is a good place to start.

Work safety zones are installed by AOC arborists to ensure staff and public safety during tree operations; Matt Rawson waters a newly planted tree in Senate Parks

Arnie and the rest of the Capitol Grounds and Arboretum team of arborists use strategic tree planting initiatives to increase landscape function, resiliency and sustainability. The AOC is always working to protect and preserve the U.S. Capitol Grounds for future generations.

Come visit, you may get lucky and witness an arborist at work while you appreciate the many trees on campus and enjoy an urban oasis in the nation's capital where the past and future merge in the name of preservation.


The gardens of the capital show all the hard work done.keep up the great work.

Great article - hope to visit one day!!! Arborists are artists in the trees that are overworked, underappreciated - yet continue the trade because of our deep passion for the benefits and beauty that these amazing living organisms provide!

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