From April 28, 2022 post.

On the eve of Arbor Day 2022, U.S. Senators Maggie Hassan and Jeanne Shaheen, and Representatives Annie Kuster (NH-02) and Chris Pappas (NH-01), dedicated a Black Gum tree on the Capitol grounds in honor of New Hampshire. 

“When Granite Staters and families from across America come to our nation’s capital, they get a true sense of the history and diversity of our country, including that of our natural environment,” said the New Hampshire delegation. “It is fitting that on the eve of Arbor Day a tree honoring the beauty of New Hampshire is added to this patriotic array. We are proud this tree from the oldest native species of our great state has a home here in Washington.”

Commemorative trees on the Capitol grounds, including state trees, honor various aspects of American history. Because the climate in Washington, D.C. is not suitable to the longevity of the White Birch, New Hampshire’s official state tree, a Black Gum tree was chosen to dedicate as New Hampshire’s commemorative tree on the Capitol grounds. The Black Gum is the oldest known living tree species in New Hampshire and the oldest deciduous hardwood throughout New England.

Original source can be found here.