U.S. National Arboretum's deep roots

It's not easy being green. As the U.S. National Arboretum can attest, a lot of work and science goes into treating plant diseases, testing trees that can thrive in high-stress urban environments and controlling invasive plants at our borders. The arboretum, one of the world's leading horticultural science institutions, is credited with introducing more than 700 cultivated varieties of woody and herbaceous plants into the United States. With its gardens, paths and springtime azaleas, it's an urba...