Per the Duke Gardens website:
The Dawn Redwood has a unique history. In 1941, a Japanese paleobotanist named Dr. Shigeru Miki was studying fossils of ancient sequoias and bald cypresses found in Japan. He realized that some of the fossils had been incorrectly identified. Typically the sequoias and bald cypress have alternate leaves, while these mysterious fossils had opposite leaves. There were enough differences that he concluded these fossils were of a different genus altogether, and he named them Metasequoia – "meta" being Greek for "akin to"; thus "like Sequoia."
In the early 1940s, an unusual tree in the interior of China came to the attention of scientists in China's Central Office for Forestry Research. It was not until the spring of 1946 that Dr. Hu in Beijing realized that the living specimens and the Metasequoia fossils were the same tree. The Arnold Arboretum of Harvard University funded a seed-collecting expedition in mid-1947. The seeds arrived at the Arboretum in January 1948, and in 1949, the Sarah P. Duke Gardens planted one of the Arnold Arboretum's seedlings. Of the original seedlings, our Dawn Redwood is one of the larger specimens in the United States.
The base buttressing and exposed roots of our 1949 tree are unusual for Metasequoias. Because our tree is so striking, many people played, sat, and stood on the roots, often posing for photographs. These activities damaged the tree and now it is protected by a low chain fence. In the early 1960s, another Metasequoia seedling from the Arnold Arboretum was planted in the Rock Garden.