First New Species of Temperate Conifer Tree Discovered in More Than a Decade

The Ulleungdo hemlock, found on a small Korean island, is likely already endangered, but it may hold the key to fighting invasive species.

By Gabe Popkin

PUBLISHED January 30, 2018

It's not every day—or even every decade—that a new species of conifer is found in the world's temperate forests. But late last year, researchers announced a new species of hemlock tree from Korea, proving that even our best-studied forests still hold surprises.

The new tree could help save one of its better-known cousins—a North American hemlock species being annihilated by a voracious insect. But the new find is so rare that it’s already being considered for an endangered-species listing itself.

“It’s probably the rarest woody plant in Korea, if not the world,” says Peter Del Tredici, a botanist at Harvard University’s Arnold Arboretum in Boston, who was on the team that discovered the tree.

Hemlocks—no relation to the carrot-family plant that killed Socrates—are large evergreen trees native to North America and eastern Asia. Their small, soft needles grow thick and lush, creating a sort of waterfall of green. In the rain-soaked forests of Oregon and Washington they can grow to 270 feet tall, but in most other places they top out well below 200.

Hemlocks often play critical ecological roles in the forest, harboring insects, spiders, and birds that don’t live on other trees. But in the eastern U.S., native hemlocks are succumbing to a Japanese insect called the hemlock woolly adelgid, which kills trees by sucking out their sap. The insect has mowed down stands of trees from Georgia to Massachusetts, and it is rapidly moving west and north into new areas.

Hidden in Plain Sight

Around a decade ago, then a Yale graduate student and now a U.S. Forest Service biologist, was studying Asian hemlocks’ genetics to understand why they can resist the adelgid when the Eastern hemlock can’t. He realized that DNA from a small group of hemlock trees at the Arnold Arboretum didn’t seem to match that of any known species. The trees had been labeled as southern Japanese hemlocks, but Havill was skeptical.

The arboretum’s records stated that the trees came from an island called Ulleungdo, about 80 miles east of the Korean peninsula. So Del Tredici traveled there in 2008 to collect leaves for further study. The tiny island, less than half the size of Washington, D.C., is basically the cone of a steep volcano rising out of the Sea of Japan.

“Everything is uphill on this island,” Del Tredici says. The hemlocks grow only in a few patches on the cone’s north slope, amid dense, humid forests of pine, maple, and beech trees.