An Alpine plant on a volcanic island
On the highest slopes of Hallasan, a shield volcano that forms the bulk of Jeju Island, grows an unlikely survivor: a native Korean edelweiss, Leontopodium hallasanense. This plant is a close relative of the famous Alpine edelweiss, Leontopodium alpinum, known from the mountains of Europe. The Korean species thrives in the rocky alpine zone of the volcano, typically at altitudes above 1,700 meters (5,577 feet), near the summit of South Korea's tallest mountain.
Like its European cousin, Hallasan edelweiss is a member of the daisy family, Asteraceae. Its famous appearance comes from its modified leaves, not its true flowers, which are small and yellow in the center—but from the surrounding star-like, white modified leaves called bracts. These bracts and the plant's leaves are covered in dense, woolly hairs known as a tomentum. This white, felt-like coating is an important adaptation to the harsh mountain environment. It protects the plant from cold, aridity, and the intense ultraviolet radiation found at high elevations. The plant's Korean name, Som-Edelweiss (솜다리), translates to "cotton-footed," a nod to its fuzzy appearance.
A relict of the Ice Age
The existence of an edelweiss population on a relatively southern volcanic island is a puzzle of biogeography. Genetic analyses provide an answer, suggesting that Leontopodium hallasanense is a glacial relict. Its ancestors likely spread across the Korean peninsula during the Last Glacial Maximum, which peaked around 20,000 to 25,000 years ago. During this period, a colder climate allowed alpine and subarctic species to flourish at lower latitudes.
As the ice sheets retreated and the climate warmed, these cold-adapted plants followed the retreating chill. They moved northwards or, in mountainous regions, upwards in elevation. Hallasan, at 1,947 meters (6,388 feet), became a high-altitude refuge—a "sky island" where the cool, harsh conditions allowed the edelweiss to survive while populations in the warmer lowlands disappeared. The result is an isolated population, separated from its relatives in the mountains of mainland Asia and Europe. Genetic studies confirm this history, showing that the Hallasan edelweiss is more closely related to other Asian species of Leontopodium than to the European Alpine edelweiss. Today, this unique plant is a legally protected species within Hallasan National Park, a living record of the dramatic climate shifts of the Pleistocene.