The azaleas in Seoul are blooming earlier than they used to, according to a report by Chang-Hoi Ho and colleagues in an upcoming issue of the International Journal of Climatology. This is one of those wonderful phenological studies in which researchers piece together a historical record of when plants flower, a relatively sensitive indicator of temperature trends. They used goldenbell, azalea, chery, peach and American locust.

Lilacs and honeysuckles have been used in North America, but the records here don’t go back as far as the Koreans’.