The rare and threatened fern Christensenia aesculifolia of South-east Asia is listed in China as a second-ranked plant for national protection and is also categorized as one of 62 plant species with extremely small populations by the Yunnan provincial government. Field investigations during 2014-2017 failed to relocate one previously known population, and revealed that the single known extant population of C. aesculifolia contains only 10 individual plants. The most urgent conservation requirement for this species is to conserve the threatened habitat of the remnant population. Further field surveys and research are also required for an improved understanding of the species' status.