- Source: Endemic flora of the Chatham Islands
Although over 650 km (400 mi) from the main islands, the flora of the Chatham Islands is largely similar to the rest of New Zealand. About 400 of the 875 taxa (including hybrids) attested in the Chatham Islands are indigenous to them; of these, only 47 are endemic to the islands. The flora of the islands was described from samples in the mid-1800s by botanists Joseph Hooker and Ferdinand von Mueller, neither of whom ever visited the islands, while Leonard Cockayne provided the first comprehensive flora of the islands in the early 1900s. The islands have become highly noted for their flora and fauna, attracting ecotourists. One endemic, the Chatham Islands forget-me-not (Myosotidium hortensia) has become a botanical symbol of the islands due to its widespread cultivation in and outside New Zealand.
The endemic plants of the island are divided between taxa related to those on the North Island and those with stronger links to the South Island and the subantarctic islands of New Zealand. The archipelago comprise 40 islands and rocks. In addition to the larger islands of Chatham and Pitt Island, both endemic and introduced plants are found on various smaller islets. Coastal forests on the islands are dominated by indigenous and endemic trees such as Olearia traversiorum and Coprosma chatamica, with trees such as Dracophyllum arboreum further inland. In the wettest areas on the islands grow swamp forests of Coprosma propinqua and Olearia telmatica. Shore plants have a higher portion of naturalized species, often to the detriment of endemic flora. Although many of the endemic taxa are threatened due to naturalized flora and grazing by livestock, the populations of many species have rebounded since the 1980s due to widespread environmental regeneration practices. However, many taxa continue to be at risk, including three taxa listed as Nationally Critical by the New Zealand Threat Classification System (NZTCS).