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.^[1][2] The endemic plants of the islands 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.^[3][4] 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.^[5] 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.^[3][2]

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.^[3][4] 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.^[6] However, many taxa continue to be at risk, including three taxa listed as Nationally Critical by the New Zealand Threat Classification System (NZTCS).

Endemic vascular plants of the Chatham Islands

Scientific name	Image	Common name(s)	Family	NZTCS	Distribution	Ref.
Aciphylla dieffenbachii (F.Muell.) Kirk, 1899		Dieffenbach’s speargrass, soft speargrass, coxella	Apiaceae	Declining	Chatham, Pitt, Mangere, South East, small islets	[7][8]
Aciphylla traversii (F.Muell.) Hook.f., 1867		Chatham Island speargrass, taramea karupuru	Apiaceae	Declining	Chatham, Pitt	[9][10]
Asplenium chathamense Brownsey, 1985		Chatham Island spleenwort	Aspleniaceae	Naturally Uncommon	Chatham, Pitt, Mangere, South East, small islets	[11][12]
Astelia chathamica (Skottsb.) L.B.Moore, 1966		Chatham Islands kakaha, Moriori flax	Asteliaceae	Declining	Chatham, Pitt	[13][14]
Austroderia turbaria (Connor) N.P.Barker & H.P.Linder, 2010		Chatham Island toetoe	Asteraceae	Nationally Critical	Chatham, Pitt	[15][16]
Brachyglottis huntii (F. Muell.) B.Nord., 1978		Chatham Island Christmas tree, rautini	Asteraceae	Nationally Vulnerable	Chatham, Pitt	[17][18]
Callitriche chathamensis (R.Mason) Lansdown, 2022		Chatham Island starwort	Asteraceae	Naturally Uncommon	Chatham, Pitt	[19][20]
Carex chathamica Petrie, 1915		Chatham sedge	Cyperaceae	Naturally Uncommon	Chatham, Pitt, South East	[21][22]
Carex ventosa C.B.Clarke, 1906		Chatham Islands forest sedge	Cyperaceae	Naturally Uncommon	Chatham, Pitt, Mangere, South East, small islets	[23][24]
Coprosma chathamica Cockayne, 1901		Chatham Island karamū	Rubiaceae	Naturally Uncommon	Chatham, Pitt, South East	[25][26]
Copromosa propinqua var. martini W.R.B.Oliv., 1935		Tāpātāpā	Rubiaceae	Naturally Uncommon	Chatham, Pitt, South East	[27][28]
Corokia macrocarpa Kirk, 1899		Hokotaka, whakataka	Argophyllaceae	Naturally uncommon	Chatham, Pitt, Mangere, South East	[29][30]
Disphyma papillatum Chinnock, 1971		Chatham Island ice plant	Aizoaceae	Naturally uncommon	Chatham, Pitt, Mangere, South East, small islets	[31][32]
Dracophyllum arboreum Cockayne, 1901		Chatham Island grass tree, tarahinau	Ericaceae	Naturally Uncommon	Chatham, Pitt, South East	[33][34]
Festuca coxii (Petrie) Hack., 1906		Cox’s fescue	Poaceae	Naturally Uncommon	Chatham, Pitt, Mangere, South East, small islets	[35][36]
Geranium traversii Hook.f., 1867		Chatham Island geranium	Geraniaceae	Naturally Uncommon	Chatham, Pitt, Mangere, South East, small islets	[37][38]
Gentianella chathamica subsp. chathamica (Cheeseman) T.N.Ho & S.W.Liu, 1993		Chatham Island gentian	Gentianaceae	Naturally Uncommon	Chatham, Pitt	[39][40]
Leptecophylla robusta (Hook.f.) C.M.Weiller, 1999		Pouteretere	Ericaceae	Naturally Uncommon	Chatham, Pitt	[41][42]
Leptinella featherstonii F.Muell., 1864		Chatham Island button daisy, mutton bird plant	Asteraceae	Naturally Uncommon	Chatham, Pitt, Mangere, South East, small islets	[43][44]
Linum monogynum var. chathamicum Cockayne, 1902		Chatham Island linen flax	Linaceae	Nationally Critical	Chatham, Pitt, Mangere, South East	[45][46]
Macrolearia chathamica (Kirk) Saldivia, 2022		Keketerehe	Asteraceae	Declining	Chatham, Pitt, Mangere, South East, Little Mangere	[47][48]
Macrolearia semidentata (Decne. ex Hook.) Saldivia, 2022		Hangatere, Chatham Island aster, swamp aster	Asteraceae	Declining	(Chatham Islands)	[49][50]
Melicytus chathamicus (F.Muell.) Garn.-Jones, 1987		Inihina, hakina, hinahina, Chatham Island mahoe	Violaceae	Naturally Uncommon	Chatham, Pitt, Mangere, South East, small islets	[51][52]
Myosotidium hortensia (Decne.) Baill., 1890		Kopakopa, Chatham Island forget-me-not, kopukapuka	Boraginaceae	Declining	Chatham, Pitt, Mangere, South East, small islets	[53][54]
Myoporum semotum Heenan & de Lange, 2011		Chatham Islands myoporum	Scrophulariaceae	Declining	Chatham, Pitt, Mangere, South East	[55][56]
Myrsine coxii Cockayne, 1902		Swamp matipo, swamp mapou, Cox’s matipo	Primulaceae	Declining	Chatham, Pitt, South East	[57][58]
Olearia telmatica Heenan & de Lange, 2008		Shell akeake, swamp akeake	Asteraceae	Declining	Chatham, Pitt, South East	[59][60]
Olearia traversiorum (F.Muell.) Hook.f., 1867		Hakapiri, Chatham Island akeake	Asteraceae	Declining	Chatham, Pitt, South East, Mangere, small islets	[61][62][63]
Plagianthus regius subsp. chathamicus (Cockayne) de Lange, 2008		Chatham Island ribbonwood	Malvaceae	Declining	Chatham, Pitt, South East, Mangere, Little Mangere	[64][65]
Poa chathamica Petrie, 1902		Chatham Islands poa	Poaceae	Naturally Uncommon	Chatham, Pitt, South East, Mangere, small islets	[66][67]
Pseudopanax chathamicus Kirk, 1899		Hoho, Chatham Island lancewood	Araliaceae	Naturally Uncommon	(Chatham Islands)	[68][69]
Pterostylis silvicultrix (F.Muell.) D.L.Jones & M.A.Clem., 2002		Tutukiwi, Chatham Island greenhood	Orchidaceae	Naturally Uncommon	Chatham, Pitt, Mangere (possible)	[70][71]
Senecio radiolatus subsp. radiolatus F.Muell., 1864			Asteraceae	Naturally Uncommon	(Chatham Islands)	[72][73]
Sonchus grandifolius Kirk, 1894		Pūhā pārākau rahi, embergeria, Chatham Island sow thistle	Asteraceae	Recovering	Chatham, Pitt, Mangere, South East, small islets	[74][75]
Sporadanthus traversii (F.Muell.) Buchanan, 1875		Chatham Island bamboo rush	Restionaceae	Naturally Uncommon	Chatham	[76][77]
Veronica barkeri Cockayne, 1899		Barker’s koromiko, Chatham Island tree hebe	Plantaginaceae	Nationally Critical	Chatham, Pitt, South East	[78][79]
Veronica chathamica Buchanan, 1875		Chatham Island koromiko	Plantaginaceae	Naturally Uncommon	Chatham, Pitt, Mangere, South East, small islets	[80][81]
Veronica dieffenbachii Benth., 1846		Dieffenbach’s koromiko	Plantaginaceae	Naturally Uncommon	Chatham, Pitt, Mangere, South East	[82][83]

Endemic non-vascular flora of the Chatham Islands

Scientific name	Image	Common name(s)	Family	NZTCS	Distribution	Ref.
Lecanora kohu Printzen, Blanchon, Fryday & de Lange, 2017			Lecanoraceae	Data Deficient	(Chatham Islands)	[84]
Macromitrium longirostre var. ramsayae (Vitt) Fife, 2017			Orthotrichaceae	Naturally Uncommon	Chatham, Pitt	[85][86]
Sarcodia linearis (J.Agardh) Kylin, 1932			Gigartinales incertae sedis	Data Deficient	(Chatham Islands)	[87][88]
Ceramium chathamense G.Feldmann, 1950			Ceramiaceae	Data Deficient	(Chatham Islands)	[89][90]
Durvillaea chathamensis C.H.Hay, 1979			Durvillaeaceae	Naturally Uncommon	(Chatham Islands)	[91][92]
Gigartina grandifida J.Agardh, 1876			Gigartinaceae	Naturally Uncommon	(Chatham Islands)	[93][94]
Lessonia tholiformis C.H.Hay, 1989			Lessoniaceae	Naturally Uncommon	(Chatham Islands)	[95][96]
Landsburgia myricifolia J.Agardh, 1870			Lessoniaceae	Naturally Uncommon	(Chatham Islands)	[97][98]
Pyrophyllon cameronii (W.A.Nelson) W.A.Nelson, 2003			Erythrotrichiaceae	Naturally Uncommon	(Chatham Islands)	[99][100]