Identification keys
GrassBase polyclave keys
Identify any grass online with an interactive polyclave key — worldwide or Hawaiʻi-specific scope.
Updated keys to Hawaiian grasses
Version 1.0 (2023-09-24). New keys for genera with multiple new state records since 1990, compiled from the publications below into one document.
Checklist
The most up-to-date checklist of Hawaiian grasses is part of the full Hawaiian flora checklist published November 2025 — more accurate than the Grass Atlas, which is nearly two years older.
Publications
- 2025Long delays in identification and publication of naturalized species: a case study of introduced grasses in HawaiʻiFaccenda K., Daehler C.C. · NeoBiota 99: 265–283
- 2025Updates to the Hawaiian grass flora: Part 4Faccenda K. · Bishop Museum Occasional Papers 163: 111–129
- 2024From the Pasture to the Present: the History of Grass Introductions in HawaiʻiFaccenda K. · Pacific Science 78(2): 165–200
- 2024Spontaneous hybridization among invasive Poaceae in Hawaiʻi: Chloris × pseudosagrana nothosp. nov. and Cenchrus × peregrinus nothosp. nov.Faccenda K., Yorkston M., Ross M.C., Morden C.W. · Phytotaxa 638(2): 155–164
- 2024Updates to the Hawaiian grass flora and selected keys to species: Part 3Faccenda K., Yorkston M., Morden C.W. · Bishop Museum Occasional Papers 156: 37–53
- 2023Updates to the Hawaiian grass flora and selected keys to species: Part 2Faccenda K. · Bishop Museum Occasional Papers 155: 83–156
- 2022Updates to the Hawaiian grass flora and selected keys to species: Part 1Faccenda K. · Bishop Museum Occasional Papers 148: 41–98
Research tools
Biodiversity Heritage Library search
Shows OCR text with passages matching your query highlighted, so you can tell at a glance whether a source is relevant. The BHL API is often slow — results can take a while.
Newspaper search
Works like the BHL search, but for historical newspapers: shows the OCR text with passages matching your query highlighted, so you can quickly judge whether an article is relevant.
GBIF synonym prevalence
Lists every synonym of a name with its GBIF occurrence count — handy for literature reviews and for knowing where to look in the herbarium.
Hawaiʻi climate maps
Average yearly rainfall and temperature across the islands. Data courtesy of the Hawaiʻi Climate Data Portal.
Older identification keys
The keys in Wagner et al. (1990), Manual of the Flowering Plants of Hawaiʻi, published by the Bishop Museum, are very out of date and miss over 100 species documented only in the past 30 years. I don't recommend them for keying invasive grasses to species. The manual is still a capable reference for native grasses, though, and its key to genera should work for most species until a new one is prepared.
The keys in Clayton & Snow (2010), A Key to Pacific Grasses, published by the Royal Botanic Gardens, Kew, should work for most genera not covered by my updated keys. The book is not easy to use: it contains only dichotomous keys, with no figures or species descriptions, so cross-referencing is essential. I don't recommend it to anyone not already comfortable with grass identification.
Historical documents
Introduction notebooks
University of Hawaiʻi introduction notebook. Original at UH Archives; files are organized as the physical books are.
Hawaiʻi Agricultural Experiment Station introduction notebook — names, quantity received, origin and dates for plants imported 1906–1966. Original at UH Archives. Clunky as a PDF since entries cross pages; I've digitized the grass entries, but I don't believe the full notebook has ever been put into a spreadsheet.
Floras & bulletins
- Hillebrand's classic 1888 flora — the first complete flora of the Hawaiian Islands. This version is higher resolution with much improved OCR compared to the low-quality copies online.
- Heller, A. A. 1897. Observations on the Ferns and Flowering Plants of the Hawaiian Islands. Minnesota Geol. and Nat. Hist. Survey Bull. 9 (Minn. Botanical Studies Vol. 1): 760–922.
- McClelland, C. K. 1915. Grasses and forage plants of Hawaiʻi. Hawaiʻi Agricultural Experiment Station Bulletin 36.
- Hitchcock, A. S. 1922. The grasses of Hawaiʻi. Bishop Museum Press, Honolulu. Hawaiʻi's first complete grass flora.
- Ripperton, J. C., Goff, R. A., Edwards, D. W. & Davis, W. C. 1933. Range grasses of Hawaii. Bulletin of the Hawaiʻi Experiment Station 65.
- Whitney, L. D., Hosaka, E. Y. & Ripperton, J. C. 1939. Grasses of the Hawaiian ranges. Bulletin of the Hawaiʻi Agricultural Experiment Station 82.
Hitchcock's travels
- A botanical trip to the Hawaiian Islands — a dialogue of Hitchcock's travels and notes.
- Explorations in the Hawaiian Islands — a one-page note briefly summarizing his travels.
- Floral aspects of the Hawaiian Islands — a detailed account of the ecosystems he observed.
- Botanical explorations in the Hawaiian Islands — an account of his travels with higher-quality scans of his photos.