Hawaiʻi Grass ID Resources

Grass Atlas

Atlas of the geographical and elevation distributions of grasses found in Hawaii

Publications

Faccenda, K. (2024). From the Pasture to the Present: the History of Grass Introductions in Hawai‘i. [preprint].

Faccenda, K, Yorkston, M., Ross, M.C., Morden, C.W. (2024). Spontaneous hybridization among invasive Poaceae in Hawai‘i: Chloris × pseudosagrana nothosp. nov. and Cenchrus × peregrinus nothosp. nov. Phytotaxa 638 (2), 155-164.

Faccenda, K., Yorkston, M., Morden, C.W. (2024). Updates to the Hawaiian grass flora and selected keys to species: Part 3. Bishop Museum Occasional Papers, 156, 37-53.

Faccenda, K. (2023). Updates to the Hawaiian grass flora and selected keys to species: Part 2. Bishop Museum Occasional Papers, 155, 83-156.

Faccenda, K. (2022). Updates to the Hawaiian grass flora and selected keys to species: Part 1. Bishop Museum Occasional Papers, 148, 41-98.

Checklist

Hawaiʻi grass species checklist and island distribution. Now with common names, synonyms, and introduction mechanisms. PDF ONLINE EXCEL updated 2024.

New Identification Keys

Updated keys to Hawaiian grasses version 1.0 (2023-09-24)
New keys have been prepared for genera which have had multiple new state records found since 1990. These keys have largely been published in the publications listed below and are compiled into this document for ease of use. This will be updated periodically as keys for more genera are prepared.

Older Identification Keys

The keys in Wagner et. al (1990) "Manual of the Flowering Plants of Hawaii" published by the Bishop Museum is very out of date and is missing over 100 species which have been documented only over the past 30 years and I do not recommend it for keying invasive grasses to species. It is still a capable reference for native grasses, however. The key to genera should still work for most species and is recommended until a new key to genera is prepared.

The keys in Clayton & Snow (2010) "A Key to Pacific Grasses" published by The Royal Botanical Gardens, Kew should work for most other genera of grasses not covered by my updated keys. This book is, however, not easy to use. It contains only dichtotomous keys to species and contains no figures or descriptions of species making cross-referencing essential. I do not recomend it to anybody who is not already comfortable with grass identification.

In light of there not currently being any easy to use identification guides for Hawaiian grasses I highly recommend anybody interested in learning or identifying grasses post photos on iNaturalist. I am very active on that platform and review all grass photos posted from Hawaii. There is also a large library of reference photos there which I have helped to curate. Using this platform also allows the data to serve scientific functions; for example, I am actively using iNaturalist data for my own research into modeling Hawaiian Grass distributions.