Science & Conservation

Scientific research is fundamental to the mission of NTBG and to all aspects of our conservation, horticulture, and education programs.

The world’s plants and their habitats are disappearing at an alarming rate, many even before they have been named or studied. Through our research efforts, NTBG is participating in the global effort to establish a scientific basis for ecological conservation and develop methods for sustainable plant utilization that benefit people while protecting the environment.

The focus of our research is identifying, documenting, understanding, and conserving the rich diversity of plants and their habitats in the tropics, with particular emphasis on the plants of Hawai’i and the greater Pacific region. The results of NTBG research in systematics (classifying and naming biological organisms and studying their relationships to each other) and floristics (the study of the plants or flora of a defined geographic or political region) contribute important knowledge of the world’s inventory of plant species. In conjunction with systematics and floristics, staff research focuses on plant propagation, economic plants and ethnobotany, paleoecology, invasive species, phytogeography, pollination ecology, seed conservation biology, and restoration ecology.

Science and Conservation in Action

NTBG’s staff of highly trained scientists, researchers, biologists, and botanists work in the field, labs and nurseries to preserve and protect plants.

Areas of Research

Systematics and Taxonomy

Plant systematics is a science that includes and encompasses traditional taxonomy (classification and naming), with the additional goal of understanding the evolutionary relationships among plants.

A main focus of systematic research at NTBG is the primarily tropical Rubiaceae, or coffee family, the world’s fourth largest flowering plant family, with 13,500 species belonging to more than 600 genera. Various species produce alkaloids responsible for their economic and medicinal utility. An important research and conservation collection of Rubiaceae has been established at the NTBG. These living collections are important resources not only for systematic studies, but also are being investigated for activity of plant extracts on biological processes that adversely impact human health in collaboration with investigators from the International Center for Tropical Botany (ICTB) and Florida International University (FIU).

Pteridophytes (Ferns and fern allies)

Pteridophytes are important components of tropical plant communities and are another focus of systematic and floristic research at NTBG. This takes place through describing new species, writing floristic treatments, and via inter-institutional collaborations by sharing herbarium specimens and DNA samples collected by NTBG during the course of field work.


Phytogeography, the study of plant distributions, is built into all of the field work that NTBG conducts. Field researchers routinely map the distribution and abundance of rare Pacific island plants. Our herbarium (PTBG) houses all of this data through vouchered collections.

Pollination Ecology

Understanding plant breeding systems is a fundamental component of plant conservation, and the need for information is even more pressing for rare plants that have co-evolved with specialist pollinators that may also be rare or even extinct. For instance, if a plant species is incapable of full or partial autogamy (selfing), a total loss of reproductive output may be experienced with loss of a pollinator, so human assisted pollination may be one management practice to implement as a first step.

Our research focuses on understanding the pollination ecology of Hawaiian species to inform best management practices for the species outlined in the Hawaiʻi Strategy for Plant Conservation.

Seed Conservation Biology

In alignment with the Global Strategy For Plant Conservation, the Hawaii Strategy for Plant Conservation, and the National Seed Strategy we are investigating methods to preserve and protect Hawaiian species of conservation importance ex situ in the Seed Bank and Laboratory.

Our emphasis is determining seed and pollen storage behavior, seed longevity and aging kinetics, seed borne pathogen abatement, and seed dormancy and dormancy alleviation of native Hawaiian plant species of conservation importance. Our research aims to understand how seeds respond to desiccation and subfreezing temperatures, identifying regeneration intervals, and determining optimal seed propagation techniques.

Social-Ecological System Resilience

Social-Ecological System Resilience is the study of human-in-nature systems with the particular goal of understanding how these systems recover from unexpected, catastrophic change over time.

NTBG’s Limahuli Garden and Preserve is located within the most biodiverse eco-region in the Hawaiian archipelago and leads the coordination of research efforts in the social-ecological system (ahupua’a) of Haena. Key social-ecological system research components include history, ethnography, archaeology, forestry, agroforestry, botany, limnology, hydrology, sea bird and fisheries biology.


The culmination of floristic and systematic research of the plants of a particular region is the publication of its Flora. A Flora, when using the term to refer to a publication, is a book, online resource, or other work that describes the plant species occurring in a given area (either geographic or political) or time period. The purpose of a published Flora is to allow identification of the plants described in it and provide an historical record of these plants.

Led by Senior Research Scientist Dr. David Lorence and collaborators, NTBG has been conducting and floristic research across the Pacific for several decades culminating in the publication of several major regional Floras. A New Flora of Fiji, a substantial work of over 3,000 pages has been published, and a Chronicle and Flora of Niihau, which combines a flora with an historical account of this small island.

In 2020 a 2 volume book Flora of the Marquesas Islands was published and NTBG is currently completing the Flora of Samoa for publication in 2021. Continued fieldwork is conducted towards completing a Flora of Micronesia in the coming years. Several of the published and planned book Floras are preceded by online Floras. See more details about some of NTBG’s Flora projects below.

Flora of Marquesas Islands


The Flora of the Marquesas Islands is a collaborative project between the National Tropical Botanical Garden, Smithsonian Institution, and Délégation à la Recherche (Tahiti, French Polynesia). An internet-based Flora hosted by the Smithsonian Institution provides access to a database of specimens, plant images, checklists, island distributions, and literature. In addition to this Internet Flora, volume 1 of a two-volume book Flora has been published in 2019 and volume 2 in 2020.

Flora of Micronesia


Micronesia is comprised of some 4,500 small islands spread across a remote part of the western Pacific and is separated into six different countries. It encompasses an area comparable in size to the continental United States yet in total its combined land area comprises an area smaller than the state of Rhode Island.  Micronesia hosts an estimated 1,227 indigenous vascular plant species of which 365 are endemic to the region. NTBG and the Smithsonian Institution have published an internet-based Flora of Micronesia hosted by the Smithsonian Institution which provides access to a database of specimens, plant images, checklists, island distributions, and literature. A comprehensive written and illustrated Flora is currently being worked on for later publication.

Flora of the Cook Islands


The Cook Islands lie south of the Equator and form the westernmost part of East Polynesia and consist of 15 main islands and atolls, most of them inhabited. Until recently, however, the Cook Islands had no published Flora. Retired New Zealand botanist W. R. “Bill” Sykes authored a 973-page Flora of the Cook Islands which was published by NTBG in 2016. This milestone publication was funded by the International Association of Plant Taxonomists (IAPT) as a joint publication by NTBG, the Smithsonian Institution, Landcare Research, and IAPT.

Flora of Samoa


The islands of Samoa are a well-known biodiversity hotspot threatened by increasing population pressures and habitat loss, yet their Flora is poorly known compared to that of other Pacific archipelagos. Hawaiian Botanist W. Arthur Whistler (1944-2020) worked with the people and on the Flora of Samoa for nearly 50 years. Having worked with NTBG since the early 1970s, his collections of 4,900 flowering plant specimens are stored at the NTBG herbarium and form the foundation for the coming publication of the Flora of Samoa, Flowering Plants written by Whistler and edited by Lorence and Wagner. The Flora includes descriptions of 543 native flowering plants (including 11 new species), 33% only found in Samoa, and 290 naturalized flowering plant species. This book was published in 2022 and is available for purchase.

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