Hawaiian Plants
Na Lā’au Maoli
Metrosideros polymorpha (Ōhià) in Cultivation at Discovery Harbour, Hawaii
Photo © Edward Rau Use licensed CC BY-SA
Our research and development program is not focused on Hawaiian plants but we are engaged in several ongoing activities that support conservation and educational initiatives relating to these plants. These activities are described in this section. Some of the introductory content presented here was adapted from the Kàahahui Ò Ka Nāhelehele website. The organization’s mission is to advocate for the perpetuation of Hawaii’s dryland ecosystems, and the many often endangered plants, birds and insects that live within these communities
Additional information and references about the specific plants mentioned in this section will be available on the individual species listings in our Plant Information section, which is currently under construction.
For the forgoing discussion, it is important to understand terms relating to the origin and ecological status of Hawaiian plants. Please refer to our Website Glossary for definitions of terms as we use them on this website.
Introduction
Hawaii is one of the most biologically diverse regions on earth. Largely because of the geographic isolation and recent geologic formation of the islands, a large fauna and flora consisting of about 25,000 unique species developed here. About 90% of Hawaii’s native plants are found nowhere else in the world. The arrival of human colonists and the countless alien species they brought with them has devastated ecosystems and contributed to the extinction of many endemic plants. The native Hawaiian flora now includes some of the most endangered of all species; some plants populations consist of several plants or only single remaining individuals and are considered functionally extinct. Today, the rate of species extinction per unit of land area in Hawaii is probably the highest in the world.
Our limited work with Hawaiian plants has been with dryland forest species. The tropical dryland forests near our location are part of an ecoregion of Hawaii covering an area of 6,600 km2 (2,500 sq mi) on the leeward side of the main islands and the summits of smaller islands. These forests largely consist of plants that are adapted to dry conditions. Many are either deciduous in the dry season or sclerophyllous: with hard leaves, short distances between leaves along the stem (internodes) and leaf orientations parallel or oblique to direct sunlight).
Threats to the Dryland Forest Plants
The dryland forests once occupied a much larger land area in Hawai’i and supported a highly diverse biota with biodiversity significantly greater than that found in the wet windward regions of the islands. Land clearance, grazing, the introduction of many invasive animal and plant species, pests and diseases, increasing frequency and severity of wildfires, and other factors have decimated the forests and their biodiversity. The most important are contributors to the decline of the forests are:
Ungulates. The introduction of hoofed herbivores (ungulates) like pigs, goats, cattle and sheep has been particularly damaging to the dryland forests. Since the endemic Hawaiian plants evolved in the absence of ungulates they have few defenses against them, and feral ungulates lack predators to keep their populations in check.
Wildfires. Fire is another major and growing threat to the dryland forests and it is most associated with the presence of two highly invasive grass species. These are fountain grass (Pennisetum setaceum), an introduced ornamental grass and Guinea grass (Megathyrsus maximus var. maximus), introduced as a fodder. These fire-adapted African grass species have spread rapidly in and around the forests, displacing native plants. Their dried leaves provide abundant fuel loads that increase the frequency and intensity of wildfires, which are most devastating to native species. The fire-adapted alien grasses recover from fires much faster than native species, rapidly taking over the burned area and preventing regrowth of other plants.
Diseases. Ōhià (Metrosideros polymorpha), pictured above is an endemic tree species and comprises about 80% of the Hawaii’s forests. Recently, hundreds of thousands of the trees began to die off on Hawai’i Island from a disease now referred to as Rapid Ōhià Death (ROD). In 2014 Ceratocystus fimbriata, a fungal species or group of fungi, was identified as the causative agent of ROD. A quarantine rule is now in place prohibiting interisland movement of Ōhià plants and their plant parts. There is no treatment for trees affected by the disease and it is continuing to spread. As of early 2017 approximately 50,000 acres were affected. Refer to the Rapid Ohia Death website for additional information and updates on the status of the outbreak.
We believe that the fungi causing ROD may also pose a threat to several important crops in Hawaii such as coffee, eucalyptus, mangos and cacao. On Hawaii Island these crops are grown near Ōhià forests affected by ROD. Of special concern is the potential for transmission of the disease to coffee. In Indonesia and Central and South America the fungus causes coffee wilt and canker disease, which cannot be treated. The trees die and soils in the growing are contaminated. The disease is especially severe in Columbia and may make growing coffee in affected areas unprofitable. In 2015, we initiated efforts to improve awareness of coffee growers about the potential threat posed by ROD and about measures that they could take to reduce routes of disease transmission. Presentations were made at the Kàū Coffee Festival, Kàū Coffee College and other events, and an educational poster was prepared.
Introduced Pests. Rats, slugs, ants and other introduced invasive pest species have done enormous damage to native plant populations and resulted in the extinction of enemdic plant species in Hawaii. For the plants that we grow rats, and scale insects spread and tended by invasive ants have been the most damaging. No ants are endemic to the Hawaiian Islands.
Ant-tended Aphids on the Endangered Species Hibiscus kokio saintjohnianus (Kokiʻo ʻula)
Plant in cultivation at Discovery Harbour, Hawaii Photo © Edward Rau
Licensed use: CC BY-SA
These and other factors have resulted in severe fragmentation and degraded the dryland forests. Today most of dryland forests have been destroyed with only about five percent remaining, mostly as scattered remnants. Of these remaining forests, less than 3% are considered healthy.
Our Project Activities
Our work with Hawaiian plants primarily involves small scale production of some native plants for growing in artificial cultivation, identification and reporting of new invasive species, and assisting local organizations concerned with conservation of dryland forest plants.
Production of Native Plants for Artificial Cultivation
We believe that propagation and use of native plants in landscaping, for production as crops or intercropping with other plants of economic importance are becoming increasingly important ways to conserve vulnerable plant species and habitats. Most of the many factors causing the loss of dryland forests and endemic species in their native habitats will be difficult to reverse and are in fact worsening. While some dryland forest restoration projects are being carried in localized areas the work is labor intensive, largely dependent on volunteers and receives limited public funding. Artificial cultivation of native plants in the areas where they are endemic or outside these areas (ex-situ) has many potential benefits.
We have propagated several threatened and endangered native Hawaiian plant species, primarily for our research and educational purposes. Our experiences with some these are highlighted below and illustrate the challenges and benefits of growing these plants in artificial cultivation.
Hawaiian Gardenia (Nānū or Nāʻū)
The Hawaiian gardenia species Gardenia brighamii, also known as forest gardenia, was important to the native Hawaiians as a source of dye, its flowers were used in making lei and its hard wood was used for anvils for beating fibrous plant materials in production of kapa fabric.
This tree was once found on all the major islands and relatively common but it has been severely impacted by habitat loss, competition by invasive species and predation of its seeds by rats and insect pests. Today, it is critically endangered and extinct in the wild on Hawaii Island, Molokai and Maui. On the other islands, it is nearly extinct with only several individual plants remaining.
Nanu provides an extreme example of the conservation value of artificial propagation and cultivation. With appropriate care, it can be kept as an attractive hedge, specimen or landscaping tree and reproduced by cuttings, air layering or from seeds, if available. (Since seeds may be the products of from pollination by other introduced non-native gardenia species, it is uncertain if the seedlings are representative of the pure species or hybrids).
 Gardenia brighamii (Nāʻū) in Cultivation |
The plant is highly susceptible to multiple types of sucking insects, particularly scale insects (coccids) that are tended, and apparently spread by ants. If untreated these infestations severely weaken the plants and they may eventually die. In our area use of ant baits and treatment of the plants with a systemic insecticide such as imidocloprid is required to keep scale insects under control. Without these control efforts and artificial propagation by vegetative methods the species would likely have been lost.
 Ant-Tended Scale insects (coccids) on Gardenia brighamii |
Hawaiian Yellow Hibiscus (Maʻo hau hele)
 Flower of Hibiscus brakenridgei ssp. brakenridgei |
Maʻo hau hele, the native Hawaiian hibiscus species Hibiscus brackenridgei, is the Official State Flower of Hawaii. One of the two subspecies of this plant is now extinct and the other subspecies Hibiscus brackenridgei ssp. brackenridgei is now critically endangered. Wild populations are of the plant are declining rapidly and severely fragmented.
We are now producing some seeds and rooted cuttings of this subspecies from plants in sustainable cultivation. These may be used for landscaping purposes but not planted in the wild. Please refer to our new webpage on this species for additional information on the status of this plant and sales of seeds and cuttings.
Hawaiian Lo’ulu Palm
The Hawaiian palm species Pritchadia lanigera, also known by the common name of woolly loulu, and in the Hawaiian language as hāwane, or wāhane, noulu, or loulu (meaning ”umbrella”), is one of several palm species endemic to Hawaii Island. It was once relatively common over an unusual, large disjunct distribution at opposite ends of the Island. Today the palm is endangered, found only in eight subpopulations comprising less than 230 individuals. The absence of seedlings and juveniles at the known locations where the remaining trees are found in the wild suggests that regeneration is not occurring. Several factors are probably causing decline in this species: habitat destruction by wild pigs, and beetle, rat, and pig predation on the fruits, seeds, and seedlings.
Like the Hawaiian gardenia, we believe the prospects for successfully restoring wild populations of loulu are poor but it can be grown in cultivation if rigorous precautions for prevention and control of pests are maintained. While this palm is endemic to wetter conditions than are found at our site it is can be grown here in Discovery Harbour with drip irrigation and it is an attractive species for use in tropical landscaping. We currently have three specimens in cultivation, are protecting them from seed predators and hoping to produce seeds and seedlings. Fronds harvested from trimming the trees are donated and welcomed by Native Hawaiian organizations for use in educational presentations and crafts.
Banana Moth Infestation, Spring 2017
In April of 2017, during a period of severe drought, the tree in the photo below and two others became infested with banana moths Opogona sacchari (Bojer), perhaps the most important insect pest of Pritchardia palms in Hawaii. Drought conditions, wind damage, shallow soils and recent trimming may have stressed these trees, increasing susceptibility to moth infestations. These infestations progress rapidly, may be very difficult to control and can kill the trees. According to a local expert on palms, organic insecticides may not be effective. We are currently treating the affected trees with a combination of insecticides including foliar applications of neem oil and carbaryl, and soil drenches with a systemic insecticide (imidacloprid). Refer to the CTAHR publication for additional information on this subject.
 Pritchardia lanigera (Lo`ulu Palm) |
 Damage and Frass from Banana Moth Infestation of Lo`ulu palm (Pritchardia lanigera) |
 Banana Moth [(Opogona sacchari (Bojer)] Larva Feeding on Lo`ulu palm (Pritchardia lanigera) |
Ohai
Sesbania tomentosa (ohai) is an attractive endemic, leguminous shrub species that was once common and grew in dry areas at elevations below 2,500 feet (762 meters) on all the main islands of Hawai’i. It was probably present at or near our site in Discovery Harbour. Today, the species is endangered and nearly extinct in the wild on Hawaii Island. A few small remnant subpopulations still exist in the near the seashore area below our nursery. These areas are not accessible to grazing cattle but heavy, unregulated use of off road vehicles in the area has destroyed much of the habitat and decimated wild populations of the plant. The few remaining plants have reportedly enclosed in fencing to protect them.
Flower of Sesbania tomentosa (Ohai)
In cultivation at Discovery Harbour, Hawaii
Photo © Edward Rau
We were growing ohai plants from specimens obtained from the Amy B.H. Greenwell Ethnobotanical Garden. From these we produced 24 seedlings in our research greenhouse for donation to a restoration project at the Puuhonua o Hōnaunau National Historical Park and several small lots of seeds have been placed in secure storage at the Hawaii Islands Native Seed Bank.
Three specimens obtained from the botanical garden were outplanted here for study, seed production, and to observe their performance for potential use in landscaping. While we could grow them for about two years and obtain some seeds the plants eventually succumbed to attacks by multiple invasive pest species. Despite frequent monitoring for pests and treatment attempts, we were unable to save them without the use of systemic pesticides such as imidacloprid. (Neonicotinoid pesticides like imidacloprid could be toxic to endemic bee species feeding on the ohai flowers. Some of these bee species were recently listed as endangered species).
This outplanting experiment produced valuable information but illustrates the difficulties caused by invasive pest species in replanting endangered plants even in areas where they were previously endemic. The plants were affected by at least five pests at the same time: black stink bugs [Coptosoma xanthogramma (White)], aphids tended by ants, scale insects (Unaspis citri Comstock, identification unconfirmed), mealy bugs on roots and nematodes.
Pests of Ohai (Sesbania tomentosa)
 Stink Bugs (Coptosoma xanthogramma) Feeding on Ohai (Sesbania tomentosa) |
 Scale Insects (Unaspis citri? on Ohai (Sesbania tomentosa) |
 Mealy Bugs on Roots of Sesbania tomentosa (Ohai) |
 Nematode Damage on Decaying Ohai Roots |
Ho’awa
A previous owner of our nursery site planted a long hedge row of the Hawaiian tree species Pittosporum hosmeri, also known in Hawaiian as ‘a’awa, ‘a’awa hua kukui or ha’awa. The tree is endemic to our area and an excellent choice for landscaping uses because of its resistance to drought, wind and saline soils. The night blooming flowers of the tree also fill the air with a sweet fragrance.
Ho’awa (Pittosporum hosmeri) Planted as a Hedge
Photo © Edward Rau
Use Licensed under CC BY-NC
While not considered endangered, wild populations of ho’awa in our area appear to be in significant decline due to habitat destruction, competition with invasive Christmas berry trees, rodent predation of seeds, and the extinction of the Hawaiian crow (Corvus hawaiiensis) in the wild, which consumed and disbursed the tree’s seeds.
From seeds produced by our trees several hundred trees have been grown and donated or sold for planting on our island. It takes about three years to grow seedlings of a size suitable for planting and seed production varies significantly from year to year. This winter (2016) no seeds were produced. In the winter of 2015 an exceptionally high number of seed capsules were forming and we anticipated a large harvest. Unfortunately, we had to leave for a business trip to the mainland for two weeks. When we returned, we found that the entire crop (seeds, and even the immature capsule husks) had been consumed by rats! With few natural predators on the island rats are common and can do major damage to crops if control measures are not maintained continuously.
Destruction of Ho’awa Fruit (Capsules) by Rats
Rat Damage to Unripe Fruit of Ho’awa |
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Remains of of Ho’awa Tree Fruit |
Invasive Species: Preventing Invasions, Improving Awareness and Reporting
At Sustainable Bioresources we see the adverse impacts of invasive species every day and incorporate control activities into all our business operations:
- Not introducing new plant species in Hawaii unless they have been assessed for invasiveness and found to be of low risk, and we do not sell plants that are known to be invasive. These commitments are part of our Plant Pono Nursery Endorsement.
- Including information on invasiveness potential on our website for all plants that we have introduced in Hawaii or will sell.
- Providing information from our research to assist agencies in determining invasiveness potential.
- Reporting observations of plants and pests that appear to be new to our area.
New Invasive Species Reported
We have taken a leading role in reporting sightings of newly naturalized and potentially invasive plant species in our area of Hawaii Island. Below is information on two new invasive plant species that we reported to the Big Island Invasive Species Committee (BIISC). BIISC is a voluntary partnership of government, private and non-profit organizations, and concerned individuals working to address invasive species on the island of Hawaii. The identity of the plants reported was subsequently confirmed by specimens submitted by BIISC to the Bishop Museum and both were assessed by the Hawai‘i-Pacific Weed Risk Assessment (HPWRA) as high risk invasives.
Mickey Mouse Plant (Ochna)
In June of 2015 we observed a yellow flowered shrub emerging from the understory of Christmas berry trees in a vacant lot adjacent to our site. We tentatively identified it as an Ochna species. It was subsequently confirmed by the Bishop Museum as the South African species Ochna thomasiana Engl & Glig, commonly known as the Mickey Mouse plant or birds eye bush. Data compiled by Pacific Ecosystems at Risk (PIER) indicates that O. tomasiana was introduced and has become invasive on many islands of French Polynesia and most of the major Hawaiian islands. In Hawaii it is found in dry to moist mesic forests at elevations of 0-1000 feet (0-305 meters) on the Hawaiian islands of Kaua’i, Lāna’i, Maui and is widespread as an understory shrub in windward O’ahu. It was apparently not previously reported on Hawaii island. According to PIER another closely related African species Ochna serrulata (Hochst.) Walp. has escaped cultivation and become invasive on this island.
Members of the Ochna genus are popular ornamental plants and escape cultivation as their seeds are easily spread by birds and disposal of clippings. In New South Wales Australia ochna is a serious invasive pest and very difficult to eradicate because it sends out extended tap roots making even small seedlings difficult to pull out. Small pieces of root can reshoot. The Pittwater North Beaches Council has excellent materials on this subject and a video showing the labor-intensive techniques required to remove this plant. They look strikingly similar to those required for removal of Christmas berry trees here!
We are not aware of any control activities initiated since our original report. Plantings of Ochna spp. for landscaping uses at several commercial and residential sites have been found and we have noticed the emergence of ochna seedlings in disturbed soils on a vacant lot adjacent to us adjacent that was repeatedly treated with herbicides for weed control. It is unclear if O. tomasiana will persist here only as a naturalized plant in disturbed areas near habitations or if it will invade the dryland forest and compete successfully with the other dominant invasive species – Christmas berry and guinea grass.
Flower of Ochna tomasiana, a Newly Reported Invasive Species at Discovery Harbour, Hawaii
Photo © Edward Rau
Licensed use: CC BY-SA
Brazilian Pricklypear Cactus – First Reported Observation in Hawaii
In March 2016 we observed a group of very large tree like cacti growing in a dense ticket of Christmas berry (CB) trees on a vacant lot near our nursery. The observation was reported to the Big Island Invasive Species Committee who investigated and subsequently identified the cactus as the Brazilian pricklypear cactus, Brasiliopuntia brasilliensis (Willd.) A.Berger. According to the IUCN this neotropical species is endemic to Brazil and the Atlantic drainage eastwards of the Andes in Peru, Bolivia, northern Argentina and Paraguay. The Charles Darwin Foundation’s Galapagos Species Checklist indicates that it has been introduced in cultivation on Isabela, San Cristóbal, Santa Cruz islands in the Galapagos but is not naturalized there. In some other areas where it has been introduced it has become naturalized. In the U.S. it has naturalized in Florida. No previous reports of occurrences in Hawaii were found.
 Brazilian Pricklypear Tree Cactus (Brasiliopuntia brasiliensis) |
 Rooted Cutting of Brazilian Pricklypear Tree Cactus (Brasiliopuntia brasiliensis) |
Observations of this cactus at the location in Discovery Harbor where it is growing suggest a high potential for invasiveness:
- The plants location are growing from cactus pads that are dropped on the ground under Christmasberry(CB) trees and the mature plants are growing up through and above the maximum height of these trees.
- The cactus is apparently tolerant of the shading and adverse soil conditions associated with CB roots. Perhaps the plants have evolved with adaptations allowing them to grow together since the natural ranges of the cactus and CB overlap in South America.
- Leaf pads and cuttings potted in soils from this area root quickly, grow rapidly and produce numerous pads.
- Cactus growing adjacent to the road is cut and chopped up by brush clearing equipment operated by county road maintenance crews. Large amounts of viable cuttings are generated by this process. These fall to the ground or are transported to other distant locations for disposal potentially spreading to new areas.
- The cactus blooms frequently and has set fruit containing seeds.
- After our report this species was assessed by the Hawaii-Pacific Weed Assessment (HPWRA) system and has been assigned a score of 7, indicating high potential risk of invasiveness.
Collaboration with Local Organizations
We work with and support other local organizations the concerned with dryland forest conservation such as such as Ho`omalu Ka`ū, the Hawaii Islands Land Trust and Hawaii Nature Conservancy. Here in the K’au District resources are very limited so it is particularly important to share and leverage what we have in collaborative projects. Our support activities have included assisting with presentations, workshops and displays, providing plants for fundraising, and specimen materials for educational purposes.
Currently, we most engaged with Ho`omalu Ka`ū as it is the only organization focused on dryland forest plants in our area. We have worked with them to provide a series of educational workshops for the public, provided live plant materials for displays, plants for their sales and other fund raisers, website space and are assisting distribution of their booklet. Please click here for more information about the organization and our collaborative projects with them
Screening Native Plants for Medicinal Compounds
Many medicinal uses of endemic, indigenous and especially Polynesian introduced plants were described by Native Hawaiians. These plants could be sources of important new drug discoveries but the loss of ethnobotanical knowledge, lack of research and the accelerating extinction of endemic Hawaiian plant species presents serious obstacles to making such discoveries.
Knowledge of how to gather, use, prepare and administer medicinal plants was held by herbalist-physicians known as the kahuna lāàu lapa àu. This knowledge was passed from elder male experts to the next generation apparently through a long period of one-on-one training beginning at an early age. There was no written language. With the arrival of the Europeans and their incurable diseases many of these healers may have perished and their practices were largely replaced by Western medicine. Today, it is doubtful that many new herbalist-healers are being trained. Much of the ethnobotanical knowledge of the kahuna lāàu lapa àu may be lost and few compilations of this knowledge exist.
Drug Screening. Many endemic Hawaiian plant species have not been screened to determine if they have potential uses as drugs. We have provided the College of Pharmacy at the University of Hawaii in Hilo with specimen materials from our cultivated endemic Hawaiian plants such as Pittosporum hosmeri (hoawa) and the Hawaiian prickly poppy, Argemone glauca (pua kala) for preliminary screening for antimicrobial and antineoplastic activity.
Pictured below are the flower heads of shampoo ginger (Zingiber zerumbent), also known in Hawaii as “awapuhi”. It is an example of a canoe plant – one brought to the Hawaiian Islands by the first Polynesian settlers. In early Hawaii it was used in various forms as a medicine for treatment of indigestion, headache, sprains, sores and other ailments. Today researchers are investigating potential uses of extracts from the plant in treating several diseases, including some of great contemporary importance like cancer and diabetes. As of April 2017 research involving the plant was published in over 120 scientific papers found on PubMed.
Flowers Heads of Awapuhi or Shampoo Ginger Zingiber zerumbet
In cultivation at Discovery Harbour, Hawaii
Photo © Edward Rau
For additional information on Hawaiian plants, their propagation and medicinal uses we recommend these publications:
Recommended References
Abbott IA. 1992. Laàu Hawai’i. Traditional Hawaiian uses of plants. Honolulu (HI): Bishop Museum Press.
Gustafson RJ, Herbst DR, Rundel PW. 2014. Hawaiian plant life. Vegetation and flora. Honolulu (HI): University of Hawai’i Press.
Gutmanis j. 2013. Hawaiian herbal medicine. Second edition. Honolulu (HI): Island Heritage Publishing.
Liieeng-Rosenberger KE. 2005. Growing Hawai’i’s native plants. A simple step-by-step approach for every species. Honolulu (HI): Mutual Publishing, LLC.
Native plants Hawaii. c2009. University of Hawaii. Native plants Hawaii. http://nativeplants.hawaii.edu/index/ [accessed 2017 Apr 10].