Around the globe, biological scientists are racing to discover and document species before they are lost forever. The herbarium collection at National Tropical Botanical Garden contains nearly 90,000 preserved plant specimens, some dating back to 1837. It provides critical resources for biodiversity, ecological, and evolutionary research aimed at saving species. You can help us protect it. Donate to the Growing Green campaign today. Your gift will help us reach our energy efficiency goals and improve our Botanical Research Center to preserve this precious collection for generations to come.

It’s 2021 and scientists around the globe are working to document new species every day. It isn’t easy to believe in a world as connected as ours, but studies estimate that there are up to 15 million species living on Earth, only 2 million of which are known to science. This means we may share our planet, ecosystem, and maybe even our backyards with a multitude of unknown species!  

At current rates, it could take centuries for scientists to discover and describe life on our planet in its entirety. Even if it is possible to do so, biodiversity is declining and disappearing at rates not seen before in human history. Botanical gardens and scientific research institutions like NTBG have an essential role to play in making a difference and stemming the tide of extinction.

“Collections of pressed, dried, and accurately identified plant specimens (herbaria) are the foundation for all studies of plant diversity and evolution,” said David Lorence, Senior Research Botanist. “Like other natural history collections, herbaria are essential resources for the classification and the study of biodiversity. If we don’t know the names of species, we can’t conserve them,” he continued. 

“Collections of pressed, dried, and accurately identified plant specimens (herbaria) are the foundation for all studies of plant diversity and evolution.”

– David Lorence, NTBG Senior Research Botanist

NTBG Herbarium Collection

The Herbarium collection at NTBG includes:

• Native, cultivated, and invasive vascular plant species
• Bryophytes and lichens
• Marine algae and fungi

It is a unique reference of natural history and a resource for researchers at the National Tropical Botanical Garden and worldwide. The herbarium was established in 1971 as a record of the local flora when the Garden began operations. The collections have been built over more than 50 years through field expeditions and exchanges with other herbaria worldwide. NTBG has a very active collecting program adding 1-2 thousand new specimens per year, primarily from Hawaii and the Pacific.

As habitats disappear and our changing climate threatens all aspects of life on Earth, documenting biodiversity in herbarium collections will become increasingly important. So, how are plants entered into the permanent biological record? It starts with a discovery in the wild. 

Discovering New Species

When a new plant is discovered, NTBG scientists start describing the species and preparing it for preservation in the herbarium. Scientists take field notes on the habitat and surrounding vegetation, plot GPS points and collect, press, and dry the specimens. Photographs are taken to supplement the preserved specimens, and leaf material is obtained for later molecular phylogenetic studies using DNA.

The dried specimens from the field are freeze-fumigated to remove contaminants and pests before storage. Beetles and other insects can consume and destroy herbarium specimens if they are accidentally admitted into the collection. Once the new samples have been fumigated, they are mounted on archival paper with their labels, then barcoded, imaged, and incorporated into the NTBG collection. Duplicate labeled and identified specimens are shared with herbaria of collaborating institutions, including the country of origin where the species was discovered.   

Collecting Plants for Preservation Presents Challenges

Collecting plant material and entering a new species into the record is time-consuming and labor-intensive. It is often made more challenging by lack of funding, permitting, and regulations. 

“Successful fieldwork requires careful planning, funding, and collaboration, especially if it takes place outside the USA,” said Lorence. “First, it is important to establish contacts and partnerships with local organizations and individuals in the host country, for these are essential for obtaining access to collecting areas and collecting permits. Training and capacity building of host country partners is also an important aspect of fieldwork. We learn as much from them as they do from us,” he remarked.

Proper equipment is also an essential part of plant discovery and documentation. Native vegetation has disappeared from most lowland areas in the tropics, particularly on islands. Most intact native vegetation is confined to mountain slopes and summits, requiring strenuous hikes carrying collecting equipment, water, and supplies.

Flora of the Marquesas

Exploring and documenting the plant life of poorly known areas with herbarium specimens and making conservation recommendations are critical steps towards producing a region’s written flora. NTBG is dedicated to tropical plant discovery, research, and conservation and recently completed the Flora of the Marquesas, a collaboration between NTBG, the Smithsonian Institution, Délégation á la Recherche de la Polynésie Française, and others that was decades in the making. 

The two-volume book offers a complete account of all the plants found in the Marquesas. Of the 826 vascular plant species recorded, 331 species are native including 100 ferns and lycophytes, with the remainder being human-introduced. Nearly half of the native flora (47%) is endemic to the Marquesas.

“Knowing that specimens I’ve collected have contributed to a better understanding of the flora of a particular area is particularly gratifying.”

– Tim Flynn, NTBG Herbarium Curator

“Knowing that specimens I’ve collected have contributed to a better understanding of the flora of a particular area is particularly gratifying,” said Tim Flynn, NTBG Herbarium Curator. “The collections I’m making today aren’t necessarily for me or this time, but for future generations,” he concluded. 

Herbarium Collections like NTBG’s fill in the pages of the catalog of life on Earth and can help us respond to environmental changes and threats from habitat loss and climate change. Our collection is primarily comprised of plants of the Pacific, but many other research institutions and organizations are working to document and assess species on a global scale. 

A Global Catalogue of Life

The International Union for Conservation of Nature (IUCN) Red List of Threatened Species is the world’s most comprehensive inventory of the conservation status of biological species. It helps scientists evaluate the risk of extinction for thousands of known species of plants, animals, and fungi and is an essential tool for conservation management. On March 25, 2021, the IUCN released an updated Red List which includes 134,425 assessed species from around the world. 54,127 of them are plants, each given a rank in one of nine categories from species of “least concern” to “extinct.” 28 percent of the now assessed species are recognized as “threatened”. This recent update also includes assessments of all 255 Kauai single-island endemic vascular plants completed last year in an effort led by NTBG. By completing the Red List assessments for all of Kauai’s endemic plants, NTBG has verified that 10 percent are already extinct and the remaining 90 percent all classified as “threatened” according to the internationally recognized IUCN Red List criteria highlighting the scale and urgency of plant conservation in Hawaii. 

As a member of the IUCN Species Survival Commission for Hawaii, NTBG uses our Herbarium Collection data to assess the conservation status of Hawaii’s flora. Information about distribution range and population size over time determine if a species or taxon is considered a species of least concern, near threatened, threatened, endangered, or critically endangered. 

Digital Resources

NTBG Herbarium staff and volunteers are currently working on digitizing the collection. As of 2021, approximately 65% of the records have been digitized and made searchable online. 

NAPALI — Researchers with the National Tropical Botanical Garden were devastated when the last known wild member of the endemic flowering plant Hibiscadelphus woodii was found dead in the Kalalau Valley in 2011.

The plant only grows along the sheer cliffs of Kaua‘i and had only been discovered a few years earlier, in 1991, when new rope climbing techniques allowed for further exploration of the extremely rugged territory.

But, in 2016, the two more individual H. woodii plants were re-discovered using another new technology — drones.

Read the entire article at: https://www.thegardenisland.com/2021/04/19/hawaii-news/ntbg-completes-red-list-catalogue-of-endemic-plants/

April 18-24 is National Volunteer Week and at NTBG volunteers are critical to our success. Despite the suspension of the volunteer program in March 2020, volunteers returned in June and 294 individuals served nearly 11,000 hours! Volunteers enhance the visitor experience by greeting guests and offering interpretation in the garden. They help maintain our facilities, care for plants in the nursery and horticulture center, clean seeds to prepare them for storage, and mount and digitize specimens in the herbarium. These dedicated folks answer our numerous calls for support and lend their time, talent, and passion to assisting NTBG staff in documenting and protecting some of the world’s rarest plant species. As a nonprofit environmental organization committed to plant conservation, we rely on volunteers to help us save plants and people. You can help. Become a volunteer today or contribute to the Growing Green Campaign to help us reach our energy efficiency goals.

Spotlight on Botanical Research Center Volunteers

No matter your skill, age or interest, you can help National Tropical Botanical Garden save plants. This week we’d like to thank and highlight some of our dedicated Botanical Research Center volunteers. Find out what they are working on and what they love about volunteering with NTBG!

“Without our volunteers, we couldn’t accomplish many of our goals – we rely on volunteer efforts to mount almost all of our specimens as well as digitize those specimens once they have been mounted. These efforts help make our specimens available and useful to a world-wide audience. We simply couldn’t perform very necessary functions in a timely manner without volunteer help.”

– Tim Flynn, Curator of the Herbarium

Herbarium Specimen Mounting

Herbarium Specimen Mounting volunteers use their artistic eye to mount pressed and dried plant materials collected from the field onto paper for storage in the Herbarium. Sometimes this task can be quite challenging! Volunteer Joan Shaw had her work cut out for her carefully mounting this tiny challenge.

Herbarium Digital Imaging

Herbarium Digital Imaging volunteers have the important task of digitally documenting thousands of specimens collected by NTBG scientists. Digitizing the collection allows this unique reference of natural history and a resource for researchers searchable online. Specimens can also be found through JSTOR Plants database.

Seed Bank Assistant

Seed Bank Assistants help NTBG staff routinely check the viability of seeds stored in the bank. Seed banking is an important ex situ conservation means of rare and threatened flora and the NTBG Seed Bank and Laboratory currently includes over 15 million seeds representing 533 native Hawaiian taxa (892 total taxa, ecotypes and cultivars), which are routinely checked for viability.

Research Librarian 

The library collection at NTBG houses more than 20,000 books, journals, botanical prints, and archival materials.  With no librarian on staff, Lisa’s decades of experience in Library Science has been invaluable to maintaining this important collection.

On March 11, 2021, thick bands of heavy rain stretched across the Hawaiian Islands. While wet weather isn’t uncommon in the state this time of year, rainfall rates of more than 3 inches per hour certainly are. On the North Shore of Oahu, the storm caused catastrophic flooding and forced evacuations. On Maui, the intense rainfall washed out bridges, dams and damaged homes. On Kauai, landslides closed Kuhio highway in both directions at Hanalei; an area hit hard by the record-breaking rain bomb of 2018. All of the National Tropical Botanical Garden locations in Hawaii were closed, and some suffered damage to infrastructure and living collections. 

Unfortunately, this kind of story isn’t unique to Hawaii. The climate is changing all around the world. Climate models project that tropical regions worldwide will experience more significant swings in temperature and rainfall, prolonged droughts, and a more substantial threat from tropical storms and cyclones. 

How is Climate Change affecting the Hawaiian Islands, and What Can We Do?

“Climate change affects nearly every aspect of the human-natural ecosystems in the Hawaiian Islands,” says Dr. Uma Nagendra, Conservation Operations Manager and Ecologist at NTBG’s Limahuli Garden and Preserve. “Rising sea levels threaten roadways, houses, and coastal farmlands as well as endangered native lowland waterbirds. Increasing temperatures and droughts threaten local food security. On Kauai, we have seen firsthand how landslides, powerful storms, and wildfires can isolate and devastate entire communities and ecosystems,” she continued. 

“Climate change affects nearly every aspect of the human-natural ecosystems in the Hawaiian Islands”

In April 2018, a massive storm dropped 50 inches of rain in 24-hours on Kauai’s North Shore, setting a new U.S. rainfall record. Streams overflowed, homes and highways washed away, and many large-scale landslides buried vast swaths of forest, destroying native plant habitat. Cliffsides were left barren, and exposed soil offered an open invitation to invasive weeds that don’t provide the same ecosystem services as native forests because many fast-growing invasive plants are shallow-rooted, which can leave the landscape vulnerable to further erosion.

After this record-breaking event, NTBG scientists and conservation professionals returned to the field and the lab to apply ancient knowledge, new science and technology to save plants and continue to bring local and global climate solutions into focus.  

Learning from the Past 

“The most important lessons we can learn from the past are how to adapt and be resilient as the world changes,” says Dr. Nagendra. “Part of that is taking care of the ecosystems that sustain us with fresh water, stable land, and food. During the 2018 flood, we saw thousand-year-old structures withstand heavy flooding that infrastructure from the 1970s couldn’t handle,” she remarked.

To build resiliency and protect ecosystems from the unpredictability of climate change, threatened and endangered native plants must survive in botanical gardens and their natural habitats. The Limahuli Valley is the second most biodiverse valley in Hawaii, making it the ideal location for NTBG’s watershed-based conservation program at Limahuli Garden and Preserve. 

“The most important lessons we can learn from the past are how to adapt and be resilient as the world changes.”

The biocultural conservation program at NTBG’s Limahuli Garden collaborates with land stewards in the neighboring valleys to restore health and function to the social-ecological system that native Hawaiians have sustainably managed for more than 1,000 years. The ahupuaa system provides philosophies and practices for maintaining biodiversity, ensuring forest health, protecting stream integrity, creating fertile agricultural fields, promoting an abundant near-shore fishery from mauka to makai (mountain to ocean), and acknowledges that humans are part of the ecosystem. 

New Solutions Take Flight

National Tropical Botanical Garden has a long history of plant exploration and discovery. Nearly 90% of Hawaiian plants don’t grow anywhere else on Earth and are particularly susceptible to competition from invasive species and climate change because they evolved in isolation. Since the mid-1970s, NTBG botanists have navigated, climbed, and rappelled challenging terrain to hand-pollinate and collect material, including seeds, from rare plants. 

While NTBG botanists still work in the field, the addition of drone technology has allowed them to survey previously inaccessible areas and find new populations of rare plants – some thought to be already extinct in the wild. “In Hawaii, we are working as quickly as possible to collect, store and propagate rare plants in case suitable habitat disappears,” says Ben Nyberg, NTBG GIS specialist and drone pilot. “We are developing drone systems that can be applied by conservationists around the world to combat climate change in a number of ways, from survey to collection to reintroduction,” he continued. 

Documenting and collecting plant material is one step in the conservation process. Once rare plant populations are discovered and seeds collected, NTBG and partners must work together to store and propagate the plants safely. 

We are developing drone systems that can be applied by conservationists around the world to combat climate change in a number of ways, from survey to collection to reintroduction.”

Banking on Plants

Seed banking is a vital ex-situ or off-site conservation practice that helps protect plants from climate change, invasive species, and habitat loss. The NTBG Seed Bank and Laboratory currently store more than 15 million seeds from 533 native Hawaiian taxa. To store seeds wild-collected from native plants in the Limahuli preserve or remote cliffsides, seeds first must be meticulously cleaned to remove all fruit remnants. Once cleaned, information about when and where biologists collected the seed is recorded in NTBG databases, and research is conducted to determine if and how they can be stored long-term. 

“Back in the early 1990s, we thought that because of our geographic location in the tropics, seeds of most species would not be able to be conserved using conventional storage methods,” says Dustin Wolkis, NTBG Seed Bank and Laboratory Manager. “Thanks to our collaboration with the Hawaii Seed Bank Partnership and other institutions, we have been able to conduct long-term monitoring and have found exactly the opposite,” he noted. 

With more than 30 years of storage and viability data, NTBG and seed banking partner institutions can better understand trends and predict the storage behavior and viability of rare seeds giving new hope to many of Hawaii’s rare and endangered species. 

“Back in the early 1990s, we thought that because of our geographic location in the tropics, seeds of most species would not be able to be conserved using conventional storage methods. We have been able to conduct long-term monitoring and have found exactly the opposite.”

Bringing It All Together

At the intersection of ancient knowledge, new technology, and seed science sits an exciting new research project that could be a game-changer for Hawaii’s endangered plants. NTBG conservation staff at Limahuli Garden are currently investigating the use of drone technology as a means of revegetating landslide areas on Kauai. “The extreme rain and numerous landslides we have already seen on Kauai are exactly what we expect to see from climate change,” said Dr. Nagendra. “Conservation staff at Limahuli are working with Ben and the drone program to develop ways of using drones to distribute seeds and revegetate exposed soil with native plants after landslide events. We’re currently using seed trays to test the idea and see if it’s viable,” she continued. 

In addition to the possibility of revegetating with drones, ongoing research with DeLeaves and the University of Sherbrooke in Quebec is aimed at customizing drone sampling mechanisms to remotely collect plant material such as seeds or cuttings, and reach plant populations on steep or rocky cliffsides that have been largely unreachable. “Covid certainly delayed our field tests,” says Ben Nyberg, “but we have been able to collaborate and develop the robotics remotely.  Field trials have been scheduled for later this summer and we are excited to get to work.” 

Growing Green

Plants are one of our best defenses against our changing climate. They are the foundation of healthy ecosystems and can increase climate stability by offsetting temperature, moisture, and greenhouse gas fluctuations. From ancient knowledge to field surveys and seed storage, National Tropical Botanical Garden works at every level to discover solutions and save plants. You can help by. Visit our support page to see how you can get involved.

(March 25, 2021) Kauai, Hawaii — The International Union for Conservation of Nature (IUCN) updated the IUCN Red List of Threatened Species today. The IUCN Red List of Threatened Species is the world’s most comprehensive online source of information on the conservation status of the world’s plant, animal, and fungus species. Included in the updated list are 127 plant species unique to Kauai that were assessed in 2020. The effort was led by scientists at the National Tropical Botanical Garden (NTBG) and completes the assessment of all 255 Kauai single-island endemic vascular plants.

IUCN Red List assessments provide an essential tool for scientists and conservation managers around the world. By completing the Red List assessments for all of Kauai’s endemic plants, NTBG has verified that 5 percent are already extinct, another 5 percent are possibly extinct or extinct in the wild, with the remaining 90 percent classified as Threatened according to the internationally recognized IUCN Red List criteria. The majority of these were placed in the two highest categories: Critically Endangered (46 percent) or Endangered (41 percent), with only 3 percent assessed as Vulnerable.

At the same time, only 45 percent of these taxa are officially listed as Threatened or Endangered under the U.S. Endangered Species Act, demonstrating the importance of bringing Hawaii’s conservation challenge to national and international attention through the Red List.

The Hawaiian Islands are known for having one of the world’s highest rates of endemism (species found only in one specific location). Over millennia, adaptive radiation has led to the evolution of a highly diverse flora of more than 1,360 native plant species. Among the eight main Hawaiian Islands, Kauai has the highest level of endemism and diversity, in part because it is the oldest island.

However, Hawaii’s flora is threatened by invasive species, changing land use, and more extreme weather. It is estimated that at least 134 of Hawaii’s native plant species have gone extinct since the 1840s. With all of Kauai’s known endemic vascular plant species assessed for the IUCN Red list, the goal of assessing the endemic species across the Hawaiian Islands will help better evaluate threat risks and aid in the formulation of conservation strategies.  

Even as the assessment of Kauai’s endemic plants was underway, NTBG staff and its collaborators at the Department of Land and Natural Resources, Department of Fish and Wildlife, and the state of Hawaii’s Plant Extinction Prevention Program, made significant progress locating at least nine previously unknown populations of endangered native Hawaiian plants. Botanizing in rough terrain and remote locations, aided by helicopter transport and using drones and other new technology, NTBG discovered or re-discovered previously unknown plant populations in Kauai’s most challenging and inaccessible environments.

With today’s updated IUCN Red List, 134,425 species around the world have been assessed, 54,127 of them plants, each given a rank in one of nine categories from species of “least concern” to “extinct.” Twenty-eight (28%) percent of all now assessed species are recognized as Threatened.

The mission of the National Tropical Botanical Garden is to enrich life through discovery, scientific research, conservation, and education by perpetuating the survival of plants, ecosystems, and cultural knowledge of tropical regions.

Learn more about the work of the National Tropical Botanical Garden at ntbg.org. 

For media inquiries, contact: media@ntbg.org

On March 12, 2021, heavy rain caused flooding in Hawaii which affected all four of NTBG’s gardens in the state. For both Limahuli and Kahanu Gardens, the amount of rain was not unlike rain events that occur there on an infrequent basis, forcing the gardens’ closure but not creating significant damage. At Limahuli, the enhanced infrastructure installed after the 2018 flood functioned exactly as designed to divert water in a deliberate and calculated fashion.

However, for McBryde and Allerton Gardens on the South Shore of Kauai, the rain caused the worst flood event in more than 40 years. The Lawai Stream rose quickly and flowed swiftly, clogging every culvert with large trees and boulders. Water encroached into areas that had never experienced this type of deluge, including Big Valley and the Thanksgiving Room in Allerton Garden. Trees fell, sculptures and benches were displaced, and the Allerton footbridge was completely demolished and washed onto the beach.

This recent flooding in Hawaii tells us we cannot deny climate change any more than we can deny plant extinction. In the midst of uncertainty, we remain focused on our strategic priorities and embrace our mission of discovery, scientific research, and conservation of tropical plants and ecosystems.

Allerton Garden

McBryde Garden

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Plants are the basis of healthy ecosystems from ridge to reef across Hawaii. The islands have truly unique and diverse ecosystems that provide our communities with a myriad of critical resources.

However, our ecosystems are challenged with rapidly disappearing key native species as a result of invasive weeds, animals and diseases. A predicted changing climate is likely to bring more frequent and severe natural hazards. As stewards of the land, lets come together to protect our natural infrastructures and build resilience through nature-based solutions.

The Kauai Climate Change video series from NTBG’s Science and Conservation team, with support from the County of Kauai, provides a summary view of challenges from a changing climate in the context of the Aloha+ challenges, UN Sustainable Development Goals and Hawaii based Strategies for Plant Conservation.

By Charly Hotchkiss and Hayley Walcher, NTBG Conservation Nursery Team Members

When you think of invasive species on Kauai, you might think of feral cats predating on native birds, or Albizia trees growing from the coastline to mountain peaks, competing with native plants for space and resources. While invasive species are a huge problem in our wildlands, they also pose a threat here in our conservation nursery. Every day our team combats invasive garden pests of every kind. From invasive snail and slugs species to pests like ants and aphids that hitched a ride to Hawaii on alien plants and animals and have made a home here in the islands. Here are some of the most common garden pests we fight in the nursery and tips for protecting your home garden from them as well.  

Ants

Ants are an invasive species often overlooked. There are more than 45 species of ants that have been introduced to Hawaii and pose a threat to our work in the nursery in many ways. Ants reproduce in mass numbers and can cause root disturbance, farm other pest insects like aphids, create nests in hollow branches, twigs, and stems. They can be difficult to spot and are often noticed after damage has already been done. They create nests in potted plants and must be removed before plants can be sent for outplanting.

Rats

Rats were introduced to Hawaii when the Polynesian voyagers arrived. They were stowaways on the canoes that quickly reproduced and thrived. After the arrival of Captain Cook in 1778, other species of rats began to make Hawaii their home including the roof rat, Norway rat, and the common house mouse. All rats are omnivores and cause a plethora of issues in the plant conservation field, not just in Hawaii but worldwide. Rats will debark trees, eat native tree snails and slugs as well as native insects. The seeds of many native Hawaiian plants are a delicacy to rats. They eat new vegetative growth on plants in the nursery and treat our seed flats like a buffet. We put wire cages over most seed flats to protect them from these ravenous intruders. Bait stations are also strategically placed throughout the nursery. Both prevention methods not only use up our time, but cost money.

Lacewings

While most non-native species have a negative impact on our environment and our work in conservation, some can have positive effects. One such creature is the common lacewing. Not originally native to Hawaii, this beneficial insect is a treasure here in our nursery. They are members of the Chrysopidae family which includes 85+ genera all of which are predatory. Their alligator-like larvae are often referred to as “aphid lions” and for a good reason. The larvae can eat over 200 pest insects a week, their favorite being aphids, but they will also eat spider mites, caterpillars, etc.

We often find their eggs on the leaves of native Hibiscus plants here in our nursery. Mother lacewings almost always lay eggs on plants that are currently infested with pest insects, so when their babies are born, there is a feast awaiting them. However, this is a cycle we are able to manipulate in the nursery. When we find unhatched lacewings eggs, we can carefully move them to an area with a pest infestation we are currently battling. When the larvae hatch they are insatiable! By encouraging lacewing activity in the nursery we are able to cut back/limit the amount of pesticides we use to treat for pest insects and help create a healthy balance of pests and beneficial insects.

Tips For Combating Garden Pests in your Home Garden

Slugs. You can easily prevent slugs and snails through applying a bait pesticide labeled for home garden use and following the label instructions. However, if you would prefer the pesticide-free route, there are a few old gardener tricks that work well:

• Place shallow dishes of beer in the garden to attract and trap slugs and snails.
• Scatter eggshells in garden beds or around the base of plants. The sharp edges of the shells prevents snail movement. Meanwhile, as the eggshells break down they provide calcium to the soil.
• Baking soda can also be used as a deterrent on top of the soil or placed directly on the snail during dry weather. Baking soda is a salt and will work as such though like salt, it will not be effective when wet.
• Make newspaper tunnels. Snails and slugs prefer hiding and sleeping in dark narrow places. Take a newspaper and roll it into a “tunnel.” Fasten the edges with tape or paper clips and place in your garden near where slugs and snails frequent. Check your newspaper tunnel for slugs and snails in the morning.

Invasive plants. You can combat those pesky weeds with just a few simple tricks and vigilant weed pulling:

• Weed barrier cloths are a great start to a new garden bed or patch.
• Regularly mulching is helpful in preventing weeds and can be done without purchasing expensive mulch.  Use banana leaves or other “green waste” from your garden as mulch to not only buffer against weeds but also replenish your soil with nutrients.
• Planting native plants in your garden is also always a good idea. Choose natives specific to your area and densely plant them in areas you are trying to prevent unwanted weed growth.
• Dense planting in general is a good idea when battling against invasive plants. Borrow agroforestry techniques and densely crop together understory plants such as comfrey, mint, spinach, etc.

General Pests. A garden can be a sanctuary for us, but it can also look like a gourmet buffet to some pest. If multiple plants of one species are planted close together, this can create a “hot spot” for pests, kind of like a billboard saying “Hey, you like peppers, well there’s tons here!”

• Intercrop, or plant multiple species of plants together. Intercropping can confuse and deteriorate searching predators.
• Create a defensive border or intercrop with plants like Marigolds, citronella, lemongrass, verbena, and petunia. Plants like marigolds even release chemicals or smells that can actually deter nematodes away from an area.
• Attract beneficial insect predators with densely planted herbs. Basil, oregano, thyme, lavender, chives, rosemary, mints, catnip, lemon balm, onion, nasturtium, and most culinary herbs can all be densely planted and attract caterpillars, aphids, and mealybugs.

February is Invasive Species Awareness Month in Hawaii. As a biodiversity hotspot, much of Hawaii’s native flora is threatened by invasive species and has been in decline for years. Last year, a United Nations report from the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) documented the accelerating rate of species extinction worldwide with overwhelming evidence that ecosystem health is deteriorating faster than ever. 

With these stunning results in mind, there is no better time than now to learn about the threats Hawaii and tropical regions worldwide face from invasive species. Here are a few to be aware of in Hawaii and simple ways to get involved and help protect plants. 

What is an invasive species? 

Not all species introduced to a new place are detrimental to their environment. Invasive species are organisms that are not native to a particular ecosystem or region and cause environmental or economic harm to the area. Invasive species are often introduced with human assistance and are harmful to ecosystem health because they quickly adapt to their new environment and reproduce rapidly. Invasive plants, for example, can multiply swiftly and starve native plants of essential nutrients or resources. This results in the entire ecosystem being disrupted since other plants and animals (including humans) depend on native species for food, shelter, and clean water. 

Invasive Species in Hawaii

Plants and animals native to Hawaii are unique because of the archipelago’s isolated location. Many species that evolved across the islands did so without threats from predatory species and did not develop defense mechanisms like thorns or toxins meant to deter them. This is one of the reasons many native Hawaiian species can’t thrive when introduced species become invasive. 

Red Mangrove

Kauai is home to National Tropical Botanical Garden’s administrative headquarters, Botanical Research Center, Conservation Nursery, and three of our five botanical gardens. The Huleia River is a major waterway in the Nawiliwili watershed on Kauai with a long and significant history documented in Hawaiian stories and chants. Today, the river and surrounding wetlands face severe threats from an invasion of Red Mangrove (Rhizophora mangle). Malama Huleia is a nonprofit organization dedicated to removing invasive mangroves and reestablishing the native wetland ecosystem. By their evaluation, two miles of the riverbanks are 100% overgrown by red mangrove. The increasing mangrove density is threatening the habitat of at least five endemic waterbird species that are considered endangered due to habitat loss. 

Clearing the invasive mangrove from the river and surrounding wetlands isn’t just crucial for restoring habitat for endangered birds. It also provides an opportunity to replant appropriate native Hawaiian and Polynesian introduced plants. You can help Malama Huleia by volunteering and sharing their work. Monthly community workdays are scheduled on the second Saturday of every month from 8:00 a.m. until 12:00 p.m. Visit the Malama Huleia website for further details. 

Ungulates: Invasive Creatures Great and Small

Although fantastic, we’re not speaking of the PBS miniseries, but rather some of the most notorious and destructive invasive species in Hawaii. Ungulates or hoofed animals such as pigs, sheep, deer, and goats pose a significant threat to native plants in Hawaii. These hoofed animals can graze or uproot hundreds of plants in just one night and contribute to soil degradation and erosion. To protect our gardens and preserves, NTBG staff install and maintain miles of fencing to keep ungulates away from restoration sites. 

Feral pigs alone have been shown to contribute to habitat loss and endangerment of sixteen Hawaiian honeycreepers – small, colorful birds endemic to Hawaii. In partnership with several national and local experts in the field,  NTBG Science and Conservation staff contributed to the recently published research study of the effects of introduced ungulates (feral deer, goats, pigs) on native and alien plant species in the mesic forests of the Hawaiian island of Kauai.

Fungus Among Us

Ohia trees are the most abundant, ecologically important, and culturally significant plants in Hawai’i. They provide food and shelter for native animals and endangered forest birds, facilitate healthy soil development, aid in replenishing aquifers, and are prominent in many Hawaiian stories, songs, and chants. 

Nearly ten years ago, ohia trees on the Big Island of Hawaii began dying rapidly. Whole swaths of the forest seemed to wither and die overnight. In 2014, two species of invasive microscopic fungi were identified as the cause of Rapid Ohia Death (ROD). The deadly fungal spores spread easily through the air and invade ohia through broken branches or wounds in the trees. More than 135,000 acres of native forest on Hawaii Island have been affected, and in 2018, the fungal pathogens were also found on Kauai, Maui, and Oahu.   

Experts across the state of Hawaii have formulated a ROD strategic response plan. NTBG is part of the team collecting seeds and storing geographically and genetically diverse plant material that can act as a “genetic safety net” and help study resistance to the diseases. As of today, NTBG has 8,612,584 ohia seeds in storage. Staff and volunteers at the NTBG Seed Bank and Laboratory are conducting research and tracking data that will support ohia restoration efforts statewide.

There are five things every individual can do to protect ohia and prevent the spread of ROD in Hawaii:

1. Avoid injuring ʻōhiʻa.  
2. Don’t move ʻōhiʻa wood or ʻōhiʻa parts.
3. Don’t transport ʻōhiʻa inter-island.
4. Clean gear and tools, including shoes and clothes, before and after entering forests.
5. Wash the tires and undercarriage of your vehicle to remove all soil or mud.

Ornamental Invasives

Hawaii is a gardener’s paradise. Unfortunately, many plants introduced for their ornamental value have escaped from home gardens and become invasive in Hawaii. Plants in the Melastomataceae family often have beautiful flowers and foliage but can produce more than 1000 seeds per square meter and grow aggressively, crowding out and overshading native species. 

Miconia is one member of the Melastomataceae that is particularly aggressive and considered a noxious weed in Hawaii. Miconia are large trees that can grow up to 50 feet tall and produce large, oval-shaped, two-toned leaves. These plants are native to South and Central America and were introduced to Hawaii as a garden landscaping plant in the early 1960s.

Because Miconia trees can grow so tall and produce large leaves, they shade out native plants and can take over native native forests. The large leaves can also act as an ‘umbrella’ and reduce the amount of water that seeps into the watershed. Miconia also have a shallow root system which contributes to soil erosion and produces thousands of sand-grain sized seeds which are easily spread by birds, small animals and hikers. Miconia was introduced to Tahiti in the 1930s and has taken over two-thirds of native forest threatening 25% of native forest species with extinction.  

Landscaping your yard with native species is a great way to combat the spread of invasives and restore your local ecosystem. Native plants provide shelter for local birds and attract bugs and butterflies, which can be food sources for other native wildlife. Check with your local botanical garden and plant nurseries to see if purchasing natives is an option for your community. NTBG’s South Shore Gardens will host a plant sale on February 27, 2021. Shop for plants and meet experts that can help you plant native and keep Kauai safe. 

Invasive Species Lists and Resources

Preventing the spread of invasive species in Hawaii and protecting native ecosystems is vital to protecting and preserving biodiversity. For more information on invasive species in Hawaii and ways to get involved, visit the following resources:

• NTBG Science and Conservation
• Hawaii Invasive Species Council
• Hawaii Invasive Species Awareness Month Schedule of Virtual Events
• Kauai Invasive Species Committee
• Malama Huleia
• University of Hawaii College of Tropical Agriculture Rapid Ohia Death