By: Richard Quinn
Although small in size, the native Hawaiian garden at the IBM building, designed by HHF Planners, represents an important demonstration of the incorporation of a native ecosystem approach to the design and installation of an urban native Hawaiian landscape.
Until very recently, the existing landscapes of Waikīkī and urban Honolulu suffered from an almost complete lack of endemic native Hawaiian Plants. ‘Endemic’ refers to a plant native to Hawai‘i, and nowhere else. It’s ironic that the typical landscapes of Honolulu are comprised basically of the same small group of exotic tropical plants found at resort landscapes throughout the tropical and sub-tropical world. By using these exotic plants in our landscapes, we dumb down our sense of place and make Hawai‘i a bit less special. By using native endemic plants in our landscapes, such as koa and ‘ohi’a lehua, we celebrate the uniqueness of Hawai‘i, and help to preserve our bio-diversity.
So why aren’t there more of these native plants in our urban landscapes?
A simple answer is that for the most part, endemic native plants are not landscape plants. Endemic plants have evolved in Hawai‘i to have a mutual and synergistic relationship with other native plants and a specific native soil ecology, with a dependence on native fungus and soil bacteria to support the plant’s growth and health. Urban soils in Hawaii are no longer native, in the sense that they no longer contain the essential mix of microbes and biology needed to support Hawai’i’s endemic plants.
How do you create a native Hawaiian garden in urban Honolulu?
You start with an understanding of the components of native ecosystem biology, and take an ecosystem approach to landscaping, rather than trying to use native plants as substitutes for exotic plants in a non-native tropical landscape. To achieve this, it also means that the aesthetic goals need to shift as well, away from a manicured and colorful “tropical” look, to a more naturalistic and wild landscape.
This was our approach to the recent landscape renovation of the IBM Building in Honolulu, a small attempt at incorporating some elements of a natural ecosystem into an urban landscape. The garden has over 10 different species of native plants used in a relatively small area. The design was done in conjunction with Surface Design Inc, a California based landscape design company that oversaw the overall landscape and hardscape renovation design of the IBM Building. The landscape was installed, and is currently being maintained by, Takano Nakamura Landscaping. The Howard Hughes Corporation owns the IBM Building and is responsible for the recent building and landscape renovations. They have demonstrated a strong interest in the use of native and cultural plants at the IBM Building and in future landscaping for their Ward Center and Kaka‘ako properties.
Here are some of the aspects of this garden that make this landscape one with more of an ecosystem approach:
WATERING: Watering is done on a mixed schedule, with a deep watering (12 minutes) once per week, and a brief “shower” watering three times per week – keeping soil moisture levels constant is not beneficial to endemic native plants. Allowing the soil to slightly dry out between heavy waterings allows for deeper penetration of water by creating micro-fracturing of the soil structure caused by the fluxuation in moisture. Light watering between deep watering allows the ferns and other shallow rooted native plants to stay hydrated just enough to bridge to the next deep watering. This facilitates deeper root growth, plants that are conditioned to less watering, and better oxygen and moisture levels that are more conducive to beneficial soil microorganisms. This method of irrigation better mimics natural ecosystem processes and uses 50% less water than conventional watering schedules.
FERTILIZER: Fertilization should only be done to resolve very specific nutrient deficiencies, such as iron or manganese, based on soil tests or direct symptoms. Using typical high nitrogen and high phosphorus fertilizers in a native plant garden greatly decreases a native plant’s reliance on soil microbes, which thus reduces other benefits such as disease and insect resistance. At the IBM Building, we’ve stopped using conventional fertilization in the native garden, and instead we’ve used minimal application of humic acid (to promote micro-organisms), and an application of a palm fertilizer with micro nutrients of manganese, magnesium and iron (but no nitrogen or phosphorus).
ORGANICS: Leaf litter from native plants is important for the maintenance of the beneficial soil mycorrhizae and bacteria. Native plant leaf litter, such as the leaves of ‘ōhi‘a lehua and ferns, are slow to decompose, which is ideal for the native soil ecology and the formation of a humis layer. A coarse wood mulch should be re-applied about twice a year, or as needed to cover bare dirt areas. The native endemic plants of Hawai‘i seem to prefer a low nutrient soil, with a slow decomposition of organics and a slower nutrient cycling than the typical exotic plant landscape.
INNOCULATION: Still in progress, the idea is to introduce essential endomycorrhizal fungus and leaf endophytic fungi. This is being attempted by using leaf material and soil material from other native landscapes that presumably already have the needed micro-organisms present.
INSECTICIDES & HERBICIDES: As much as practical, only hand weeding is done in the native garden. The use of insecticides is carefully controlled, and only done in a very targeted way. Herbicides and insecticides can have an adverse effect on the soil ecology that is essential for the health of native plants. However, some insects, such as ants and snails, should be aggressively controlled. Ants are not part of the native ecosystem in Hawai‘i, and they can be responsible for the rapid cycling of nutrients as well as encouraging white fly, mealy bugs and scale insects. We strongly encourage the use of non-toxic baits and traps for control of ants and snails.
TRIMMING: The trimming of native plants should be avoided unless absolutely necessary (to remove dead or hazardous branches, and any dead Hala leaves). Do not trim or hedge native Hibiscus plants. The trimming of native Hibiscus can result in a flush of fresh new growth which is attractive to insects such as mealy bugs and white fly. Trimming can also be a source for the introduction of harmful plant pathogens and diseases. In creating a native Hawaiian garden, the intent is to resemble a more natural condition – not to be a manicured garden.
PLANT SELECTION: Plants have been chosen with an understanding of native plant mutualism. For example, the Palapalai ferns are very mycorrhizal and help to create a network of mycelium in the soil that helps the ‘ohia lehua trees. By providing a wide mix of a large number of different species of native plants close together, a more complete ecosystem is created. Native plants in a landscape should be thought of as cooperating together, versus competing, as they are linked together through soil microbes to form a larger organism.
Our hope is that this small native landscape at the IBM Building can act as an ongoing practical experiment in using theories on native Hawaiian ecology. It is expected that some plants will die, while others will thrive. Truly, a garden that will evolve into a successful example of an ecosystem approach to using native plants in urban landscapes.
Richard “Rick” Quinn, is a principal at HHF Planners and a landscape architect with over 30 years of design experience. Rick is well known for his extensive knowledge of tropical and subtropical landscape plants. He specializes in incorporating native Hawaiian plants into his design work, in the application of native ecosystem restoration and the utilization of an ecosystem approach to the use of native Hawaiian plants in urban areas.