A key to sustainable Hawaiian agricultural production resides with the endemic sandalwood species

Progress report for GW20-211

Project Type: Graduate Student
Funds awarded in 2020: $24,997.00
Projected End Date: 07/31/2022
Host Institution Award ID: G181-21-W7902
Grant Recipient: University of Hawai'i
Region: Western
State: Hawaii
Graduate Student:
Major Professor:
Dr. Travis Idol
University of Hawaii
Major Professor:
Emily Thyroff
University of Hawai'i Mānoa
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Project Information


The economic and cultural values of Hawai‘i’s endemic sandalwood (Santalum) forest tree species can motivate large-scale sustainable agriculture through a silvicultural approach to restoration. Many forests in which sandalwood was once common were converted to livestock grazing or crop production and now a majority are abandoned with uncertain futures. However, reforesting suitable areas with sandalwood for timber production and oil distillation has emerged as a viable means to keep land in sustainable agriculture and diversify Hawai‘i’s agricultural products. Sandalwood is biologically and ecologically unique as a hemiparasitic tree requiring suitable hosts to survive. Sustainable sandalwood production, therefore, will require supporting diverse forest communities. The goal of our project is to improve the survival and establishment of planted sandalwood seedlings. The objectives are 1.) to better understand resource allocation between sandalwood and potential native host species and 2.) to evaluate the shade tolerance of planted sandalwood seedlings among already established host trees. Seedling survival, performance, and physiology will be measured to evaluate host suitability and sandalwood shade tolerance. Project success includes stronger partnerships with collaborating producers, as well as outputs both producers and researchers can utilize, including recommendations, scientific presentations and publications, K-12 lesson plans, and community outreach events. Outcomes include better understanding why certain native plants make more suitable hosts, how sandalwood host suitability and physiology in varying environments, increased confidence of land managers in establishing and managing diverse sandalwood forests, and greater awareness, knowledge, and appreciation of native Hawaiian species among students and communities. 

Project Objectives:

The overall goal of our project is to improve the survival and establishment of outplanted native ‘iliahi seedlings in order to support sustainable production. Successful propagation and planting are essential within the production cycle. Outcomes include understanding why certain native plants make better hosts, how ‘iliahi physiology responds under varying environments, increased confidence of land managers in establishing and managing diverse ‘iliahi forests, and greater awareness, knowledge, and appreciation of native Hawaiian species among communities.


Specific objectives are:

1.) Host plant suitability: to better understand resource allocation between ‘iliahi and potential native host species

2.) Underplanting ‘iliahi: to evaluate the shade tolerance of underplanted ‘iliahi seedlings among already established host trees


For both objectives, seedling survival, growth, biomass allocation, nutrient transfer, photosynthesis, and water potential will be measured to evaluate host suitability and shade tolerance of ‘iliahi. The objectives will be met by the leadership team members within the two-year project period (see timeline), with potential to continue monitoring the planted seedlings after the project has concluded with 5 and 10-year follow up measurements.


Please see the attached timeline document for proposed dates in order to accomplish both Objectives 1 and 2, as well as to accomplish outreach activities. Major activities are outlined and the month(s) highlighted indicate expected activity completion.



Click linked name(s) to expand/collapse or show everyone's info
  • Greg Hendrickson - Producer
  • Dr. Douglass Jacobs - Technical Advisor (Educator and Researcher)
  • Wade Lee - Producer
  • Steve McMinn - Producer
  • Tawn Speetjens - Producer


Materials and methods:

For Objective 2: Underplanting ʻIliahi, we planted ~1-year-old ʻiliahi, Santalum paniculatum, seedlings under 10-year-old established koa, Acacia koa during the wet season. The koa were originally planted on a grid so we planted the ʻiliahi on a offset grid to be between the koa trees.

At another underplanting site we planted ʻiliahi seedlings after thinning naturally regenerated koa. The koa were too dense and needed to be thinned. We marked potential koa crop trees and did a crown thinning (any koa that touched the crown of the crop tree was removed). After thinning we planted the ~1-year-old ʻiliahi seedlings during the wet season.

For both sites we cleared the competing vegetation mechanically with weedwackers. We cleared a weedwacker length radii around each seedling. We did this competition removal every three months for one year or until the ʻiliahi seedlings are primarily above the competing vegetation height.

We haven't been able to set up the Objective 1: Host Plant Suitability project yet, but intend to pair field ready host plants with 1-year-old ʻiliahi seedlings in the nursery this December 2021. 

Research results and discussion:

For Objective 2: Underplanting ʻIliahi, we had high establishment and survival success. At the first site, six months after planting we had 99% survival and seedlings on average increased their diameter by 1.1 mm and height by 4.1 cm. A potential emerging pattern with seedling diameter data is that intermediate koa canopy openness is resulting in greater diameter growth. It will be helpful to add additional data in August 2021 which is 1 year after planting. 

For the second site, four months after planting we had 98% survival. We will measure growth of seedlings six months after planting and also follow up on the growth measurements 1 year after planting.


Participation Summary
5 Farmers participating in research

Educational & Outreach Activities

1 Consultations
5 Curricula, factsheets or educational tools
3 On-farm demonstrations
1 Online trainings
3 Tours
2 Webinars / talks / presentations
3 Workshop field days

Participation Summary:

3 Farmers
2 Ag professionals participated
Education/outreach description:

The activites listed above ranged from working with the producers listed on the grant as well as local school groups from K-12 and home school groups. I also have interacted with a local hālau (traditional hula school) at my field sites. I contributed to an Earth Day video for public schools on island and I recently recorded videos at my field sites to share at a conference virtual field day tour and with a local non-profit for their outreach webiste. In the coming year I will be giving more presentations working on a journal article for Objective 2: Underplanting ʻIliahi. I will continue giving tours, hosting field days, and giving on-site demonstrations. With the new school year I have the opportunity to work with an AP Enviornmental class on a semester long project. I also presented on the underplanting project at Hawaiʻi Conservation Conference in July 2020.

Project Outcomes

2 Farmers reporting change in knowledge, attitudes, skills and/or awareness
1 Farmers intend/plan to change their practice(s)
2 Grants received that built upon this project
Did this project contribute to a larger project?:
1 New working collaboration
Project outcomes:

Having a better understanding of the regeneration component of ʻiliahi (Hawaiian sandalwood) is critical to having a sustainable product. Since the harvesting of ʻiliahi and distillation of its oil is destructive, we must conisder the regeneration of the plants after harvest. If we can ensure the harvest of ʻiliahi can be sustainable then future jobs and economy diversification can be done with more confidence. Harvesting from natural forests leads to additional ecosystem services for the environment leaving a better net result than other agricultural options.

Knowledge Gained:

Learning more about all the parts of the process from growing seedlings in the nursery to distilling timber has been illuminating. I am much more familiar with the nursery, planting sections, and initial harvest than the distillery work from prepping timber to the final product. Having a better knowlege of the whole process gives me greater appreciatation of the complexities of sustainable agricutlure and better understanding of where my skillset fits into the puzzle. There are many parts that make sustainabile agriculture work and I am glad I have been able to learn more about it.

Information Products

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.