Use of Cover Crops with Medicinal Herbs in North Hawaii

Project Overview

Project Type: Farmer/Rancher
Funds awarded in 2010: $20,117.00
Projected End Date: 12/31/2012
Region: Western
State: Hawaii
Principal Investigator:
Dr. Katherine Pomeroy
Kohala Medicinal Herb Farm

Annual Reports


  • Agronomic: oats
  • Additional Plants: herbs


  • Crop Production: cover crops, irrigation, organic fertilizers, tissue analysis
  • Education and Training: demonstration, extension, farmer to farmer, on-farm/ranch research, youth education, technical assistance
  • Farm Business Management: whole farm planning, new enterprise development, marketing management, value added
  • Pest Management: row covers (for pests)
  • Production Systems: agroecosystems, holistic management, organic agriculture
  • Soil Management: organic matter, soil analysis, soil chemistry
  • Sustainable Communities: leadership development, employment opportunities


    Three farms in the district of North Kohala, Hawaii Island planted test plots of five medicinal plants over a year long period as an on-farm trial of their objectives:

    1) determining optimum stress conditions,
    2) providing on-farm income, and
    3) training local youth.

    Extensive soil and plant data was collected and interpreted. Soil nutrient deficiencies were found in all the farms. Soil nutrient deficits are common in North Kohala due to the impacts of many decades as a sugar plantation. Curcumin, a medicinal constituent in turmeric, increased in the cover crop treatments in two of the three farms. This may be due to soil mining by the cover crop, by deficit irrigation conditions created by the cover crop and weeds or by another undetermined variable.

    Over a dozen youth were engaged in the process, with three of those involved throughout. Community outreach was conducted via events and local media, community groups, a farmer’s market day and the field day. While the project did not result in on-farm income, it did provide some ground-work for future development of income streams, such as the incorporation of health/agricultural tourism. This project also gave insight into what is involved with working cooperatively, with good results in terms of social relationships. The project was successful in raising community awareness regarding growing and using medicinal herbs.


    Three small farms (15-20 acres) located in North Kohala on the Island of Hawaii (20.1319 N, 155.7939 W) were planted with the same treatment plots. While the trials were set up to be as uniform as possible, a great deal of variation was inevitable. Although the farms are within five miles of each other, there is still a great deal of variation in rainfall and wind. The general area spans the northern tip of Hawaii Island, from windward to leeward, and all of the farms are located within two miles of the ocean at 400-600 feet elevation (see Figure 1).

    Our research question was based on the well-documented fact that wild-harvested plants are often more potent than cultivated plants in terms of medicinal chemical constituents. The reason for the higher potency found in wild-harvested plants is believed to be due in part to the more stressful growing conditions found in the wild than under commercial cultivation, and to the relatively larger amount of medicinal constituents often found in wild or traditional species (Biodiversity and the Ecosystem Approach in Agriculture, Forestry, and the fisheries Conference. Impacts of Cultivation and Gathering of Medicinal Plants on Biodiversity, Oct 2002, Rome). The project also builds on the concept of improving crop quality and chemical constituent levels by stressing plants during their growth cycle. Research has shown that deficit-irrigation treatments might be effective to increase the chemical constituency and/or quality of herbs and horticultural crops (Khalida et al., 2010; Lopes et al., 2011; Masmoudia et al., 2010; Oh et al., 2010; Palesea et al., 2010; Patan; et al., 2011; Pernice et al., 2010; Wang et al., 2010)

    Figure 1: Map of Hawaii Island and District of North Kohala

    Project objectives:

    The objectives of this project were to:

    1) Determine the optimum stress conditions for medicinal plant growth on five tropical medicinal plants (moringa, lemongrass, ashwaganda, turmeric and galangal ginger).

    2) Provide additional on-farm income for small, tropical family farms through the marketing of tropical medicinals.

    3) Provide local youth with inspiration and knowledge of sustainable agricultural practices through paid farm internships.

    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.