Development of Organic Production Practices for Pawpaw on Selected Rootstocks

Project Overview

Project Type: Research and Education
Funds awarded in 2003: $153,698.00
Projected End Date: 12/31/2007
Region: Southern
State: Kentucky
Principal Investigator:
Kirk Pomper
Kentucky State University

Annual Reports


  • Fruits: general tree fruits


  • Crop Production: conservation tillage
  • Education and Training: demonstration, display, extension, farmer to farmer, on-farm/ranch research
  • Farm Business Management: new enterprise development
  • Pest Management: biological control, flame, precision herbicide use
  • Production Systems: general crop production


    Pawpaw is a unique native tree fruit; however, there is little information concerning organic culture and methods to promote early fruit production available for this new crop. The objectives of this study were to determine: 1) the optimal orchard application rate of organically approved nitrogen to enhance pawpaw tree establishment and promote growth, 2) if flame cultivation can be used to control weeds/grass competition with trees compared to straw, woodchips or glyphosate application and the cost of each treatment, and 3) if seedling rootstocks derived from two cultivars (‘PA-Golden’ and ‘Sunflower’) would enhance tree survival, growth, and flowering of pawpaw cultivars. Organically approved (OMRI) nitrogen fertilizer was applied (0, 1, 2, 3, or 4 oz of N/tree) and growth and survival of seedlings examined. About 50% of trees in all treatments survived after one year, but by the fall of the second season only about 10% of the trees survived. This poor survival rate was likely due to the addition of N to plots promoting growth of grass and weeds in plots that also spread to control plots, high rainfall totals increasing weed competition, poor organic weed control (wood chip mulch), and a continuing problem of unknown causes for poor tree establishment rates in orchards. The rate of nitrogen required by pawpaw trees for optimum growth and survival was inconclusive; however, this experiment indicated the need for a holistic approach to tree establishment. Flame cultivation with a backpack flamer was effective in controlling grass/weed coverage around mature pawpaw trees without damage to trunk. Flame cultivation was found to be 2.5 times less expensive than straw mulch (organic) but 15 times more expensive than glyphosate (conventional) for grass/weed control. Several drawbacks of flame cultivation are that it uses fossil fuel for organic crop production and weed organic matter is lost for incorporation into the soil. Pawpaw chip-bud emergence was improved by leaving 6-8 leaves on the rootstock for 6 weeks after budding to support the scion budbreak and growth. None of the seedling rootstocks examined, ‘Sunflower’, ‘PA-Golden’, and ‘K8-2’, provided superior survival rates or earlier flowering of cultivars, and poor pawpaw tree establishment rates continue to be a challenge to growers. Over 20 grower workshops and five hands-on grafting demonstrations were conducted during the granting period.

    Project objectives:

    Objective 1. To determine the optimal application rate of organically approved nitrogen that enhances tree establishment, growth, early flowering, and fruit production in the orchard.

    Objective 2. To determine if flame cultivation can be used effectively compared to glyphosate (RoundUp) application for weed control to promote pawpaw tree establishment and growth in orchards.

    Objective 3. To determine if seedling rootstocks derived from two pawpaw cultivars (‘PA-Golden’ and ‘Sunflower’) will enhance tree survival, growth, flowering, fruit set, and fruit size of four pawpaw cultivars (PA-Golden, Sunflower, Shenandoah, and K8-2) compared to rootstock produced from commercially available mixed seed. Plantings for this objective will be established at six sites in three states (KY, VA and NC), including sites at KSU, UK, and four farms. All sites will serve as demonstration orchards in the future for pawpaw production for limited resource and organic farmers.

    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.