The results presented in this WSU publication serve as a general guide for evaluating the feasibility of growing greenhouse seedless watermelon transplants, both non-grafted and grafted, as well as using grafted transplants to produce seedless watermelon in Washington as of 2014.
This publication is not intended to be a definitive guide to production practices, but is helpful in estimating the physical and financial requirements of comparable plantings. Transplants are grown by commercial nurseries, as well as some watermelon producers. Hence, the information and discussion presented are targeted to both commercial greenhouse transplant producers and watermelon producers who are considering grafting their own plants.
Specific budget assumptions were adopted for this study, but these may not fit every situation since production costs and returns vary across farm operations depending on the following factors:
- Capital, labor, and natural resources
- Crop yield
- Cultural practices
- Input prices
- Prices of transplants
- Management skills
- Size of the operation
- Type and size of greenhouse
Costs can also be calculated differently depending on the budget’s intended use. To avoid unwarranted conclusions for any particular operation, readers must closely examine the assumptions made in this study, and then adjust the costs and/or returns as appropriate for their operation.
Objectives of the Study
This study provides information on:
- The variable and fixed costs required to produce non-grafted seedless watermelon transplants in a greenhouse;
- The costs of producing grafted watermelon transplants in a greenhouse;
- The costs and returns of producing seedless watermelon in the field by using grafted transplants.
The data used in this publication are a composite of information gathered from experienced growers in Washington and Oregon who produce non-grafted watermelon transplants in a greenhouse. Their production practices and requirements for labor and capital are the basis for the budget assumptions used in this study and represent current production methods.
Information about supplies and labor associated with grafting watermelon plants are obtained from Lewis et al. (2014) and greenhouse studies at the WSU Mount Vernon Northwest Research and Extension Center. Data on crop yield resulting from field utilization of grafted transplants are obtained from field experiments in eastern Washington.
Greenhouse Production of Watermelon Transplants
In Washington, transplants are used for all commercial production of watermelon. Watermelon transplants are grown in a greenhouse, either by the grower (on-farm) or by a commercial propagator (off-farm). In some cases, the commercial propagation facilities are located near the farm; however, it is common for transplants to be shipped hundreds of miles across state boundaries.
Transplant production facilities vary greatly, but a typical design is a hoop-shaped greenhouse covered with polyethylene plastic and equipped with heaters and fans. Seeds are sown into 200-cell plastic trays by hand or machine, and then placed in the greenhouse, either on the ground or on benches. After emergence, the seedlings are regularly watered and fertilized for optimal growth.
The use of grafted watermelon plants is gaining popularity in the U.S. Although there are several grafting techniques available to propagators, only two—one cotyledon splice and hole insertion—are widely used on a commercial scale (Miles et al. 2013). The major challenge with these techniques is rootstock regrowth—the removal of which requires extra labor both in the greenhouse during transplant production and in the field during crop production.