• Topics: Horticultural Sciences  |  Olson, Steven M  | Freeman, Joshua H  | Watermelon 

Using In-Row Pollenizers for Seedless Watermelon Production¹

The popularity of seedless (triploid) watermelon has increased over the last decade. During peak watermelon production in the U.S. market in 2005 and 2006, seeded watermelons only comprised 22% of the market and averaged four to five cents less per pound (U.S. Department of Agriculture, 2005). When growers shift from seeded (diploid) watermelon production to seedless watermelon production, they must take into account that triploid (seedless) watermelon plants do not produce enough viable pollen to pollinate themselves (Maynard and Elmstrom, 1992). Hence, another source of pollen must be available to achieve acceptable levels of fruit set in the seedless crop. To achieve optimal seedless watermelon yields, 25% to 33% of the plants in the field should be diploid (seeded) (Olson et al., 2006; Fiachino and Walters, 2003; Nesmith and Duval, 2001). To ensure that the right number of plants are diploid, growers generally interplant a diploid cultivar in the same field to serve as a pollenizer, traditionally by using dedicated pollenizer rows. Typically, they plant every third or fourth row with a diploid cultivar. Generally the seeded and seedless watermelons are harvested separately unless rind patterns of the two are easily distinguishable. The use of diploid pollenizers in dedicated rows results in 67% to 75% of the watermelon plants per acre being triploid. It has now become difficult to market seeded watermelons, and few growers want to have a high percentage of their acreage in seeded watermelons. There are now dedicated pollenizer cultivars (commonly called special pollenizers) that are designed to be planted in-row with triploid plants. Commercially available pollenizers, their characteristics and sources are listed below (Table 1). The primary role of these cultivars is pollen production, and most do not produce marketable fruit. However, 'Jenny', 'Mickylee', 'Minipol', and 'Pinnacle' produce harvestable fruits.

At planting time, one crew punches holes and plants the field solidly with triploids. Then, another crew goes through the field and plants a pollenizer between every second and third or third and fourth plant. Here, the field contains 100% triploid plants. Most pollenizer cultivars are recommended to be planted at a 1:3 pollenizer to triploid ratio. This being the case, a pollenizer would be planted between every third and fourth plant within the row. Eliminating dedicated row space in the field for pollenizers increases the number of triploid plants and seedless watermelons harvested per acre. If a grower previously planted every third row with a pollenizer and then started using in-row pollenizers, their triploid plant population per acre would increase by 33% (Table 2). This fact must be taken into account when calculating input costs because triploid seed costs about three times more than diploid seed (Table 2).

Research at the University of Florida and Clemson University has been conducted comparing the effectiveness of seven in-row pollenizer cultivars based on seedless watermelon yields from plants pollenized by each cultivar. The following cultivars performed similarly and could all be expected to produce optimal seedless watermelon yields: 'Jenny', 'Mickylee', 'Patron', 'Pinnacle', 'Sidekick', and 'SP-1'. 'Minipol' was not tested but its growth habit is similar to 'Mickylee' and should perform comparably.

There are substantial differences in prices of pollenizers, so this must also be considered when choosing a cultivar. Most of the recommended cultivars can be easily distinguished from standard seedless watermelons (15-20 lbs) by their size, since most pollenizer fruit is small (Table 1). However, if a grower is producing mini or palm-sized seedless watermelons, a pollenizer with a distinctly different rind pattern must be chosen to avoid confusion during harvest. Most companies that produce triploid watermelon seed now produce pollenizer seed. If the pollenizers have been tested and found to perform well, it may be preferable for a grower to have a pollenizer and a triploid from the same company. Even though the pollenizers mentioned are effective, if a grower has a market for seeded watermelons, adoption of an in-row pollenizer may not be warranted.

References

Fiachino, D.C. and S.A. Walters. 2003. Influence of diploid pollenizer frequencies on triploid watermelon quality and yields. HortTechnology 13: 58-61.

Maynard, D.N. and G.W. Elmstrom. 1992. Triploid watermelon production practices and varieties. Acta Hort. 318: 169-173.

NeSmith, S. and J. Duval. 2001. Fruit set of triploid watermelon as a function of distance from a diploid pollenizer. HortScience 36(1): 60-61.

Olson, S.M., E. H. Simonne, D. N. Maynard, G. J. Hochmuth, C. S. Vavrina, W. M. Stall, T. A. Kucharek, S. E. Webb, T. G. Taylor, and S. A. Smith. 2004. Cucurbit production in Florida, p. 169-198. In: S. M. Olson and E. H. Simonne (eds.) Vegetable Production Handbook for Florida. Univ. Fla. Coop. Ext. Serv. and Vance Publishing. Lenexa, KS.

U.S. Department of Agriculture. 2005, 2006. National watermelon report. U.S. Dept. Agr. Agricultural Marketing Service. (http://www.ams.usda.gov) Thomasville, Ga.

Tables

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U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Millie Ferrer-Chancy, Interim Dean.

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