Over the past ten years, evaluating dozens of watermelon and melon cultivars each season has allowed me to explore many unique types that differ from those typically found in mainstream markets. Some of these melons stand out with their distinctive rind patterns, varied colors, exceptional flavors, or other special characteristics. I’ve shared my observations through experimental reports and various presentations, hoping to spark curiosity among growers and consumers alike. Whether or not those reports played a direct role, it’s been exciting to watch some of these unique melons gradually gain traction. I’ve seen varieties I once trialed appear in seed catalogs used by direct-market growers, show up at farmers markets, and—most excitingly—make their way into my local chain grocery stores.
For specialty melons, refer to this article Cantaloupe and Specialty Melon Variety Evaluation in Indiana.
In this article, I would like to share a recent effort to grow a personal-sized, seedless watermelon with exceptionally thin rinds in a high tunnel. In previous open-field variety trials, we identified watermelon cultivars with this desirable thin-rind trait. While this trait may increase the fruit’s vulnerability to hail, heavy rainfall, and damage during handling and shipping, it also offers clear consumer advantages. Thin-rind watermelons tend to have a higher proportion of edible flesh and produce less waste. Some of the identified cultivars also showed higher sugar content and relatively softer flesh, a combination that may appeal to consumers seeking superior flavor and eating quality.
Although we have successfully grown those cultivars in the open field, using protected structures may help mitigate the risks associated with their delicate rinds, while offering additional advantages of protected production. Growing watermelons in protected environments, such as high tunnels or caterpillar tunnels, is relatively uncommon in the U.S., but it is a well-established practice in many Asian countries, where low-tech tunnels are used to produce premium-quality fruit.
An immediate challenge for this production system is pollination. A key consideration is the choice of pollenizer plant. Pollenizer watermelon plants are crucial for seedless watermelon production, as they provide the viable pollen necessary for fruit set. Pollenizer plants are typically interplanted with seedless watermelon plants to ensure adequate pollination. In large-scale seedless watermelon production, pollenizer plants that produce non-edible fruit are commonly used, and are usually planted at a 1:3 ratio (pollenizer to seedless). Increasingly, seeded watermelon cultivars with fruit that are easily distinguishable from seedless types are used as pollenizers.
In this trial, we evaluated two types of pollenizers for seedless watermelon production: a non-edible pollenizer plant and a yellow-rind seeded watermelon cultivar. The results were promising. Without the addition of bee hives, a 30-foot by 90-foot high tunnel could produce up to 432 seedless watermelons when the non-edible pollenizer was used. In comparison, using the seeded watermelon cultivar as the pollenizer resulted in approximately 244 seedless and 72 seeded watermelons. The yields were comparable to those typically seen in open-field production, and potentially higher yields may be achieved by increasing plant density.
This system required minimal management, with vines grown directly on the ground. Watermelons produced in the tunnel experienced lower foliar disease pressure and had excellent field-holding capacity. These advantages suggest that tunnel-grown watermelons can be cultivated with little pesticide use and low labor requirements. When combined with unique cultivars, this system may present a new opportunity for the direct-to-consumer market.
Detailed information about this experiment can be found in the experimental report Evaluate a Personal-Sized Seedless Watermelon Grown in High Tunnels.
Figure 1. Specialty watermelon trial pictures (Photo by Wenjing Guan).