Seedless Watermelon (Triploid)
Triploid watermelons are sterile and do not produce viable seed. They require a pollinator variety planted in alternating rows (e.g., 1 pollinator for every 2 rows of triploid). Direct seeding is not recommended due to poor emergence in temperatures below 80ºF and thick seed coats that may stick to cotyledons, causing damage.
Temperature
Germinate seeds at 90ºF. In cooler areas, warm transplant flats in the sun or use dark rooms with 90ºF and 95% humidity. Emergence takes 4–5 days. Transplants are grown for 3 weeks before setting in the field.
Soil
Plant in well-drained sandy loam, preferably not used for cucurbits in the past 5 years. Use raised beds to improve early-season warmth and drainage. Avoid compaction and monitor moisture during seedling establishment.
Planting
Use transplanting only. Sow 1" deep in greenhouse. Set transplants deeper in the field than in the tray. Fully bury peat pots to avoid moisture wicking. Water transplants thoroughly to settle soil. Include pollinator rows across the field for fertilization. Melons from pollinator rows should be distinct and market-acceptable.
Spacing
24–48" in row and 72" between rows
Pollination
Triploid watermelons produce little or no pollen and rely on seeded pollinators. One strong bee hive (30,000–50,000 bees) per 1–2 acres is recommended. Plant pattern: outer beds as pollinators, then two rows of triploid, one row of pollinator, and repeat. Ensure pollinators are distinguishable at harvest.
Harvest
Harvest when the tendrils are brown, the ground spot turns yellow, and thumping yields a hollow sound. High-quality fruit has a sugar content of 10% or more. Use a refractometer to verify. Harvest with a knife or clippers and place bottom-down to prevent sunscald. Consume within 2–3 weeks of harvest.
Cost Considerations
Triploid production is more expensive due to seed cost, transplanting, and the need for pollinators. Growers should secure higher prices to offset these inputs. Uniform stand establishment is critical; overseeding and thinning are not cost-effective options.
For more information, please see links below:
- Penn State - Watermelon Production
- University of Georgia - Watermelon Guide
- University of Kentucky - Watermelon
Note: This information is summarized. Additional details and expanded guidelines can be found in our production sheets available in the Holmes Seed Grower's Guidebook.
Downloadable Copy: