Seedless Triploid Watermelon Production
2Pages

Seedless Triploid Watermelon Production 955 Benton Ave., Winslow, ME 04901  Phone: 1-877-564-6697  Fax: 1-800-738-6314 Email: service@johnnyseeds.com  Web Site: Johnnyseeds.com TRIPLOID WATERMELON (Citrullus lanatus var. lanatus) Hybrid triploid watermelons, commonly called seedless watermelons, are more difficult to grow than diploid varieties. However, they can be grown successfully with some extra care and management. The seedless trait is a result of a traditional cross of a normal seeded diploid parent with a tetraploid parent. Although fruits from these plants are considered seedless, pips — thin, edible, whitish ovules — along with an occasional typical black seed may develop if the plants are exposed to stress. SITE SELECTION: Watermelon prefers a light, well-drained soil with a pH of 7.0. A location with a southern exposure is ideal, as it will help provide additional warmth. Soil moisture is important in the early stages of growth and during pollination, when the fruits are setting. Drip irrigation can prevent excess water on the foliage, which can lead to disease. Do not provide irrigation in the last week before fruits are ripe, as overwatering can cause bland fruit. To maintain warm temperatures, the use of plastic mulch and row covers is recommended. In cool areas, solar mulch is preferred over black mulch because it warms the soil better. Plastic mulch also suppresses weeds around drip irrigation. SEED STARTING: Triploid seeds germinate weakly. Failure can occur if the soilless mix is too cool or too wet. The mix should be coarse, well drained, warm, 85°F/29°C, and moist but not wet. If you can squeeze a handful and get free water, the mix is too wet and if it is below 85°F/29°C it is too cool. Use a growth chamber or heat mat to keep the temperature of the mix at 85°F/29°C. This warm temperature is critical for proper germination and early seedling vigor. Delay sowing the seedless watermelons and pollenizer until 3 weeks before the outdoor soil temperature is expected to be warm, at least 65°C/18°C, and after the danger of frost has passed. The triploid seeds and the pollenizer diploid seeds that are sent with the order should be sown at the same time, in separate trays. Fill 2–2½ inch cell-type containers with the soilless mix. Sow 1–2 seeds per cell, covering ½ inch deep with the pointed end of the seed up or at a 45-degree angle to facilitate the shedding of the seed coat during emergence. Cover the plug trays with thin poly sheeting to prevent drying. Keep the poly-covered trays out of direct sunlight to avoid overheating. If the mix becomes too dry before seedlings emerge, mist with warm water, but keep on the dry side. SEEDLING DEVELOPMENT: When seedlings emerge, usually in 2–3 days, move them to full sun in the greenhouse. Maintain the greenhouse temperature at 85°F/29°C until full emergence; 70°F/21°C is the minimum, even at night. Thin to 1 plant per cell by using scissors to clip unwanted plants at their base, rather than by pulling them out. Once all the seedlings have emerged, reduce greenhouse air temperature to 75°F/24°C during the day and 65°F/18°C at night. Irrigate seedlings with water that has been preheated to 70–75°F/21–24°C. ROW COVERS: As mentioned before, the use of row covers can help maintain the warm temperatures necessary for a successful crop. Row covers make for earlier crops and better yields, especially in the North. Remove the covers when plants have female flowers — the flowers with a tiny fruit at the base of the blossom. Copyright © 2016 Johnny’s Selected Seeds. All rights reserved.

TRANSPLANTING: Seedlings are ready for transplanting to the field about 3 weeks after sowing. The seedlings should have 2–3 true leaves, and roots that have sufficiently filled the cell to hold the soil mix when the plant is removed. Younger plants may be too fragile for handling and planting, older plants, particularly ones with 4 or more true leaves, are susceptible to transplant shock, which can delay plant growth and reduce fruit size and total yield. Remove plants from cells carefully to avoid tearing roots. Transplant to the field only after the danger of frost has passed and...