SCIENTIFIC NAME: Citrullus lanatus var. lanatus
CULTURE: A light, well-drained soil with a pH of 6.5–7.5 and a northern exposure is ideal. Good soil moisture is important in early stages of growth and during pollination when fruits are setting. After this point do not water the last week before fruits are ripe, as overwatering can cause bland fruit. Citrullus lanatus is native to the dry areas of tropical and sub-tropical Africa, therefore very demanding in terms of sunlight and temperature throughout the growing period.
The main reasons for poor germination in triploid watermelon seeds is excess of water in the sowing media and low temperatures. Triploid watermelon seeds has a thicker coat and has larger air space compared with diploid watermelon. If water is excessive uptake of oxygen into the embryo may be restricted resulting in decreased germination.
TRANSPLANTING: Sow indoors in 50-cell plug trays or 50-75mm peat pots in late October or one month (no sooner!) before transplanting outdoors. Plant 2 seeds per cell or pot, about 12-25mm deep. Keep temperature 27–32°C until germination. Handle young plants carefully and never let the soil dry out. Grow seedlings at 24°C, During nursery development exposed seedlings to temperature above 25C. Reduce water and temperature for a week to harden seedlings. When the weather is frost-free, warm, and settled, transplant 60-90cm apart in rows 2-3m apart, or thin to 1 plant/pot or cell with scissors and transplant 45cm apart. Even hardened watermelon seedlings are tender! Do not disturb roots when transplanting, and water thoroughly.
DIRECT SEEDING: Sow 1–2 weeks after last frost when soil is warm, above 21°C, 3 seeds every 45-90cm, 12-25mm deep, thinning to 1 plant/spot.
TRIPLOID/SEEDLESS: Start indoors under favourable conditions to ensure proper germination. A polleniser watermelon, or normal seeded watermelon, is required for fruit set. A ratio of three triploids (seedless) plants to one diploid (seeded) plant is recommended. Choose a pollenizer with fruits that can be distinguished from the seedless fruits. It is important to choose a polleniser cultivar that produces male flowers within the same time frame that the female flowers appear on the seedless plant.
FERTILISATION: A standard fertilisation program per metre is 12-18g N, 15-20g P2O5 and 15-22g K2. For grafted watermelon, the fertilisation of P2O5 & K2 is significantly less and must be adjusted according to local conditions. Watermelons grow best when soil pH is between 6-7. Prior to pollination and fruit set don’t overwater or fertilize.
POLLINATION & FRUIT DEVELOPMENT: For pollination bees are essential. One hive per acre is recommended. Any spraying should be done only with bee-friendly applications. Optimal temperature for pollination and fruit setting is 20-25c, up to 35c is acceptable. Good exposure to sunlight will enhace fruit qualities. Full maturity is at 35-45 days after setting in optimal conditions (nights 15-20c at night and days 25-35c).
ROW COVERS: Since watermelons like consistently warm conditions, plastic mulch and row covers will make for earlier crops and better yields, especially in southern Australian and highland areas. Remove covers when plants have female flowers (tiny fruit at base of blossom).
DISEASES: Choose varieties resistant to diseases in your area. “Sudden wilt” is a complex disease and cold weather stress syndrome in late summer when plants have a heavy set of ripening watermelons, can cause plants to wilt almost overnight. Keep plants healthy with good fertility and irrigation to avoid sudden wilt.
INSECT PESTS: Protect against insects such as beetles with floating row covers applied at transplanting, or control with insecticides such as pyrethrin.
RIPENESS: There are 3 ways to tell when a watermelon is ripe: 1) the tendril nearest the point on the vine where fruit stem attaches is browning/dead; 2) the spot where the fruit rests on the ground is yellow; and 3) the classic mystery — you hear “punk,” as opposed to “pink” or “pank,” when you flick the melon with your fingers.
STORAGE: Hold at 7°C and 85% relative humidity 2–3 weeks.
AVG. DIRECT SEEDING RATE: 30g/100m, 1,000 seeds/150m, 650g/acre at 3 seeds every 45cm, in rows 2m apart.
TRANSPLANTS: Avg. 540 plants/30g
SEED SPECS: Seeds/500g: Avg. 7,900
Quick Facts
- Latin Name: Citrullus lanatus var. lanatus
- Life Cycle: Annual
- Hybrid Status: F1
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