Germination temperature
Minimum 16 °C (60 °F); best 21-35 °C (70-95 °F).
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Watermelon is a heat-loving vine that needs warm soil, full sun and a long frost-free season. Sow it directly into warm ground or transplant very young seedlings, keep moisture even and let bees do the pollinating.
Minimum 16 °C (60 °F); best 21-35 °C (70-95 °F).
About 2.5 cm (1 in).
About 12 days at 20 °C (68 °F), 5 days at 25 °C (77 °F), 3-4 days at 30-35 °C (86-95 °F).
Seed is covered; grow in full sun.
None needed.
Direct sow in warm soil, or transplant very young seedlings from plantable pots.
Use plump, clean seed. In India TNAU treats seed before sowing with Trichoderma viride (4 g per kg of seed) or Pseudomonas fluorescens (10 g per kg) against seed- and soil-borne disease.
Not needed. Watermelon seed takes up water readily once the soil is warm.
Not needed. This is a warm-season crop with no cold requirement; cold soil is the main cause of failure.
Not needed. Warm, moist soil matters far more than pre-soaking.
Seed germinates poorly below 16 °C (60 °F) and hardly at all at 5 °C (41 °F). The best range is 21-35 °C (70-95 °F); above 40 °C (105 °F) germination fails. In gardens wait until the soil has reached 18-21 °C (65-70 °F).
About 2.5 cm (1 in). Sow 4-5 seeds per hill, or 1-2 seeds per pot for transplants.
Well-drained sandy loam rich in organic matter, pH 6.0-7.5. TNAU uses long channels or, with drip irrigation, raised beds 1.2 m wide and 30 cm high.
Water before sowing and keep the soil moist but not waterlogged. Seed sown into cold, wet soil often damps off.
No light is needed for germination. Move pot-grown seedlings into full sun as soon as they emerge so they stay short and sturdy.
At warm soil temperatures seedlings appear in 3-5 days; at 20 °C (68 °F) it takes about 12 days.
Watermelon roots dislike disturbance. Sow 3-4 weeks before planting out in peat or other plantable pots and set the whole pot in the ground when plants have 1-2 true leaves; TNAU transplants nursery seedlings at about 12 days. Harden plants off for a few days first, starting in shade.
Thin each hill to 2 strong plants (TNAU thins 15 days after sowing). Space hills about 0.9 m (3 ft) apart along channels 2.5 m (8 ft) apart, or 60-90 cm (2-3 ft) apart in rows 1.8-2.4 m (6-8 ft) apart.
Keep the bed weed-free until the vines cover the ground. A mulch of straw or plastic film saves water and suppresses weeds; with plastic mulch run drip lines underneath.
Cause: sowing into cold, wet soil (damping-off). Fix: wait for soil of at least 18 °C (65 °F), sow on raised beds and use treated seed.
Cause: poor pollination. Watermelon has separate male and female flowers, each female flower is open for only one day and bees must carry the pollen. Cool, rainy or windy weather and insecticide sprays reduce bee visits. Fix: avoid spraying during flowering and keep soil moist at bloom.
Cause: heavy irrigation after a long dry spell. Fix: water regularly and evenly.
Cause: gummy stem blight, downy and powdery mildew and anthracnose in wet weather; Fusarium wilt and root-knot nematodes in the soil. Fix: water at soil level instead of overhead, rotate the bed and choose resistant varieties where available.
Cause: fruit fly. Fix: pick up and destroy affected fruit, plough to expose pupae and use traps; TNAU also lists neem oil (3%) as a spray.
In temperate climates sow after frost once the soil is warm. In Tamil Nadu TNAU sows in November-December; January-February sowings give a summer crop.
Small, quick varieties such as Sugar Baby suit home gardens. TNAU also lists Arka Manik and the hybrids Arka Jyoti, Pusa Bedana and Suvarnima.
Work well-rotted manure plus phosphorus and potassium into the bed before sowing, and give nitrogen about 30 days after sowing (TNAU schedule).
Most varieties ripen 70-90 days after sowing in gardens; field crops in Tamil Nadu take about 120 days. Look for a creamy-yellow ground spot, a dull rind and a dry tendril next to the fruit stem. Thumping is unreliable on its own.
Sow watermelon into warm, sunny ground for sweet summer fruit.
Usually the soil was too cold or too wet. Watermelon needs at least 16 °C (60 °F) and comes up in 3-5 days in warm soil; in cold, wet soil the seed rots.
Yes, but only very young plants. Sow in plantable pots 3-4 weeks before planting out and transplant at 1-2 true leaves without breaking the root ball.
In South India TNAU recommends November-December sowing; January-February sowing gives a summer harvest. Avoid sowing into cold or waterlogged soil.