Growing Sweet Picnic Watermelon from Seeds in the UK 

Sweet Picnic Watermelon, also known as an “ice box” variety, is perfect for UK gardeners looking to grow juicy, sweet melons in a smaller space. This compact variety produces dark-skinned fruits with bright red flesh, weighing around 8-12 lbs and measuring up to 8 inches in diameter. Ideal for growing on trellises or in small gardens, these watermelons are early, drought-resistant, and quick to ripen, making them well-suited for the UK’s shorter summer season. Follow this detailed guide to successfully sow and grow Sweet Picnic Watermelon in your garden. 

When and Where to Sow Sweet Picnic Watermelon Seeds 

• Indoor Sowing: Start seeds indoors from early April to May to give your plants a head start. Watermelons require warm temperatures to germinate, so using a propagator or heated mat is essential for successful indoor sowing.
• Outdoor Sowing: Direct sowing is not recommended for watermelons in the UK due to the cooler climate. Instead, transplant young plants outdoors once the risk of frost has passed, usually from late May to early June. 

Ideal Growing Conditions for Sweet Picnic Watermelon 

• Soil Requirements: Watermelons thrive in well-drained, fertile soil. Prepare the planting area by digging and incorporating generous amounts of well-rotted compost or manure during the winter to improve soil structure and fertility. The ideal soil pH for watermelons is between 6.0 and 6.8. 
• Sunlight: Choose a warm, sunny, and sheltered location in your garden. Watermelons need at least 6-8 hours of direct sunlight daily to develop their sweet flavour and juicy texture. 
• Temperature: Maintain a temperature of 20-25°C (68-77°F) during germination. Watermelons are warm-season plants and prefer consistent warmth throughout their growth period. 

How to Sow Sweet Picnic Watermelon Seeds Indoors 

1. Sowing Depth and Containers: Fill 7 cm (3.5 inch) pots with a free-draining seed sowing mix. Sow one seed per pot, approximately 1 cm (½ inch) deep. Cover lightly with soil and water gently. 
2. Germination Conditions: Place the pots in a propagator or cover them with a clear plastic bag to maintain humidity. Keep the temperature between 20-25°C (68-77°F). Germination typically occurs within 5-10 days. 
3. Potting On: Once the seedlings have developed their first true leaves, transplant them into larger 13 cm (5 inch) pots. Grow them on in a warm, sunny spot for a few weeks before planting out. 

Transplanting Watermelon Seedlings Outdoors 

1. Hardening Off: Gradually acclimatise the seedlings to outdoor conditions by placing them outside during the day and bringing them in at night for about a week. This helps reduce transplant shock. 
2. Planting Out: After the last frost (usually late May to early June), plant the seedlings in their final positions. Space the plants approximately 60 cm (24 inches) apart. Choose a warm, sheltered spot with full sun or plant under glass or cloches for a more reliable crop. 
3. Soil Preparation: Ensure the planting area is well-prepared with plenty of organic matter. Watermelons are heavy feeders and will benefit from nutrient-rich soil. 

Caring for Sweet Picnic Watermelon Plants 

• Watering: Water regularly and deeply to encourage healthy root development. Keep the soil evenly moist, but avoid waterlogging. Reduce watering as the fruits near maturity to concentrate the sugars in the melons. 
• Feeding: Feed with a high-potassium liquid fertiliser every 14 days once the plants begin to flower. This will support fruit development and improve flavour. 
• Training and Pruning: Pinch out the growing tip at the 4-leaf stage to encourage side shoots (laterals). Train the side shoots along the ground or trellis. For vertical growth, support the fruit with slings or netting to prevent strain on the vines. 
• Pollination: Watermelons require pollination to set fruit. In cooler climates or under glass, you may need to hand-pollinate. Use a soft brush to transfer pollen from the male flowers to the female flowers, which have a small swelling at the base. 

Harvesting Sweet Picnic Watermelons 

• Harvest Time: Watermelons are usually ready for harvest around 75 days after sowing. To determine ripeness, tap the melon with your knuckles. A ripe watermelon will sound hollow. Additionally, the skin will have a slight dullness, and the tendril closest to the fruit will dry out and turn brown. 
• Harvesting Tips: Use a sharp knife to cut the melon from the vine, leaving a few inches of stem attached. Handle carefully to avoid bruising the delicate fruit. 

Common Questions About Growing Watermelons in the UK 

• Can I grow watermelons in containers? Yes, Sweet Picnic Watermelons can be grown in large containers or grow bags. Choose a container at least 12-15 inches deep and wide, and ensure it has good drainage. Support the vines with a trellis or allow them to trail over the edge. 

• How do I protect watermelons from pests? Watermelons can be affected by aphids and cucumber beetles. Use row covers to protect young plants, and remove any pests by hand or treat with organic insecticidal soap if necessary. 

• Why are my watermelons not setting fruit? Poor fruit set is often due to inadequate pollination. Hand-pollinate flowers if necessary, and ensure the plants have plenty of access to sunlight and are not overcrowded. 

By following these guidelines, you can enjoy a bountiful harvest of delicious Sweet Picnic Watermelons in your UK garden. Whether grown on trellises or in small spaces, these compact melons are perfect for fresh summer eating and are sure to impress with their sweet, juicy flavour. 

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