How to Sow Crunchy Spring Onion Seeds

Crunchy spring onions, also known as scallions or white Lisbon onions, are a versatile and easy-to-grow vegetable. Recognised for their crisp white bulbs and tender green stems, they have a milder flavour than traditional onions, making them a staple in UK kitchens. Ideal for growing in gardens, allotments, or containers, spring onions are a rewarding crop that can be harvested at various stages for different culinary uses. Whether sliced into salads, used in stir-fries, or added to soups, these onions are a must-have for home gardeners.

When and Where to Sow Crunchy Spring Onion Seeds

• Indoor Sowing: Start seeds indoors from late winter to early spring (February to April) for an early harvest. Ideal for growing in pots, containers, or window boxes placed in a warm, sunny spot.
• Outdoor Sowing: Sow directly outdoors from late spring (April to June) once the risk of frost has passed and the soil is workable. A late summer sowing (August) will provide an autumn crop.

Ideal Growing Conditions for Crunchy Spring Onions

• Soil Requirements: Prefers light, well-drained, fertile soil enriched with compost or well-rotted manure. Avoid heavy clay soil, which can restrict root development. The ideal soil pH is 6.0-7.0 for optimal growth.
• Sunlight: Thrives in full sun, but will tolerate partial shade. Ensure the plants receive at least 6 hours of sunlight per day for the best growth.
• Temperature: Ideal germination temperature: 15-20°C (59-68°F). Spring onions are hardy and can tolerate cooler temperatures, but young plants need protection from frost.

How to Sow Crunchy Spring Onion Seeds Indoors

1. Prepare Containers: Fill pots or seed trays with fine, well-draining seed compost. Ensure containers have drainage holes to prevent waterlogging.
2. Sowing Depth: Sow seeds 1.25 cm (½ inch) deep, spacing them evenly. Cover lightly with compost.
3. Watering: Mist the soil lightly to keep it evenly moist but not soggy.
4. Germination Conditions: Place containers in a bright, warm spot (15-20°C). Germination takes 10-14 days.
5. Thinning Seedlings: If overcrowded, thin seedlings to 5 cm (2 inches) apart to allow space for growth.

How to Sow Crunchy Spring Onion Seeds Outdoors

1. Soil Preparation: Loosen the soil and mix in organic compost or well-rotted manure. Remove weeds and break up clumps.
2. Sowing Depth: Sow seeds 1.25 cm (½ inch) deep in rows. If sowing in clusters, space seeds 5 cm (2 inches) apart.
3. Spacing: If growing in rows, allow 30-45 cm (12-18 inches) between rows for easy maintenance.
4. Watering: Water lightly to keep the soil moist but avoid overwatering.
5. Thinning Seedlings: Thin plants as needed to 5 cm (2 inches) apart for proper development.

Caring for Crunchy Spring Onion Plants

• Watering: Keep soil evenly moist, especially during dry spells. Avoid overwatering, as soggy soil can lead to root rot.
• Fertilising: Apply a general-purpose fertiliser once during the growing season for healthy growth. If soil is already fertile, additional feeding may not be necessary.
• Weeding and Mulching: Keep the area weed-free to prevent competition for nutrients. Apply a thin layer of mulch to retain moisture and suppress weeds.
• Preventing Bolting: Bolting occurs when plants prematurely produce flowers. Prevent this by keeping soil consistently moist and harvesting regularly.

Harvesting Crunchy Spring Onions

• When to Harvest: Harvest at 60-120 days after sowing, depending on size preference. For mild onions harvest early; for stronger flavour, wait longer.
• How to Harvest: Gently pull up onions by the base to keep bulbs intact. For continuous harvests, sow seeds every few weeks throughout the growing season.
• Transplanting Seedlings: If transplanting from indoors to outdoors, wait until seedlings are 10 weeks old. Clip plants to 7 cm (3 inches) tall before transplanting to 5 cm (2 inches) deep in their final location.

Common Questions About Growing Spring Onions in the UK

• Can I grow spring onions indoors year-round? Yes! Spring onions grow well on a sunny windowsill or in a conservatory throughout the year.
• How do I prevent spring onions from bolting? Keep the soil moist and avoid sudden temperature fluctuations. Harvesting regularly also helps prevent bolting.
• What is the best way to store harvested spring onions? Store in the fridge, wrapped in a damp paper towel or placed in a glass of water to keep fresh for up to a week.

By following these steps, you can enjoy a continuous supply of fresh, crunchy spring onions straight from your garden, allotment, or even a windowsill. With their mild, crisp flavour and easy-growing nature, they’re a perfect addition to any UK gardener’s vegetable collection. 

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