Last Updated on: December 22, 2025

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🧅🌱 How to Plant and Grow Spring Onions Successfully: A Complete UK Guide

🧅 Introduction: Why Grow Spring Onions?

Spring onions (also called salad onions) are one of the easiest and quickest crops to grow in the UK. They take up very little space, grow well in the ground or containers, and can be harvested in as little as 6–8 weeks. Perfect for beginners, they provide a steady supply of fresh, mild-flavoured onions for salads, stir-fries, and garnishes.

This complete UK guide explains when to plant spring onions, how to grow them successfully, and how to avoid common problems.

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📅 When to Plant Spring Onions in the UK

Spring onions can be grown almost year-round in the UK with the right approach.

🌱 Outdoor Sowing

• March to September
• Soil temperature should be above 8°C

🏡 Indoor / Protected Sowing

• February onwards (windowsill, greenhouse, or polytunnel)
• Enables earlier harvests

❄️ Overwintering Crops

• Sow August to September
• Harvest the following spring

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🌍 Choosing the Right Growing Position

Spring onions prefer:

• Full sun or light shade
• Free-draining soil
• Shelter from strong winds

They grow well in:

• Raised beds
• Containers
• Window boxes
• Allotments and small gardens

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🌱 How to Sow Spring Onion Seeds (Step-by-Step)

1️⃣ Prepare the Soil

• Remove weeds
• Rake soil to a fine tilth
• Add compost if soil is poor

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2️⃣ Sow the Seeds

• Sow seeds 1 cm deep
• Space rows 15–20 cm apart
• Scatter seeds thinly along the row

Spring onions do not need much space.

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3️⃣ Water Gently

• Water after sowing
• Keep soil moist but not waterlogged

Seeds usually germinate in 7–14 days.

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🪴 Growing Spring Onions in Containers

Spring onions are ideal for pots.

Container Tips:

• Use pots at least 15 cm deep
• Fill with free-draining compost
• Sow seeds evenly across the surface
• Thin lightly if crowded

Containers dry out faster, so water regularly.

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💧 Watering & Feeding

Watering

• Keep soil consistently moist
• Avoid letting soil dry out completely
• Reduce watering in cool weather

Feeding

• Usually not required
• A light liquid feed helps in poor soil

Too much feed encourages leaf growth but weak flavour.

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🌿 Ongoing Care

• Keep weed-free
• Thin seedlings if overcrowded
• Protect young plants from birds
• Mulch lightly to retain moisture

Spring onions need very little maintenance.

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🧅 When & How to Harvest Spring Onions

• Ready to harvest in 6–8 weeks
• Pull gently from the soil
• Harvest when stems are pencil-thick or larger

For continuous harvests:

• Sow small batches every 2–3 weeks

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⚠️ Common Problems & How to Avoid Them

Thin or weak growth

• Soil too dry or overcrowded

Plants bolting (flowering early)

• Heat stress or inconsistent watering

Pests (onion fly)

• Use fleece
• Practice crop rotation

Spring onions are generally trouble-free.

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❓ Frequently Asked Questions

Can I grow spring onions all year round?
Yes, with protection in winter.

Do spring onions regrow after harvesting?
No, but you can sow regularly for constant supply.

Can I grow them indoors?
Yes — they grow well on bright windowsills.

Are spring onions suitable for beginners?
Absolutely — they’re one of the easiest crops to grow.

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🧠 Key Takeaway

Spring onions are a fast, reliable, and rewarding crop for UK gardeners. By sowing regularly, keeping soil moist, and choosing sunny positions, you can enjoy fresh spring onions almost year-round with minimal effort — whether growing in the garden, allotment, or containers.

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