🧅🌱 Growing Onions from Sets: A Step-by-Step Guide
🌿 Introduction: Why Grow Onions from Sets?
Growing onions from sets is one of the easiest and most reliable ways to produce a good onion crop, especially in the UK climate. Onion sets are small, immature bulbs that establish quickly and are less prone to failure than seed-grown onions.
Keter Manor Outdoor Apex Double Door Garden Storage Shed (6 x 8ft)
A durable and stylish beige and brown garden storage shed perfect for storing garden tools, equipment, bikes, and outdoor essentials. Weather-resistant, low maintenance, and ideal for any garden or allotment setup.
🌱 Compost & Soil Improvers
Give your garden beds a boost before winter with compost and organic matter.
Shop Compost & Soil Improvers
🌿 Autumn Plant Feed & Fertiliser
Prepare your soil for autumn planting with suitable fertilisers and soil nutrients.
Browse Garden Fertilisers
🥬 Seed Trays & Propagation Kits
Keep growing through autumn by starting suitable hardy crops under cover.
Shop Seed Trays
Gardeners choose onion sets because they:
✔ are beginner-friendly
✔ grow faster than seed
✔ cope well with cooler conditions
✔ produce consistent results
This guide explains how to grow onions from sets, from choosing the right varieties to harvesting and storing your crop.
Below
⭐ Check Out Our Recommended Products
• Onion Sets
Choose firm, healthy sets with no mould or softness.
Click here to see them
• Multi-Purpose Compost or Garden Soil Improver
Improves soil structure and drainage.
Click here to see them
• Hand Trowel
Ideal for planting onion sets accurately.
Click here to see them
🧅🧠 1. What Are Onion Sets?
Onion sets are:
✔ small, partially grown onion bulbs
✔ produced the previous season
✔ planted to mature into full-sized onions
They reduce the risk of bolting compared to seed-grown onions.
🌱📅 2. When to Plant Onion Sets in the UK
✔ spring sets: March to April
✔ autumn sets: September to October
Plant when the soil is workable and not waterlogged.
🌿🌞 3. Best Growing Conditions for Onions
Onions grow best in:
✔ full sun
✔ free-draining soil
✔ open, airy sites
Avoid heavy, compacted soil where bulbs may rot.
🌱✋ 4. How to Plant Onion Sets
✔ plant sets point-up
✔ just push the tip above soil level
✔ space sets 10–15 cm apart
✔ rows spaced around 25–30 cm apart
Firm the soil gently and water well.
💧🌿 5. Watering and Feeding Onions
✔ water during dry spells
✔ avoid overwatering
✔ feed lightly with a balanced fertiliser
Stop feeding once bulbs begin to swell.
🌱🪴 6. Weed Control and Maintenance
✔ keep beds weed-free
✔ shallow hoeing to avoid damage
✔ mulch lightly if needed
Onions dislike competition from weeds.
🧄🐦 7. Protecting Onion Sets from Pests
✔ birds may pull up sets
✔ cover with netting if needed
✔ remove flower stalks if they appear
Early protection improves success rates.
🌾✂️ 8. When and How to Harvest Onions
✔ harvest when leaves turn yellow and fall
✔ gently lift bulbs from soil
✔ allow to dry (cure) in a warm, airy place
Proper curing improves storage life.
🏡📦 9. Storing Home-Grown Onions
✔ store in cool, dry conditions
✔ use mesh bags or strings
✔ check regularly for rot
Well-stored onions last for months.
⚠️❌ 10. Common Problems When Growing Onions from Sets
❌ bolting (flowering early)
❌ waterlogged soil
❌ overcrowding
❌ poor storage conditions
Good spacing and timing prevent most issues.
🌟 FAQs
Are onion sets better than seeds?
They’re easier and quicker, especially for beginners.
Can onion sets be grown in containers?
Yes — use deep pots with good drainage.
Why are my onion sets going to seed?
Usually due to stress or cold conditions.
Should onion sets be covered completely?
No — the tip should remain just above soil level.
How long do onions take to grow from sets?
Around 20–24 weeks.