In My Seed Box For 2026 - Onion Sets

In the UK, onion sets are small, immature onion bulbs, grown from seed the previous year and harvested early to be planted out in autumn or spring for a quicker and more reliable crop than starting from seed. They offer a convenient way to grow onions, especially for novice gardeners, and provide an earlier harvest, though there is a smaller variety selection compared to seeds and they are typically more expensive.  

How they are made and why they are used

• Crowded growth: Onion seeds are sown densely, leading to small, undeveloped bulbs.
• Harvested early: These tiny bulbs are harvested before they reach full size. 
• Ready to plant: Unlike seeds, they are already at a more advanced stage of growth, making them quicker and more reliable to sprout. 

Advantages of using onion sets

• Ease of growth: 

  Onion sets are an easy and fast way to get a harvest of onions, ideal for beginners. 
• Earlier harvest: 

  Planting sets can lead to an earlier harvest compared to growing from seed. 
• Heat treatment: 

  Many sets are heat-treated to prevent them from bolting (producing a flower instead of a bulb), which is a common issue when growing from sets. 

Things to consider

• Cost: Onion sets are generally more expensive than onion seeds.
• Variety: The range of onion set varieties is much smaller compared to the vast selection available as seeds. 
• Bolting risk: Sets are more prone to bolting than seeds, though heat-treated varieties significantly reduce this risk. 

At the moment I have not selected any sets, but my daughter prefers Red onions and l normally grow a selection of colours. 

Varieties of onion sets I have grown in the past include:-

 

Karmen from Mr Fothergill's. 

Pink Panther from Mr Fothergills 

Snowball from Mr Fothergills 

In My Seed Box For 2026 - Index