How to Grow Onion Sets


  • Sowing Instructions
  • Crop Maintenance
  • How to Harvest
  • Storage
  • Pests & Diseases

Sowing Instructions

  • Sowing time: From mid March, assuming frost has passed
  • Sowing Location: Sow direct into rows
  • Sow 1 set every 10cm
  • Alternatively sow them every 5cm & thin later
  • The closer you sow your onion sets the smaller your harvested onions will be
  • Prepare soil prior to sowing, dig & manure your soil the previous autumn if possible
  • A sunny site with good drainage is ideal
  • To sow simply push the set into the soil
  • Sowing depth: onion set's tip should be just below soil surface
  • Space rows 15cm apart

Crop Maintenance

  • Keep moist
  • Weed regularly during summer months
  • Check sets early to see if birds have lifted them from the soil
  • If so, simply re sow them
  • Apply a general fertilizer if needed and rake the surface on a dry day
  • If your soil is a heavy clay it is recommended that you improve you soils drainage
  • Alternatively place a small amount of horticultural grit beneath seeds prior to sowing


  • Harvest when the bulbs have swollen and when the stems turns yellow and falls over
  • Using a garden fork, slightly lift the onions in their position. lift to snap the onion's roots preventing further growth
  • Leave for 14 days and carefully remove on a dry day
  • You can speed up the process by bending and tieing the stems once they start to yellow
  • On a dry day lift your onions and place them out in the sun
  • Depending on the size of your onions and weather conditions it can take up to 4 weeks for the onions to dry


  • Consume any damaged bulbs first
  • Short term storage in the fridge
  • Can be stored for up to 7 months in a cool dry place
  • You can also tie up your bulbs using their own stems or some cord

Pests & Diseases

  • Bird attack is most likely the biggest threat to onions
  • Netting should be used to protect against birds that pull up roots
  • Other pests and diseases include: Onion fly, root fly, bolting and downy mildew


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