Onions are a great bulb vegetables which do well in the British climate and can be grown at home from sets or seeds to give you a great year round addition to your meals.


  • Onions love well drained and sunny locations in your garden or allotment.  If your soil is heavy it is definitely worth improving the soil before planting (use grit and bulky matter).  If you are planting in heavy soil it is also worth planting in ridges of soil (around 10cm in height) to help reduce the soil moisture.



  • January to Feb when the temperature is around 10-15°C
  • Put 5-6 seeds per module of damp compost.  The onions will spread themselves as they grow
  • If you are after a year round crop you can sow again in spring for a August harvest, then again in late summer or autumn for a crop in June the following year


  • A simple way of growing onions, sets are an immature bulb.
  • Prep the ground a couple of months before planting using and digging over manure
  • Pop the sets in during spring into shallow drills and cover so their neck is just visible.

Care while growing

  • Regularly week – onions do to suppress weeds and can easily become swamped
  • Water sparingly

Problems, pests and diseases

  • One of the common issues with onions is bolting (going to flower/seed) which can occur if there is a late cold spell or there has been hot and dry conditions.  Heat treated sets or varieties which mature late can help reduce the likelihood of this happening.
  • Onion neck rot is a fluffy grey fungal growth around the neck of the onion.  Buying from a good supplier and not growing in the same site more than 2 years in a row can also help reduce the chance of this happening.
  • Onion white rot is a dense fluffy fungal growth around the root and base of the bulb.  Once found, remove the infected plant quickly and don’t grow in onions in that location for at least eight years.
  • Onion fly larvae eat the route of the bulb and may burrow into them.  Growing onions from sets helps to reduce this as well as going alongside carrots.  If you find a bulb with an infestation, remove it before the larvae move to the soil to pupate.
  • Onion thrips is an insect which attack both onions and leaks.  A fine white mottling to the foliage which indicate an attack on the onion and can occur during dry, hot weather.  The damage caused by the insect can result in a smaller crop.


  • Harvest when the foliage starts to go yellow and die back.  It is not good practice to bend the leaves to speed this up.
  • Lift the bulb and place in a warm dry place for a couple of weeks to allow the onions to dry out.


  • Onions can be stored, once the foliage is fully dry, for around 3-6 months in a cool dry place either by hanging in nets or plaits, or packed in layers of boxes.