It is the time of year to be thinking about getting ready to plant your onions. All onions need to be grown in full sun with well-drained, fertile soil and some added organic matter. They prefer a slightly acidic pH (6 to 6.5) and dislike competition from weeds, so either mulch or keep weed-free.

Onion bulb development is dependent on day length, with bulb development commencing as the days become longer , so this in late spring and they are usually harvested in early to mid-summer (December to January in the southern hemisphere).

Because of their day length sensitivity I do not successively plant onions and try and get all my onions planted by the shortest day (21st June in Southern Hemisphere).

I work out how many onions I use on average each week and multiply this by 52 and usually plant a few more. For me, that is around 300 plants. I then plant a mixture of white, brown and red varieties.
I apply liquid feed weekly, using a high nitrogen fertilizer to encourage leaf growth in the first few months. These leaves will then put lots of energy into producing a good sized bulb.

Step by Step Instructions:
In May

  • Select the onion varieties that you wish to grow.
  • Prepare garden beds by first cultivating and then testing the pH (adjust if necessary).
  • Add compost and well-rotted animal manure with a blood and bone mixed through it.
  • Mulch entire garden bed area.
  • To produce your own seedlings, plant selected seeds into pots filled with seed-raising mix, or sow seed directly into prepared garden beds. The other options is to simply buy punnets of seedlings once beds are prepared and plant these.
  • Once seedlings emerge, feed with half-strength power feed twice a week.

For a more comprehensive information on growing your own seedlings, check out mine here.

In mid-June

  • Transplant seedlings into prepared garden beds. You will need to plant then into rows 20cm apart with the seedlings about 10-15cm apart.
  • The most efficient way of planting seedlings is to move a narrow slice of mulch aside, create a furrow, then lay seedlings along the furrow with roots spread out at the bottom of the furrow and the leaves lying on one side.
  • Cover roots with soil.
  • Stand seedling up and press more soil up around them.
  • Replace mulch right up to the seedlings.
  • Water well.

After planting care

  • Fertilising
  • • Apply Seasol twice-weekly for 2 weeks
  • • Then apply Powerfeedweekly for 12 weeks
  • • Keep weed free

Harvest curing and storage

  • Once bulbs have formed and leaves start to yellow and fall over, stop all fertilising and watering. This is usually mid to late December in southern hemisphere.
  • When leaves have fully drooped, pull onions up.
  • They can be plaited at this stage or left lose (more about this later!)
  • Place in a hot, sunny situation to “cure” for a few days. If not plaited remove roots and withered tops and put them into onion bags. Onions store best if they are hung in a dark, dry spot as you use them.