How to Grow Organic Onions

Red onions

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.