Growing your own high quality organic onions is actually not very hard assuming you have well balanced soil and some patience. It has become one of our favourite crops to grow on the farm. Having your own supply of cured storage onions on hand for the year is very satisfying.
In our climate sow storage onions August or September at the latest. They can be direct seeded or sown to a plug tray(sow 5 or 6 seeds per plug) or broadcast to open flats. Raising seedlings has the benefit of avoiding the difficult early weeding pressure, and you can transplant straight into a weed free bed 6 weeks after sowing.
This is our farm preference: sow to plug trays then transplant in groups of 4 at 30cm apart. Transplanting in groups in this way allows much easier weeding over the long season and the onions develop just as well in bunches. Eliot Coleman may have pioneered this approach and it works.
Onions should be regularly weeded. Early leaf growth is the key to beaut onions at harvest time. They are ready to harvest late Jan/early Feb once the leaves start to yellow and fall down. Cure the onions in a well ventilated area. They can be stored outside in a cool shady and well ventilated area and they are good for the bulk of the year. Tying bunches with string and hanging for easy access works well.
Spring onions are good for sowing from Spring to early Autumn. We also prefer to sow these in plug trays, with 10-12 seeds per plug. Then transplant seedlings in bunches about 15-20cm apart. Pull bunches as required for fresh eating.