Some guidelines for planting onion sets:
1. Plant in well dug soil in an open site.
2. Do not plant in recently manured soil as overly fertile ground will result in lush green growth but poor root development, and it's the root we are interested in. Perhaps use a patch of ground that you formerly grew vegetables that had received plenty of compost/organic matter in the Spring.
3. Place your sets on your well dug soil so you can plan your spacing. Here is my plot; I have planted closer than often recommended after seeing how well onions can grow close together.
3. Once you have arranged your sets, loosen the soil around the bulb so you can push it gently just below ground level, not deep in the way you would plant garlic or flower bulbs. Some recommend leaving the tip of the onion exposed but you may have problems with birds uprooting them. Smooth over the soil surface.
4. Bulbs should only require watering in particularly dry weather.
5. A long growing season is necessary for the development of good sized bulbs.
6. To harvest onions for fresh use, you can lift them as you need them once they have reached a decent size. For storage, wait until the stalk has naturally began to fall over. Lift and lay in a warm dry place to dry until the outer skins are paper dry. Harvested onions can be stored for months hanging in nylon tights (knot each one individually to separate).