Onions are usually grown from small, immature bulbs known as sets. You can also grow them from seeds. This method is cheaper, but the plants take longer to establish and can have varied results.
Onions grow well on an open site on fertile, well-drained medium to light soil
Prepare the ground by working the soil and use a rake to smooth it out. Plant sets 10cm apart in rows 30cm apart. Gently push the set into the soil so just the tip is showing. Firm the soil in around them.
Onions grown from seed will need thinning out. First remove any weak seedlings and then spread the remaining ones initially to 5cm apart, then later to 10cm apart.
Water the onions in dry conditions and feed occasionally with a general-purpose fertiliser. You may mulch to conserve moisture if your soil is dry.
In June, feed lightly with a sulphate of potash fertiliser to help ripen the bulbs.
Stop all watering and feeding once the onions have swollen and remove any mulch or mounds of soil to expose the bulb to sunlight.
Remove any flower spikes as soon as you see them to prevent ‘bolting’ (running to seed).
Onions should be ready for harvesting from August to September, depending on when they were planted.
The foliage will turn yellow and flop over when the onion is mature. Once this happens, leave the bulbs for two weeks. Choose a dry day and gently lift with a fork.