“Onions need a sunny, sheltered site with fertile, well-drained soil. They won’t do well on acid soil [below pH 6.5].
“Onions are best suited to growing in the open ground, but you could grow a short row or two in large, deep containers or raised beds. They’re not suitable for growing bags.”
After planting your onions, you should make sure to cover them with fleece until they’re rooted, it added.
The fleece will protect them from hungry birds, which tend to be a problem for newly planted onion sets.