How to Prune onion?
No pruning required

onion · Allium cepa
Also known as: tree onion; shallot
Grow in fertile, moisture retentive, but well-drained soil in full sun. Thin-out young plants growing from seeds in spring. Yellowing and toppling of the foliage is a sign that the shallots are reaching maturity. Lift and store in a cool dry place. See how to grow: onions for further advice
No pruning required