Planting red onion sets. Sets are the easiest way to grow onions - they’re little tiny onions that you plant straight into the ground. There are various ways you can space them; I have gone for rows about 9-10 inches apart to give enough space to hoe in between them, planted about 3 inches apart along the row. Plant them so that the pointed tops are just below the surface and cover with fine mesh as I have here to keep off pests if you’re in an area affected by allium leaf miner. This bed is shared with the shoots of the garlic I planted in November showing through in the back rows.