Choose a suitable location: Onions prefer full sun and well-drained soil. If you have heavy clay soil, consider planting in raised beds or containers.
Prepare the soil: Loosen the soil to a depth of about 6 to 8 inches and remove any weeds or debris. Onions prefer a neutral soil pH between 6.0 and 7.0. You can amend the soil with compost or other organic matter to improve fertility.
Plant the sets: Plant onion sets about 2 inches deep and 4 inches apart, with the pointed end facing up. If planting in rows, space the rows about 12 to 18 inches apart.
Watering: Onions require consistent moisture, especially during the growing season. Water the soil deeply and regularly, making sure not to overwater or allow the soil to dry out completely.
Fertilize: Onions are heavy feeders and will benefit from a balanced fertilizer every 4 to 6 weeks during the growing season. An all-purpose, granular fertilizer will work fine.
Mulch: Mulch around the onion plants to conserve moisture and suppress weed growth. Use a 2-inch layer of organic material, such as leaves or straw.
Thin out: As the onions grow, thin out the weaker plants so that the remaining ones have enough space to develop properly. Thin them to 4 to 6 inches apart.
Harvest: Onions are ready to harvest when the tops have fallen over and the bulb is fully formed. Carefully dig the bulbs and let them cure in the sun for several days to improve their storage life.
Store: Store the onions in a cool, dry place with good air circulation. They will keep for several months.