Overview: Onions are a great crop for the small farmer. They're a kitchen staple and play a role in a great number of recipes. You can grow your basic yellow onion, or any of a number of fanciers and heirloom varieties, depending on your market.
Planting Time: Onion sets should be planted from mid-March to mid-April. Gently push onion sets into the soft soil so that just the tip shows. Firm up the soil around them.
If planting from seed, sow seeds ½ inch deep from late February through early April.
Spacing: Onion sets should be planted 4 inches apart from each other in rows 12 inches apart.
Onion seeds should be sown in rows 8 inches apart. Thin weaker seedlings, first to 2 inches apart and then to 4 inches apart.
Growing Notes: Onions do best in sunny, sheltered sites with well-drained, well-worked soil. Ground with fresh manure can cause onions to rot.
Onions also like being directly in the soil the best and don't thrive as well in containers or raised beds.
Pests and Problems: Birds are known to lift onion sets by pecking at the skins. To avoid this, remove loose skin at the top of the set before planting.
Onions can be prone to a few different diseases:
Onion white rot occurs when the leaves wilt and yellow, or the plant becomes loose in the soil. Throw away any infected bulbs and do not plant onions, leeks or garlic on this land again for eight years.
Onion downy mildew causes gray to green fuzzy patches on the leaves. Remove and destroy any infected leaves immediately to prevent spread.
Leek rust is a fungal disease that causes bright yellow spots on the leaves. Mild attacks are okay, but more severe infections can affect your crop yield. Remove affected plants. Keep conditions moist but not too wet and don't crowd plants too much. After leek rust, avoid the onion family in that spot for three years.
Maintenance: When the weather is dry, water onions. Feed occasionally. Mulch can help conserve soil moisture and help prevent weeds from taking over.
Once onion bulbs have swollen, stop watering and feeding and make sure the bulb is exposed to the sun.
Remove flower spikes as soon as possible.
Harvesting: Onion tops will flop over when they are ready, and they will begin to turn yellow. At this point, leave them in the ground for several weeks. Then use a garden fork to harvest onions carefully.
For storage, lay onions in the sun to cure for two to three weeks. If the weather is wet, cure onions in a shed or other enclosed area with good air circulation.