Onion plants have a sparse rooting system and feed within a limited area. You should prepare your garden soil for your onions by applying a commercial fertilizer at the rate of one pound for every 25 feet. The fertilizer should be worked into the soil prior to planting your onions.
- For an early onion crop, you should start your onion seedlings indoors. Plant your seeds in flats about two months prior to the planting date. You should sow about five seeds per every square inch.
- When the seedlings are ready for the garden, you should cut back the tops to about four inches. A good guide for knowing when your seedlings are ready to transplant into your garden is to compare them to a pencil. When they are pencil size, they are ready - weather permitting. Onions that are grown from seedlings indoors should be planted in the garden mid-spring.
- If you would like, you can wait and sow your onion seeds directly into the ground in the spring when all threats of frost have passed. To plant directly into the garden, you should make furrows which are about a foot apart. Place four to five seeds per every inch in the furrows.
- You should set your onion seedlings out in the garden with spacing of four to six inches between each plant. Your onion rows should have about a foot between them. (You should use this same spacing guide when you are thinning out onion seedlings that you have directly sown into the garden.)
- When harvesting your onions, you should loosen the bulbs with a fork and allow them to dry out in the garden for a few days. This will allow the skins to toughen and the quality of your onion will be better.
You should not try to clean the onion (or remove the soil around the onion) until the onion is entirely cured.
- If you want to have a good supply of onions, it should be noted that you can do both types of planting methods.
Start one set of onion seeds indoors about two months before the expected planting date. Then, sow another set of onion seeds into your garden in the middle of spring when the weather permits. (You should plant your seedlings that are grown indoors at the same time that you sow your onion seeds directly into the garden.)
Onion sets will generally mature within 90 days. Onion seeds will be mature in 180 days.