Before planting, divide the sets into two sizes. Use the largest sets for green table onions and the smaller sets for dry cooking onions.
Make sure the pH is about 6.5 to 8.5 and that the soil is well drained, firm and not freshly manured.
Planting the Onions
In early to mid May, you can start to plant your onion bulbs. To ensure you have straight rows you can pull a string across the gardening bed, and push the bulbs into the earth just along the string. Make sure you watch the freshly planted onions because birds like to peck them out of the soil. For that case keep a few extra bulbs and plant those when you notice that some bulbs have gone missing. If you find that the birds are too large a problem to fix with a few bulbs, it will be helpful to protect the onions with a bird netting. If you find that first pushes up the onion bulbs, push them back down to help them grow better. The frost will not harm the onion since it likes cool moist temperatures. Make sure you water the bulbs right after planting.
Green Table Onions
Choose the larger sets, the size of a nickel or larger, and plant in a row, with the roots down, ½ inch apart and 2 to 3 inches deep. Deep planting produces more white edible stems. In just 4 to 5 weeks the onions can be harvested. Continue to plant sets weekly for a continuous supply throughout the summer.
Dry Cooking Onions
Choose the smallest sets, the size of a nickel and smaller. Plant in a row, with the roots down 2 to 3 inches apart, and only deep enough to cover the top of the sets with dirt. Keep the rows of sets about 12 inches apart. When bulbs are ripe, the tops begin to yellow and fall over. When all the tops are dead, pull up plants and spread them in the sun for 3 to 4 days. Store in mesh bags.
During the Growing Season
Periodically hoe the ground around the onions shallowly and make sure the plants are kept free from weeds to give them as many nutrients as possible. Fertilize the plants every month with a general fertilizer to give the onion enough nutrients. At this point the bird netting can usually be removed since the green stalks will not be that attractive to the birds anymore.
Harvest and Storage
In late August and early September it will be time to start harvesting the onions. If you want smaller onions, you can harvest them earlier. When the bulb is ready for harvest the leaves will bend over, but usually you can just pull up the onions you deed for table use, or you can harvest all the onions at the same time. For the largest onion it might help if you lift them up with a fork. If you want to enjoy the onions in the winter months, you should spread the onions on sheets of newspaper in a dry, warm place for about 2 to 4 weeks. This place should be sunny, but don’t let the onions get rained on or have dew falling on them. This will make the sure the onions are dry and will not rot when you store them in the winter. Once the onions are dry you can store them like store bought onions in net bags, or in slatted trays, or you can tie the dried stems to string and you can hang them in a cool dry place. This method of storing will let you eat onions will into the spring.