I have had very good luck growing onions – and am I glad! My favorite are red onions – they are so much better than yellow or white onions on most everything. Unfortunately they do not last as long as yellow ones which is not a problem because they get used so quickly. Another plus is I can grow green onions; which I love. Check out some good recipes at dougthecook.com. Make sure the onions bought are long-day onions; short-day onions are for the South and do not grow well in the Midwest.
My onions are planted in the spring from sets as that is the easiest way. If the onion is larger than a dime, use those for green onions. Remember to plant them with the roots down (one year I planted several with the roots up – they were about one half the size of the ones planted with roots down). Good Friday is when I plant the cool weather crops: onions, potatoes, spinach, lettuce, and radishes. You could plant the last week of March but Cletus insists on Good Friday. The onions should be planted 1 inch deep. If you are growing green onions, plant them 2 inches apart from the dry onions and put them every other onion. They will be pulled before crowding becomes an issue. If no green onions, put them 3 inches apart. Put the rows about 1 foot apart. Do not hill onions or else they may rot at the base.
Onions have shallow roots and are easily taken over by weeds. Boy, do I know about that! Late in the season the onions are almost indistinguishable from weeds unless you are ruthless at keeping them weeded. Foxtails are especially prevalent near harvest time. Many farmers do not bother weeding them – too much work…and I agree – it is a lot of work keeping them weeded.
I side dress onions with 10-10-10 fertilizer about half way through the season. Onions are watered once a week, depending on the rain, so they get 1 inch total.
Yank the green onions when they are about 6 to 10 inches long – they should be crisp. If any have stalked, use them immediately as they are not very good if they sit out. Harvest dry onions in late July or early August when most of the tops fall over. I use a potato fork to harvest them. Trying to pull them out resulted in too many broken tops. Allow them to fall over naturally; that way they produce the biggest bulb. Scallions have no bulb while green onions have a 1 to 2 inch bulb.
Try and use green onions and scallions soon after they are harvested. Store in a perforated bag in a refrigerator up to 1 week after harvest.
After harvesting the onions in the morning, let them sit in the shade for the rest of the day; unless it is raining. Put them on screens or hang them for 2 or 3 weeks. They need full air circulation in a fairly low humidity place. Many farmers put their onions in the attic where it is nice and dry. After the bulbs have dried cut their tops off 1 or 2 inches from the bulb. Discard any bulbs that have green growing from them. Store in a cool, dry place. They should last until late winter. Ideally storage temperature is 33 to 39 degrees. 40 and over they start to sprout. Some farmers put their onions in burlap sacks to store them.