Onions are placed into two different categories. There are long day onions and short day onions. Long day onions tend to grow better in the Northern states and require about 15-16 hours of sunlight to produce bulbs. Short day bulbs work well in the Southern states and need about 12 hours of sunlight to produce bulbs. When shopping for onion varieties to grow, they will be labeled with an L for long day, and s for short day.
The other main thing you need to know about onion varieties is how they grow. We tend of onions as bulb onions, but there are also perennial onions, like leeks, chives, nest onions, and bunching onions.
Here are onion varieties to grow in a home vegetable garden:
Shallots (Nest Onions):
French shallots, Red shallots, Echalion shallots, Dutch yellow shallots
White Portugal, White Spear, Ebenezer, Tokyo Long White
Beltsville Bunching, Japanese Bunching, Deep Purple, Evergreen Hardy White, Evergreen White
Winter Onions (planted in winter prior to growing season):
Egyptian, Hill, Walking
Disease Resistant Onions:
Texas Grano 1015Y, Crystal Wax
Yellow Globe, Copra, Sweet Sandwich
Burgundy, Red Wethersfield
Vidalia, Sweet Spanish, Bermuda, and Walla Walla
Preferred Growing Conditions
Depending on what type of onion you’re growing, will depend on the sunlight they require. Provide onions with 12 – 16 hours, depending on long day or short day onion.
The best soil for onions has organic material and neutral pH. (If your onions are too strong, the soil may be too acidic.) Onions like well drained soils, and the organic matter in the soil helps. And, we want our onions to be happy, right? Oh, and while we are talking about what onions like—they dislike weeds. Keep their growing area weed free.
Prior to planting, work in a little compost into the soil. If you don’t have a compost bin, just pick up a soil amendment to help condition the soil. It helps to work amendments into the soil the fall prior to planting season. But, it’s better to be late than never. So, add it when you can.
How to Plant Onions
Grow onions from seeds, transplants, or sets. Sets are small onion bulbs.
Growing Onions from Seeds
Plant onion seeds about 3/8 inch deep and 1/2 inches apart. Rows should be about 15 inches apart. Once seedlings emerge, then to about every 3inches.
Growing Onions from Transplants
Transplants do not have a bulb, yet. But, they’re a great way to plant bulb onions. Plant transplants 1 inch deep. Space transplants about 4 inches apart. Rows are still about 15 inches apart. If you are not planning on harvesting the bulbs, and just using them for green onions (the tops) you can plant them closer together.
Growing Onions from Sets
Planting sets are the easiest way to grow bulb onions. It decreases harvest time, too, since they are started onions. Plant sets about 1 ½ to 2 inches deep in 15 inch rows. You can plant these pretty close together and thin out by harvesting the green onions, and let the others grow to bulbs.
Companion Plants for Onion
Growing these companion plants around onions will be helpful: carrots.
Some plants actually are bad to the health of onion plants. Avoid these plants around onions: beans, peas, and parsley.
Maintaining Onion Plants
Onions like more water initially as they grow. As they mature, onions do not require as much water. Depending on how much rain you get, they may be okay with just rainwater. Just make sure they get some kind of water every 5-7 days.
Mulch will help maintain the right soil moisture level and reduce weeds. Remember, onions don’t like weeds. Weeds and onion, both, compete over the same soil nutrients. When weeding, be careful not to disturb the onion’s root system.
When to Use Organic Fertilizer
Fertilizer may not be necessary; especially, if quality compost was worked into the soil prior to planting. What does work well for onions, is a natural mycorrhizal fungi root builder. Mycorrhizal fungi attaches itself to the roots, and helps the roots absorb water and soil nutrients. So, save your organic fertilizer for nearby tomatoes.
Harvesting Bulb Onions
If planted from sets, bulb onions are ready in late summer. They take about three months to be ready for harvest. You know bulb onions are ready for harvest when the plants begin to yellow. The onion bulbs will also swell a bit. The tops of the plants need to be broken to start the ripening process and keeps them from growing anymore. Harvest before the onion begin to product flower stalks.
Some larger farms actually roll a barrel over the tops of the plants to knock them down. I am thinking, this could be a great party. You know, like a grape crushing festival! Just don’t hop in the barrel.
After about a week after the tops are broken, they are ready for harvest. Onions should be harvested in the morning, but avoid any morning dew on them. Lay them in row to cure or air dry for a few days. But place them in the shade. The onions can actually sunburn.
Harvesting Green Onions
Most of the time, green onions are immature bulb onions, unless growing a specific variety like bunching onions. Green onions can be harvested when they are 5 inches tall. The taller they get, the stronger flavor they will have. If you planted from sets or transplants, they will be ready for harvest in about a month.
Onions will need to be cured a total time of 2 weeks to a month. Store onions in a cool place with good air flow. Sweet onions will store for about two months. Stronger flavored onions will last a little longer.
Onion Pests and Diseases
Common pests and disease for onions are: thrips, onion maggots, and soil borne diseases. Your best bet to reduce these concerns is to rotate the location of the onion crop every year.