The common onion (Allium cepa) may be a biennial bulb that’s closely associated with garlic (Allium satvium), shallots (A. ascalonicum) and chives (A. schoenoprasum). Onions have hollow, tubular blue-green leaves that emerge from a bulb that’s actually a modified leaf structure with many layers. A shallow network of roots extend from rock bottom of the bulb, and therefore the onion bulb itself may push partially above ground because the plant matures.

Onions have a reputation for being difficult to grow, but with a touch practice, most gardeners can roll in the hay successfully. they will be planted as seeds, as transplants (small seedling onions that have just sprouted), or as “sets” (small onion bulbs that are close to begin their second, final year of growth). it’s more common to plant onions as sets, which have an honest success rate and can become full-sized onions after several months. Since they’re in their second year of growth, onions planted from sets may send up flower stalks near the top of the season .

In colder climates, onion sets are usually planted within the spring when the weather remains cool but not frigid—above 28 degrees Fahrenheit. In warmer climates, onion sets are often planted within the fall, where they’re going to remain dormant through the winter and start growth within the spring. It takes about 3 1/2 months for the sets to mature into full-sized onions.

If growing from seeds, onion seeds are usually planted indoors a minimum of six weeks before outdoor planting time. Onion seedling transplants need outdoor temperatures above 50 degrees Fahrenheit before they will be moved into the garden.

How to Plant Onions

The best onion sets are going to be about the dimensions of a marble. Larger bulbs have a bent to bolt (set flowers) too early. If planting onions from sets, place them about 1 to 2 inches deep, spaced 2 to six inches apart. Rows should be spaced 12 to 18 inches apart.

Seedling transplants should be spaced 4 to five inches apart, also in rows spaced 12- to 18-inches apart. Seedling transplants tend to supply larger onions, since sets are still in dormancy, while transplants are already primed to grow vigorously.

Onion Care

Light

Onions need full sun—at least six hours per day—in order to properly grow. With onions, the more sunlight the higher.

Soil

Proper soil is that the key element to growing onions successfully. The soil must be extremely well-drained—even sandy—but also must have an honest deal of well-decomposed organic material in it. Onions prefer a rather acidic to neutral pH—6.0 to 7.0.

Water

Onions need regular water to support the swelling of the bulbs. Give them 1 inch of water per week, but don’t overwater or allow the bulbs to take a seat in soggy soil, since this will cause bulb rot.

Temperature and Humidity

One reason onions are considered somewhat hard to grow is that they’re cool-season vegetables but also take a reasonably while to mature (90 days or more). Further, they are doing not really begin growing well until outdoor temps have reached a mean of fifty degrees approximately. this is often why onions are generally planted from sets instead of seeds—seeds simply don’t have enough ideal growing time to completely mature.

Optimal growing conditions for onion foliage is 68 to 77 degrees Fahrenheit. this may cause rapid, full growth of the edible bulbs.

Fertilizer

Onions are fairly heavy feeders. Fertilize them every few weeks with a high-nitrogen fertilizer to support leaf growth, which can produce big bulbs (onion bulbs are literally modified leaf structures). Withhold feeding at the purpose where the onion bulbs begin to push the soil away.

Are Onions Toxic?

Onions contain a compound referred to as N-propyl disulfide, which causes a breakdown of red blood cells in dogs and cats. A pet that develops a taste for onion leaves or bulbs may suffer serious anemia.

Onion Varieties

There are three sorts of onions you’ll choose between. Onion sets or transplants purchased at an area garden center will usually be appropriate for your climate, but when buying mail-order seeds, confirm to settle on the proper variety supported your climate:

• Short-day onions will begin forming bulbs when there are 10 to 12 hours of daylight every day. They work well in southern regions where summer daylight is relatively short. Some common short-day onions include ‘Southern Belle’, ‘White Bermuda’, ‘Granex’, and ‘Cipollini’.
• Long-day onions begin forming bulbs when there are 14 to 16 hours of daylight per day. they’re good for northern climates where the summer days are relatively long. Some recommended long-day onions include ‘Walla Walla’, ‘Ring Master’, ‘Red Zeppelin’, ‘Yellow Sweet Spanish’, ‘Italian Red Torpedo’, and ‘Redwing’.
• Day-neutral onions begin to make bulbs once they experience 12 to 14 hours of daylight every day . they’re good for gardeners within the central U.S. Good varieties include ‘Red Amposta’, ‘Early Yellow Globe’, ‘Cabernet’, and ‘Superstar’.

Harvesting Onions

The time required for the bulbs to mature depends on the variability and whether or not they were started from seed or sets. But you’ll harvest onions at any stage—even seedlings thinned from a row are often used as green onions.

Onion bulbs are fully mature when about half the highest leaves have collapsed and when the bulbs’ skins have a papery feel. Bulbs allowed to stay within the ground until 50 percent or more of the green tops have collapsed will store longer.

Once you see that half the leaves have collapsed, very gently coax the remaining leaves down, without breaking them off the bulb. Then allow the bulbs to take a seat within the ground and cure for a few of days before you lift them. You’ll have better luck exhumation the onion bulbs, instead of pulling them. You don’t need to dig deep—just enough to loosen the remaining roots. Shake and ignore any loose soil and let the bulbs finish curing during a warm, dry place with good air circulation. Leave the leaves on. you’ll use fresh onions at any time now.

For storing onions, wait until the surface onion skins dry and therefore the neck—the point where the leaves meet the bulbs—starts to shrivel. Then you’ll store them during a cool, dry location, like your basement. Onions keep longer in cool temperatures (under 40 degrees Fahrenheit) but shouldn’t be allowed to freeze. Store onions in mesh type bags or by braiding the tops together and hanging; just confirm they’re getting good air circulation

Common Pests and Diseases

• Rot: In damp soils, you’ll encounter neck or stem rot or bulb rot. Avoid rot by ensuring there are good soil drainage and air circulation.
• Splitting: Bulbs will split or double if the soil is allowed to stay dry while the bulbs are forming.
• Thrips: These small, yellowish-brown flying insects prey on leaves and may cause twisting and curling. Repeated attacks cause the plant to prevent growing, so bulbs don’t mature. Plant resistant varieties and don’t plant onion near grain crops. Neem and insecticidal soaps provide temporary control.
• Onion root maggots: These larvae hatch from eggs laid by brown flies near the bottom of onion plants. The hatching maggots burrow into the stems, feeding on the plants below the soil and eventually killing the onions. Rotate plants yearly to avoid infestation. Covering new seedlings will prevent eggs from being laid. diatomite is additionally effective.

Growing Onions from Seed

If planting onions from seeds, plant them indoors in trays crammed with the seed-starter mix a minimum of six weeks, and the maximum amount as 12 weeks, before outdoor planting time. Place the tray under artificial grow lights for 10 to 12 hours every day. Keep the potting mix damp but not soggy. When outdoor temperatures are routinely above 50 degrees Fahrenheit, transplant the seedlings into the garden.

DAYLIGHT HOURS AND ONION BULB FORMATION

• Onion bulb development is very hooked in to daylight. Onions quit forming leafy tops and start to make bulbs when the daylight every day reaches a particular length. the quantity of daylight needed for an onion to start forming a bulb varies by variety.
• Be reminded that the length of daylight in your a part of the planet varies throughout the year depending upon latitude. The variation in daylight is caused by the lean of the Earth’s axis of rotation because it makes its year-long ecliptic journey round the sun. At the solstice occurring about June 20–22, the North Pole is tilted toward the sun, then the hemisphere has days ranging in duration from just over 12 hours within the southern portion of the Northern Hemisphere—closest to the equator–to 24 hours at the North Pole within the Arctic Circle . (At an equivalent time within the hemisphere days home in duration from slightly below 12 hours within the northern portion of the hemisphere to no daylight at the South Pole . This is, of course, reversed at the solstice occurs about December 20–22. At the equinox occurring about March 19–21 and again about September 22–23, the poles are neither tilted toward nor faraway from the sun, and therefore the duration of each day is usually about 12 hours everywhere the world .)
• In each hemisphere, the upper the latitude (or distance from the Equator), the longer the amount of daylight during the summer and therefore the shorter the amount of daylight during the winter.
• Because location or latitude determines day length, some onion varieties aren’t fitted to some locations.
• Short-day onions require just 12 to 14 hours of daylight every day to make bulbs. This happens within the southern regions of the hemisphere to not greater than latitude 36°N.
• Intermediate-day onions require 13 to fifteen hours of daylight every day to make bulbs. Intermediate day onions grow best between latitudes 35° to 38°N–but many are adapted for production to latitude 42°N.
• Long-day onions require 14 to 16 hours of daylight every day to make bulbs. Long-day onions do the simplest north of the 36th parallel or latitude 36°N.

Leaf, root, and bulb development occurs in cool temperatures between 55° to 75°F.

TEMPERATURE AND ONION BULB FORMATION

• Onion seeds sprout usually within 7 to 10 days. The minimum temperature for sprouting is 55°F (12.8°C); because the soil temperature increases from 55°F to 75°F the share of seeds sprouting will increase and therefore the time to emergence decreases.
• Onions are adapted to a good range of temperatures and are frost tolerant. Leaf, root, and bulb development occurs in cool temperatures between 55° to 75°F. Optimal onion leaf growth occurs at 68° to 77°F (20° to 25°C). Once bulbing has begun onions easily tolerate temperatures above 75°F.
• Bolting—the setting of seed and cessation of bulb development–is driven by temperatures between 40° to 50° (7.2° to 10°C). (Plant variety, planting date, plant size, temperature, and duration of temperature all factor into whether and when onion bolts.)