How to grow Onion?

The onion is one of the essential kitchen ingredients that no cook can do without.

Videos

Onion History

The onion probably originated somewhere in central Asia, but has been cultivated by every major civilization from the Egyptians, Greeks and Romans onward. It is now one of the most important flavorings for people all around the world.

Apparently the word onion comes from Latin meaning one, because it only produces one bulb, unlike the related garlic and shallot.

Soil Preference

PH (min/max): 6.0 - 7.5
PH Ideal (min/max): 6.8 - 7.0

Onions don't need a lot of nutrients, but they aren't very efficient feeders (their roots are weak and shallow), so you have make sure they have plenty available. For example, they only need about 150 pounds of nitrogen per acre, but you may have to add 300 pounds for them to get even that much.

Onions do best in a loose, rich, moisture retentive soil with lots of organic matter. They don't like compacted, heavy, dry, acid, salty, or poorly drained soils (their roots may rot if it is too wet).

For more information on soil [click here.:Understanding Your Soil#SoilTexture].

How to care for Onion?

Onions should grow as fast as possible, so by the time the day length is right for bulbing--they will have stored enough food to produce large bulbs. This means spacing them properly and giving them all the nutrients and water they need.

The most important thing to remember about growing this biennial is that it is day length sensitive. It is programmed to produce bulbs when the appropriate day length arrives, no matter how big or small it is. It is your job as a gardener to get the plants as big as possible before the onset of bulbing. To do this you must use a variety that is appropriate for the day length of your location. You should also plant them as early as is safe, so they can put on the maximum amount of vegetative growth before bulbing.

Planting: There are several ways to grow onions. You can use seed, transplants or sets. All of these are fully hardy and can be planted as soon as the soil is workable in spring. When you first try growing onions it isn't a bad idea to use two different planting methods at the same time to see which works best for you.

Seed: Growing your own Onions from seed gives you the greatest choice of varieties. The problem with Onion seeds is that they are slow, growing only half as fast as lettuce, so you have to start them early. Onion seed is also the shortest lived of all common vegetables, so it is important that they are fresh.

You can use seed to grow sets or transplants, or to sow directly in the ground.

Onion sets: These are small onion bulbs (3/8" to 3/4" in diameter) grown in crowded conditions so as to induce premature [bulbing]. They are the easiest way to grow onions, as you don't have to worry about [germination], and actually start with a small bulb.

Buying sets: Every spring, sets are readily available in every garden center, so they are probably the common way to grow onions. The biggest problem with buying sets is that there are very few varieties available (some packages don't even say what type they are). However, if you buy them locally they should work well.

Growing sets: This is easier than you might imagine and has the advantage of letting you grow whatever variety you want.

Transplants: Using transplants gives you the largest onion bulbs and produces them a lot faster than by direct sowing. You can start these yourself in mid winter or buy them mail order.

Onions are quite drought tolerant, but a lack of water makes the bulb smaller and more pungent. For best flavor and largest bulbs you must keep the soil moist at all times, so there is no interruption in growth.

Low nitrogen. Moderate potassium. Moderate phosphorous.

Onions don't need a lot of nitrogen, but they do like potassium and phosphorus.

Seed Viability: 1 - 4 Years

Germination Percentage: 70.0

Onions are cross-pollinated by insects but this isn't usually a problem as there are no close wild relatives and most people don't let their onions flower.

Onions are biennial and will flower in the spring of their second year. In mild climates you can leave the bulbs in the ground over the winter, but in cold climates you will have to store them inside and re-plant them in spring.

Use the best onions you have for seed. Larger bulbs produce larger flowers (they sometimes get to 4 feet in height) and more seed.

Make sure the flower heads are thoroughly dry before collecting seed, then remove the seed from the head and dry it thoroughly before storing. Onion seed doesn't remain viable for very long; 2 or 3 years at the most.

Sun: min. 6 hours daily

Full sun.

Conditions:Cold, Cool, Warm

Season:Short Season, Long Season

Before storing any bulbs you should examine them carefully. The papery outer skin should be in good condition, there should be no bruising and the neck should be dry and papery. If the neck is still thick it didn’t mature properly and won’t store very well. These bulbs should be used first.

Store the bulbs in mesh bags (old panty hose works well), or make Onion braids. Keep them in a cool, dry place at 32 to 50˚ F and 60% humidity. Excessive moisture can encourage sprouting.

Onion braids look great hanging in the kitchen, but it is too warm and dry to store them there for any length of time (they will dry out). You could make small braids and bring them into the kitchen as you need them.

Storage Req: Cool
Storage Temp: 32-50°F
Storage Length: 1-180 days

Problems

Tip burn

A deficiency of potassium may cause the tips of older leaves to die back.

Day Length

Onions don’t always perform as expected because of their sensitivity to day length. The days must be of a certain length to induce bulb formation and different varieties need different day lengths. If a long day variety is planted where the days are too short, it will grow well enough, but may never produce bulbs. If you plant a short day variety where the days get too long, it will bulb prematurely and the bulbs won’t get very big.

Short day: 11 to 12 hours

Intermediate day: 12 to 14 hours

Long day: 14 to 16 hours

Very long day: 16 or more hours

Day neutral: A few varieties are day neutral.

Generally short and intermediate day varieties are grown below 40 degrees latitude, long day types above this line.

Bolting

Onions will sometimes [bolt] instead of [bulbing], or bolt while they are bulbing. This usually happens because the plants were [vernalized]. For a plant to be vernalized it must be at least ¼˝ in diameter (smaller plants aren’t usually affected) and must be exposed to temperatures below 50˚ F for two weeks. When warmer weather returns, the plant thinks it has gone through a winter and so sets about following its destiny, which is to produce seed.

Bolting doesn’t affect edibility, you can just remove the woody stem core when chopping the bulb. However it causes the plant to devote some of its energy to flowering, so the bulb doesn’t get as big as it could have.

Bulbing

The onion bulb is a food storage organ comprised of layers of specialized leaves. Bulbing occurs when the plant stops producing new leaves and starts to store food in the leaves it already has. This causes their bases to swell and form the bulb. When the bulb is mature, all of the food has been transferred from the rest of the leaves, so they wither, fall over and die.

The most important thing to remember about growing this biennial is that it is day length sensitive. It is programmed to produce bulbs when the appropriate day length arrives, no matter how big or small it is. Your job is to get the plants as big as possible before the onset of bulbing. To do this you must use a variety that is appropriate for the day length of your location. You should also plant them as early as is safe, so they can put on the maximum amount of vegetative growth, before bulbing.

Growing Sets

Growing your own Onion sets is easier than you might imagine and has the advantage in that you can grow whatever variety you want. The other advantage is that the bulbs will grow larger in one season if started from sets than if they are started from seed.

1. Simply scatter the seed on a prepared bed 1/4˝ apart and cover with 1/4˝ to 1/2˝ of sifted soil/compost.

2. Don’t feed the plants and go lightly on the watering. Because they are growing so close together they will crowd and stunt each other.

3. When the tops turn brown, dig and dry the small bulbs for at least 10 days.

4. Store your sets in the fridge or root cellar (below 40˚ F). Sets with a diameter of less than 1˝ are the best, as they are less likely to bolt.

Onion Types

Storage, Red

Red onions are very sweet and can be eaten raw. They also add a beautiful color to any dish!

Boiling

Boiling onions are small, white and round with a 1-1 1/2" diameter. The flavor is mild, and they are used, as their name suggests, primarily for boiling.

Pearl

The sweet onions are low in sulfur and high in water, which gives them such a mild flavor they can be eaten raw. They also have thin skins and so don't store very well.

Sweet, Red

The sweet onions are low in sulfur and high in water, which gives them such a mild flavor they can be eaten raw. They also have thin skins and so don't store very well.

White

White onions are a dry onion with a pure white skin, and mild sweet taste. This onion is commonly used in Mexican cooking, and can be used fresh to provide a sweet and sour flavor, or used sauteed to a dark brown color.

Storage, Yellow

The yellow onions have a papery-brown skin and yellow center. They are a drier onion and have a strong flavor.

Cipollini

Cipollini onions are small to mid size with flat tops and bottoms. The sweet onions are low in sulfur and have more residual sugar in white and yellow storage onions. They are best known for their roasting characteristics because of their sweetness in flavor. They also have thin skins and so don't store very well.

Sweet, Yellow

The sweet onions are low in sulfur and high in water, which gives them such a mild flavor they can be eaten raw. They also have thin skins and so don't store very well.

Specialty

Specialty Onions are unique in their own right. Combo Packs of onions contain multiple allium plants, including leeks.

Green (Scallions/Bunching, Spring)

Green onions do not form a bulb, but instead are grown for the green tops, which are milder than most onions.

Pests

Thrips
Aphids
Cutworms
Onion Maggot
Slugs and snails

Diseases

Onion Smudge
Rust
Scab
Damping Off
Downy Mildew
Fusarium Bulb Rot
Onion Leaf Blight
Onion Neck Rot
Onion Purple Blotch

Get your Garden

What's Smart Gardener ?

The easiest way to plan, grow and harvest your own food....

It's an online vegetable garden planner for anyone who wants homegrown, healthy and tasty food to be part of their lifestyle...while having a busy life.

Find out more...

Join Now

Try it out!
Explore Maggies Garden...