How To Grow Onions

Onions are one of those vegetables that seem to fit into any dish or food universally. The question every new gardener asks is how to grow onions.

This vegetable was a valuable remedy in ancient times and today it is still considered a healthy food. Its medicinal properties are backed up by years of research and usage.

So if you are planning to add onions to your garden, you are on the right path. In this article, we will tell you everything you need to know about onions.

TABLE OF CONTENT

1. Onion Plant Description
2. What are Onions
3. History of Onions
4. How to Grow Onions
5. Best Onion Varieties
6. Onion FAQ

Onion Plant Description

Common Name: Onion

Scientific Name: Allium cepa

Growing Season: Cold season – Spring/Fall

Transplant or Direct Sow: Direct sow

Sunlight: Full Sun

Hardiness Zones: Zones 5,6, and 7

Germination Time: 7-10 days

Water: Once a week. 1 – 1/2 inches of water per week

Temperature: 40°F; the best soil temperature is 75°F.

Humidity: 65 – 70%

Soil: Loose soil with pH 6.0 – 7.0, and high organic matter.

Average Days To Harvest: 90-175 days

Fertilizer If Needed: Compost, high nitrogen fertilizer.

Best Onion Companion Plants: Beets, lettuce, strawberries, summer savory, and tomatoes.

Worst Onion Companion Plants: Beans, Asparagus, Sage, garlic, leeks, shallots, chives, and scallions

Common Pests: Onion thrips, maggots, bulb mites, and eelworms

Diseases: Fusarium bulb rot, Smut, Onion leaf blight

What Are Onions?

Onions are an herbaceous biennial plant that belongs to the Allium subfamily under the Amaryllidaceae family. It is the most widely cultivated of the Allium genus and is known botanically as Allium Cepa.

The name ‘Onion’ is widely used for several other species in the Allium genus, including the Japanese bunching onion (Allium fistulosum), the tree onion (A. × proliferum), and the Canada onion (Allium canadense). But the Allium Cepa is differentiated from cultivation and is commonly known as the bulb onion or common onion.

Even though the vegetable is a biennial plant, it is generally grown as an annual and harvested during the first growing season.

The common onion comes in different shapes, sizes, and colors. They are peculiar for their pungency when cut, which is a result of their sulfur-rich volatile content.

The bulb onion grows up to 75–180 cm (2.5–6 feet), with a cluster of greenish-white flowers. The bases of the plant swell to form the underground edible bulb.

Generally, Onions are lacking in essential nutrients, it is made up of 89% water, 1% protein, and around 4-7% carbohydrates. But what it lacks in nutrients, it more than makes up in its unique flavor. It makes for an exquisite flavor in dishes such as stews, roasts, soups, and salads and is also served as cooked vegetables.

It has been proven to inhibit the growth of cancer tumors.

Its consumption has been associated with a reduced risk of cancer, heart disease, and diabetes because of its high level of phenolic and flavonoid compounds with high antioxidant activity. In general, onions with greater pungency have higher antioxidant activity than milder types

History Of Onions

Onion is one of the oldest cultivated vegetables in the world. Even though the exact date and place of origin cannot be determined, evidence traces its origin to more than 5000 years ago somewhere in Central Asia.

Long before the documented history of man, some scientists believe that Onions were already part of the human diet as early as the Bronze Age.

In ancient Egypt, Onions were grown as far back as 5,500 years ago. It was delicacy as well as a sacred totem that they worshipped. They believed that its concentric rings represented eternal life, hence, they buried the dead with it. Onions were also an important part of the famous Egyptian mummification process.

Around 3,500 BC, Onions cultivation became more systemic and organized.

It became popular with the Babylonians, Hindus, and ancient China for being easy to grow on any kind of soil, with little or no care as to the weather and can be stored over the winter season.

Because of the diverse purpose of the vegetable and its value, its popularity quickly spread. It became heavily present in record books of the 1st millennia BC and early centuries of AD.

The Christain Bible recorded it as a source of food for the Israelites in Numbers 11: 5.

In Ancient Greek, athletes and soldiers alike consumed Onions in large quantities. They believed it contained special power by the gods so they consumed both raw and cooked, and used the juice as rubbing oil. Romanians and their Gladiators were not left behind.

The Romans spread the popularity of the Onions as they conquered cities from Italy to Spain, the Balkans, the majority of Central Europe, and England.

After the fall of the Roman empire, a great famine hit Europe. The main sources of food for the entire population were beans, cabbage, and onions. The value of onions at that time became more than money, as they served as both a source of food and a medicinal remedy.

With the dawn of the Golden Age of Sail, new trade routes emerged. Onions were distributed to the ends of the earth.

How to Grow Onions – 5 Easy Steps

1. Where To Grow Onions

It is true that onions can do well in any weather or place, but you don’t want to take them for granted. Picking out the right spot is as important as getting the right seedlings.

Common onion or bulb onion as it is known grows best in areas where there is full sunlight and the soil is well-drained.

Bulb onions love their full sun whereas, Green onions can do just fine in a partially shady spot, where it can get enough sunlight but not too much.

Every Onion demands full sunlight, 10-12 hours of sunlight is best. But if you decide to grow them in a shade, you should be aware that your plant is more susceptible to diseases and pests.

Now that you have an area with full sunlight, the right soil requirement is what you should check out.

Onions blossom well in well-drained, loose soil with a pH between 6.0 and 7.0, and high organic matter. In any case, if the soil is not well-drained, you can grow them in mound beds or raises.

Growing onions in heavy clay soil is a no-no, not if don’t want to stunt the development of the bulbs. Sandy soil is best for growing onions in sets, while Loamy is good for seeds and seedlings.

The ideal temperature for growing onions is 75°F, but onion seeds typically germinate at temperatures above 40°F.

2. How to Grow Onions

To get a headstart, you should consider ‘sets’, they mature faster and is ideal if you live in a short growing season region. Seedlings will need more time to produce bulbs than sets.

If you stay in an area with a long growing season, and you can afford it, you can go for the seeds. You have a wider range of varieties to pick from in seeds.

Seeds can be started 3-4 weeks indoors However, before transplanting the seedling or in cases of direct seeding to the ground, the soil and area of the planting should be prepared. Loosen the soil and remove all lumps, stones, and roots.

Add well-aged compost or a commercial organic planting mix to the planting bed before planting. Turn the soil under.

Thin seedlings after the initial sprouts; thin again for bulb onions from 4 to 6 inches (10-15cm) apart. You can use the thinnings as green onions.

Onions, generally, are temperature-sensitive plants while some varieties are day-length sensitive.

Common onions are day-length sensitive, their only sprout after it must have surpassed a minimal number of daylight hours. There are three main categories under this.

Short-day onions: they are recently developed varieties of onions. They only need 11-12 hours of daylight to encourage bulb formation. They are planted in mild-winter areas in autumn which brings the bulb formation to early spring.

Intermediate-day types: Southern European and North African varieties are often put in this category. They require between 12–13 hours of daylight to encourage bulb formation.

Long-day onions: Traditional European onions are found in this category, they only yield bulbs after surpassing 14 or more hours of sunlight.

Onions require plenty of sunlight but they are typically cool weather plants, they can bolt under hot temperatures or unfavorable conditions.

The soil should be kept moist until the plants begin to mature and sprout. Moist enough that the onions do not split from dry soil, but not too wet that the bulbs rot.

To maintain the soil moisture in the warm weather, you can cover the area with 8 to 10 inches of mulch. When the leaves start to get brownish-yellow, it is safe to let the soil go dry. An inch of water per square foot per week is enough for an onion unless it is a dry season.

Be sure to keep the planting beds free from weeds. To hasten the bulb growth, bend the stalk 2-3 weeks before the harvesting season. At this time also, reduce the watering quantity so as to avoid rotting of the necks.

A little side notes: if you have plans to over-winter your onions and harvest the second season, you should consider heavily mulching it.

Planting sweet potatoes near onions will be a plant murder as both will be prone to wireworm attacks. Beans are a better companion, the bean roots introduce nitrogen to the soil.

Furthermore, if you want your onions to yield big bulbs, you should constantly nourish them as they are heavy feeders.

3. How To Plant Onions

Onions can be grown from seeds, seedlings, or sets. But it is better grown from the sets. What is set? You may ask.
Onion sets are small bulbs are have been harvested prematurely in the previous season and then stored over the long winter.

Seeds: Seeds can be started indoors 4 to 6 weeks before transplanting, or direct sown in the garden when the soil temperature is at least 40°F (4.4°C). Plant the seed 12mm deep.

At 70°F (21°C), the seed germinates in 7 to 10 days but takes longer in cooler soil. Seedlings should be spaced 1 to 2 inches (2.5-5cm) apart in rows 12 to 18 inches (30-45cm) apart; bulb onions should be spaced 4 to 6 inches (10-15cm) apart.

Seedlings: You can start your own seedlings indoors or you can buy from the store, this depends on your budget and time.

For your seedlings to settle into place, plant them a bit higher than the surrounding soil. Seedling transplants should be spaced 2 to 3 inches (5-7cm) apart in rows 12 to 18 inches (30-45cm) apart. Thin to 4 to 6 inches (10-15cm) apart or more to allow for bulb development.

Sets: Plant sets 1 to 2 inches (2.5-5cm) deep. The plant should be placed pointed side up. Sets should be 2 to 3 inches (5-7cm) apart in rows that are 12 to 18 inches (30-45cm) apart.

Allow for bulb development by thinning to 4 to 6 inches (10-15cm) or more apart. Sets larger than ¾ inch (19mm) in diameter may go to seed before developing bulbs, these are best grown as green onions.

Tip: Onion sets are best planted in the spring when the ground is workable and the temperature is stable above 28°F (-2°C). This is usually around late March or April.

Apply nitrogen fertilizer at planting time. Before planting, many organic gardeners will add an inch of compost to the bottom of each row. Alternatively, dig a trench in the soil about 2 inches deep and 3 inches wide, then fill it with about an inch of compost.

4. How To Harvest Onions

Onion vegetables take their sweet time to get ready for harvest, and they let you know when they are ready by the yellowing and falling over of the foliage.

You can speed up the process by stomping on the top. Now you can loosen the soil surrounding the bulb to hasten the drying.

Then when the foilage has completely turned brown, you can pull out the onion. You are to pull gently but firmly to avoid bruises that lead to rot.

Bulb onions can be harvested when bulbs are 1 to 2 inches (2.5-5cm) in diameter

Cut the roots, Trim the tops back to 1 or 2 inches (but leave the tops on if you are planning to braid the onions together). You can snip the leaves for dishes throughout the season.

Tip: if you plan to store your onions for long, you should harvest by late summer when the weather is dry enough for proper curing

5. How To Store Onions

To get your onions to last well into the winter and all year long, you will want to cure them first before storage.

After your bountiful harvest, cure your onions by leaving them outdoors to dry for a few days. Spread them on a mat or mesh that is not touching the ground. Be careful not to expose them to direct sunlight to avoid sunscald.

You can also cure them in the garden, but be sure to separate the root and all from the soil or they may start sprouting again. Also, cut away the tops of stalks 1½ inches from the bulb if you do not plan to braid the stalks.

Then dry the bulbs until their skin becomes scaly or papery. Curing takes usually 2-10 days outdoors or two weeks indoors.

The Best Ways To Store Your Onions

1. Pantyhose: this is one of the most cost-effective to store onion using a nylon pantyhose. The synthetic nylon helps to repel moisture and allows good airflow.

2. Screen: this method can last for 5-8 months. It is a flat mesh screen used to store onions in your root cellar or storage room.

3. Perforated plastic bag: is best for storing green onions. Keep in a vegetable crisper of the fridge. This can last for 3-4 weeks.

4. Paper bag: it is not only a convenient method of storing onions, it is also environmentally friendly.

What Are The Best Onion Varieties?

As stated earlier, onions have different varieties depending on the day length sensitivity. The three main categories are:

Best Long Day Onion Varieties

Yellow Sweet Spanish – Large, round shape; yellow-white.
First Edition – High-yielding, stores well, flavorful, creamy-yellow
Red Wethersfield – Long storage, white flesh, red-skinned
Aisa Craig, Walla Walla – Huge bulbs
Buffalo – They can be harvested early
Red Florence – Oblong shape

Best Short Day Varieties

Stuttgarter – Early maturity – flat shape – sold in sets – yellow
White Bermuda – Extremely mild – thick flat bulbs – white
Red Burgundy – Table onion – mild – sweet white inside – short-term storage life.
Hybrid Yellow Granex – Sweet -mild – Vidalia type – good storage life

Day Neutral, Intermediate Varieties

Candy – golden – thick-flesh – jumbo bulbs – stores well
Red Stockton – large – red-ringed – white-flesh bulbs
Super Star – large – sweet – white bulbs

Onion Frequently Asked Questions

1. Can You Plant a Sprouted Onion?
2. Which Is The Best Variety Of Onion To Grow?
3. Onion Pest and Diseases
4. Onions Last How Long?
5. How Long Does An Onion Take to Grow?
6. When To Water Onion Plants?
7. How Often Should An Onion Be Watered?
8. How Do I Know When My Onions Are Ready to Harvest?

Can You Plant a Sprouted Onion?

Even though you will not get more onions out of it, Yes, you can plant sprouted onions. You can, however, get green sprouts from it.

Which Is The Best Variety Of Onion To Grow?

This depends on your region and it’s daylight lenght. If you live in area with short day light, choose short day Onions but if you have the advantage of long day time, you can go for the it.

In a case that you are not so sure, it is best to go for the day-neutral variety.

Common Onion Pest and Diseases

Just like every other plant, onions are prone to pest and diseases. Here are some common onion pest and diseases:

Pest
Nematodes
Stem and bulb eelworm
Thrips
Onion fly or maggot.
Diseases
Fusarium bulb rot
Smut
Onion leaf blight
Onion smudge
Downy mildew
Damping off.
Purple blotch.
White rot (Sclerotial rot)
Pink root rot.
Black mould.

How Long Do Onions Last?

Onions can last as long from 8 months to 1 year, depending on the storage method.

How Long Does An Onion Take To Grow?

It takes 90- 175 days, for an onion to fully mature.

How Often Should An Onion Be Watered?

It is best to water an onion once a week, ideally, one inch of water. However, it can be watered more during hot weather.

How Do I Know When My Onions Are Ready To Harvest?

You can know if your onion is ready for harvest when the top of the plant starts falling over.

Final thoughts

Growing onions can be fun and scary at the same time, however, it is an amazing addition to your farm or garden. We wish you a pleasant gardening experience, we will be here to answer any questions.

If you enjoyed this in-depth article then check out how we grow spinach or what I am growing this year. Have fun gardening!