How to Grow Onions: A Step-by-Step Guide


Onions are a common vegetable found in most grocery stores. They are relatively easy to grow and can be planted from seeds or transplants.

There are many different types of onions, each with their own flavor and color. Onions must be planted in the spring and should be harvested before the summer heat arrives.

Common Name Onion
Botanical Name Allium cepa
Family Amaryllidaceae
Plant Type Biennial, vegetable
Size 12-18 in. tall, 6-12 in. wide
Sun Exposure Full sun
Soil Type Loamy, well-drained
Soil pH Neutral
Bloom Time Summer
Hardiness Zones 5-10 (USDA)
Native Area Asia
Toxicity Toxic to pets

Tips for Keeping Your Plants Healthy

  • Onions are relatively easy to grow, but there are a few things you can do to ensure your plants are healthy and productive.
  • Here are a few tips for growing healthy onions:
  • Fertilize regularly. Onions are heavy feeders and will benefit from regular fertilization.
  • Apply a balanced fertilizer every couple of weeks or so, or side dress with compost or manure once the plants start to grow.
  • Water regularly. Onions need consistent moisture to prevent them from bolting (going to seed). Water deeply and evenly, especially during dry periods.
  • Mulch around the plants. This will help keep the soil moist and cool, which is ideal for onions.

Lighting and Temperature

Onions need full sun to grow properly and produce a good crop, so make sure to choose a spot in your garden that gets at least six hours of direct sunlight each day.

The ideal temperature for growing onions is between 65 and 70 degrees Fahrenheit, so if you live in an area with cooler summers, you may want to start your onions indoors about six weeks before the last expected frost date.


Onions need full sun to partial shade and prefer loose, well-drained soil with a neutral pH. They also require consistent moisture, especially during bulb formation.

If your onions are getting too much or not enough water, it will affect the taste. Overly wet conditions can cause the bulbs to rot, while drought stress will make them taste strong and bitter.


Onions require a lot of nitrogen to grow properly. You can use either a synthetic fertilizer or manure.

If you choose to use manure, make sure it is well-rotted so that it doesn’t burn the roots of your onions.

You should fertilize your onions every few weeks during the growing season.


Pruning the onion plant is essential to its growth. To prune, cut the green onion tops off about an inch from the bulb.

This will allow more nutrients to go to the bulb itself, making it larger. It also makes for better air circulation around the plant, which prevents fungal diseases.


Onions need about an inch of water per week. They should be watered at the base of the plant, rather than from above to avoid getting water on the leaves.

This can lead to fungal diseases. Water in the morning so that the leaves have time to dry off before nightfall.


Size is an important factor to consider when planting onions. They can be planted as close together as four inches, but will need more space if they are going to bulb.

Bulbing is determined by the amount of daylight the plant receives; shorter days cause the onion to form a bulb.


Flowering occurs in the second year of growth and is triggered by day length. If you want your onions to flower and set seed, select a site that receives full sun for at least six hours each day.

The ideal soil temperature for germination is between 68-86 degrees Fahrenheit.

Common Pests and Plant Diseases

Onions are a member of the Allium family, which also includes garlic, chives, and leeks. Like other Allium species, onions can be susceptible to certain diseases and pests.

For example, humid conditions can lead to stem or bulb rot, and onions may split if the soil is allowed to dry out. Thrips are tiny flying insects that feed on foliage, causing leaves to coil and twist.

Brown flies lay their eggs at the root of onions, where the larvae hatch and begin to feed on the bulbs. To prevent these problems, it is important to plant onions in well-drained soil and to choose resistant varieties.

Neem oil and insecticidal soaps can provide temporary relief from pests. By following these simple guidelines, you can ensure a healthy onion crop.

Propagating Onions

Spring is the best season to start growing an onion from the leftovers. Fresh onions should have the top cut off and the skin removed, about one inch.

On a level surface that has been dried for at least a day, place the piece’s cut side to dry. In a container filled with damp, soilless potting mix, with the bottom (root) pointing down. Add soil to the top in a light layer.

Your container should be placed in an area with good indirect lighting. Keep the soil moist but not soggy. You’ll start seeing greener leaves emerge from the ground in two weeks.

At the same time, the roots are growing. You’ll know the roots are ready when they’re about an inch long. Once they’ve reached this point, you can transplant them into your garden beds or larger pots.

When done correctly, this technique can help you expand your onion harvest and add value to otherwise lost produce.

Types of Onions

There are three main varieties of onions: short-day, long-day, and intermediate-day. Short-day onions form bulbs when there are 10-12 hours of daylight per day.

They are best suited for locations in the south where the days are shorter. Some of the most popular short-day onions include Cipollini, Southern Belle, White Bermuda, and Granex.

Long-day onions, on the other hand, start to form bulbs after 14-16 hours of daylight each day. They do well in northern climates where summer days can be quite lengthy.

Walla Walla, Ring Master, Italian Red Torpedo, Yellow Sweet Spain, and Redwing are some of the most common long-day onions.

Lastly, intermediate-day onions fall somewhere in between short-day and long-day onions in terms of when they form bulbs (usually 12-14 hours of daylight).

Intermediate-day onions are a good option for those who live in regions with moderate climates. Some examples of intermediate-day onions include Spring Wonder, New York Early White, and Candy.

How long does it take for an onion be ready to pick?

Onions are a staple in many cuisines around the world, and they can be used in a variety of dishes, from soups and stews to salads and stir-fries.

But how long does it take for an onion to be ready to pick? The answer depends on the type of onion. For example, spring onions are typically harvested after just 60-70 days, while sweet onions can take up to 120 days to reach maturity.

Storage onions, which are designed to be kept for long periods of time, usually take even longer to mature, often reaching 140 days or more.

Of course, temperature and growing conditions can also affect the length of time it takes for an onion to be ready to harvest. In general, though, most onions will be ready to pick within 100-120 days.

How long does it take an onion to complete its life cycle?

Onions are one of the oldest cultivated crops in the world, and their popularity is easy to understand. They are versatile, easy to grow, and have a long shelf life.

Onions are also a relatively low-maintenance crop, and they have a relatively short life cycle. Most onions will be ready to harvest within two years of planting.

Once harvested, onions can be stored for several months, allowing gardeners to enjoy the fruits of their labor well into the winter months.

Consequently, onions are an excellent choice for both novice and experienced gardeners alike.

How do you get your onions to grow bigger?

Onions are a staple in many kitchens, and home growers often want to produce larger onions than what they can find at the store.

While there are a number of factors that affect onion size, there are a few simple steps that can be taken to encourage larger growth.

One of the most important things is to start with high-quality bulbs. They should be plump and firm, with no sign of mold or damage.

Planting the bulbs in well-amended soil is also crucial for healthy growth. Once they are in the ground, onions need consistent moisture levels to perform their best.

Watering regularly during dry spells will help to keep the soil moist without saturation. Finally, fertilizing with a high-nitrogen fertilizer can give onions the extra boost they need to grow large and healthy.

By following these simple tips, you can enjoy abundant harvests of delicious, homegrown onions.

Is Epsom salt good for onion plants?

Onions are a popular crop among gardeners, but they can be tricky to grow. One important factor in successful onion cultivation is ensuring that the soil has adequate levels of sulfur.

Sulfur is essential for onion growth, but it can be difficult to keep levels high enough. This is where Epsom salt comes in.

Epsom salt is a rich source of sulfur, and applying it to the soil can help to boost levels. In addition to increasing sulfur levels, Epsom salt can also help to improve plant health.

Healthy plants are less susceptible to damage from insects and disease, making them more likely to produce a bountiful harvest.

For these reasons, Epsom salt can be a valuable tool for those looking to grow healthy onions.

How long do onions take to grow from onions?

Onions are a fast-growing crop, and it is possible to grow them from cuttings in just a few months. To get started, simply cut the bottom off an onion and plant it in the soil.

With regular watering, the onion will start to sprout new roots and shoots. In just 90 to 120 days, you can harvest your very own onion crop.

While it takes some effort to get started, growing onions from cuttings is a great way to enjoy fresh onions all year round.

Do onions like sun or shade?

Onions are a versatile vegetable that can be grown in a variety of conditions. While they prefer full sun, they can also tolerate partial shade.

However, onions grown in shady conditions will likely be smaller and have fewer cloves than those grown in full sun.

So, if you’re looking to produce large, healthy onions, it’s best to plant them in an area that receives plenty of sunlight.

However, if you’re tight on space or your garden doesn’t get much sun, onions can still be a viable option.

Just be aware that they may not reach their full potential.

What is the best fertilizer for onions?

Onions are a staple in many dishes, and their strong flavor can add a lot of depth to a recipe. However, onions can be difficult to grow, and they require a significant amount of nitrogen.

Ammonium sulfate or ammonium nitrate is the best fertilizer for onions, and it should be applied at a rate of one cup per 20 inches of row.

The initial application should occur three weeks after planting, and then the fertilizer should be reapplied every two to three weeks. With proper care, onions can be a delicious and nutritious addition to any meal.


What organic fertilizer is good for onions?

Bone meal is a slow-release fertilizer that is good for onions. Its phosphorus helps form strong roots and its calcium helps prevent blossom end rot, a common problem in onions.

Bone meal also provides other nutrients that onions need, such as potassium and magnesium. You can apply bone meal to your onion bed before planting, or top dress it around existing plants.

Be sure to water it in well after application. For best results, apply bone meal every two to three months during the growing season. You can find bone meal at most garden centers or online.

What is best feed for onions?

Onions are a staple in many dishes and can be used in a variety of ways, making them a popular choice for both home and professional cooks.

While they are relatively easy to grow, onions do have some specific requirements when it comes to fertilization and care. In general, onions require a large quantity of nitrogen in order to thrive.

As a result, the best fertilizer for onions is one that is high in nitrogen content. Ammonium nitrate or ammonium sulfate are both good choices. These fertilizers should be applied at a rate of one cup per 20 yards of row.

Additionally, onions need to be well-watered, especially during the bulb-forming stage. They also benefit from being grown in an area that receives full sun.

With proper care, onions can be a delicious and versatile addition to any kitchen.

Is tomato fertilizer good for onions?

Tomato fertilizer is often recommended for onion plants, as the nutrients in tomato fertilizer can help onions to grow and thrive.

The main nutrients in tomato fertilizer are nitrogen, phosphorus, and potassium, all of which are essential for healthy onion growth.

Nitrogen helps the plant to grow, phosphorus aids in root development, and potassium strengthens the roots. In addition, tomato fertilizer also contains trace amounts of other important nutrients, such as calcium and magnesium.

These nutrients help to promote strong cell walls and prevent disease.

Overall, tomato fertilizer is an excellent choice for those looking to provide their onion plants with the nutrients they need to grow healthy and strong.

Jessica Miles

Jessica Miles is a writer for Botanique Boutique, a plant and gardening blog. She has always loved plants, flowers, and anything green. When she was younger, she used to watch her grandfather garden and would be in awe of the beautiful flowers he would grow. Now Jessica writes about all things related to plants and gardening - from beginner tips on how to start growing your own plants, to in-depth guides on caring for a specific type of flower or plant. She loves helping others learn about this fascinating hobby, and hopes that her writing will inspire people to get outside and enjoy nature!

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