How to Grow Big, Flavorful Onions from Planting to Harvest

No Comments

This post may contain affiliate links. Please read our disclosure policy.

If you’d like to learn how to grow big, flavorful onions from planting to harvest, this post is for you! From choosing the right varieties and planting techniques to caring for your crop and harvesting at just the right time, we’ve got you covered with all the tips and tricks you need to succeed. So roll up your sleeves, grab your trowel, and let’s go garden!

How to Grow Onions

Onions are a versatile and delicious addition to any garden, and with a little know-how, you can grow healthy, flavorful bulbs that will last throughout the winter.

Many gardeners struggle with growing onions in their vegetable garden, often experiencing small or poorly formed bulbs.To learn how to grow onions successfully, start by choosing the right variety for your region and plant them at the right time. Prepare your soil with plenty of organic matter and fertilize regularly to promote healthy growth. Water deeply and consistently, and be sure to weed around your onion plants regularly. With a little patience and care, you’ll be harvesting plump, flavorful onions in no time.

By following these simple steps, you can turn your onion-growing woes into a bountiful harvest that you can enjoy for months to come. So don’t give up on growing onions in your garden – with a little care and attention, you can cultivate a delicious and healthy crop that you’ll be proud to share with your family and friends.

What to Know About Onions

If you’re only used to the onions you see in the grocery store, you might not know about the beauty of onions. They come in all colors and sizes and bring so much flavor to food at an affordable price. Onions can be sweet, spicy, big and small. Their diversity is really staggering!

It’s time to learn how to grow onions – this early spring garden plant is one of the first to plant in the vegetable garden after a long winter. Depending on the type of onion you grow, most onions go out before your last frost date during cool weather. Onions are a cool-season crop and can tolerate frost. They should be planted in soil that has warmed to at least 50°F (10°C).

Growing your own offers you a variety of spicy red onions or sweet white ones. No matter what you grow, you can enjoy an onion crop that gives bigger onions the whole season. 

How to Grow Onions

Similar to knowing how to grow big strawberries, if you want to grow big onions, you need to know the right type of onions to grow based on your location and desired outcomes.

  • Do you want to grow large onions for long-term storage, so you can eat onions all winter?
  • Do you want to grow your own onions to use up quickly, primarily in canning recipes?
  • Or do you want to grow fresh onions for eating soon after you harvest them?

The answers to these questions will help you get the best results and grow lots of delicious onions.

There are three main types of onions: Long Day, Neutral, and Short Day. Your garden’s location will determine the type of onion you should grow.

Long Day Onions

Long day onions require 14-16 hours of daylight to form bulbs. They are best suited for colder climates in northern latitudes and should be planted in early spring, as soon as the soil can be worked. In most areas, this is typically in April or May. They do well in growing zones six and below. 

Long-day onions are a good option for my zone 5b, and I like growing them because also tend to be the best long-term storage onions. They’ll store well for six or more months when kept in a cool basement or root cellar.

If you don’t know your growing zone, make sure to check it at Dave’s Garden.

Popular varieties of long-day onions include:

  1. Yellow Spanish: This is a classic long-day onion with a sweet and mild flavor. It produces large bulbs that can be stored for several months.
  2. Walla Walla: This onion is known for its large size and sweet, juicy flavor. It’s an excellent choice for eating raw in salads and sandwiches.
  3. White Sweet Spanish: This is a type of long-day onion that is known for its mild, sweet flavor and large size. It has a white, papery skin and a flattened globe-shaped bulb that can weigh up to a pound or more. White Sweet Spanish onions are often used in salads, sandwiches, and other raw dishes, as well as in cooking.

Short-Day Onions

Short Day onions require 10-12 hours of full sun a day and are best for southern growing zones where the winters are mild and the summers are hot. Short-day onions are not good for long-term storage, like the long-day varieties. Short-day onions are typically planted in the fall and harvested in the spring. They have a mild, sweet flavor and are often used in Mexican and other cuisines.

Common types of short-day onions include:

  1. Texas 1015: This is a popular short-day onion that is named after its planting date, October 15th. It has a mild, sweet flavor and is often used in Tex-Mex cuisine.
  2. Vidalia: These sweet onions often grow in Georgia and are known for their mild, delicate flavor. It’s often used in salads, sandwiches, and other raw dishes.
  3. Red Burgundy: This is a red onion with a mild, sweet flavor. It’s often used in salads, sandwiches, and other raw dishes.

Neutral or Intermediate Day Onions

Neutral day onions, also known as intermediate day onions, are a type of onion that require approximately 12-14 hours of daylight to form bulbs. They are called “neutral day” onions because they are not as sensitive to daylight hours as long-day or short-day onions.

Neutral day onions are a good choice for gardeners who live in regions with moderate climates and can be planted in both the spring and fall. They typically have a moderate flavor, falling between the mildness of short-day onions and the pungency of long-day onions.

Common types of neutral day onions include:

  1. Candy: This is a type of intermediate day onion with a sweet and mild flavor. It has a yellow skin and is often used in salads, sandwiches, and other raw dishes.
  2. Copra: This is an intermediate day onion that has a strong flavor and is often used in cooking. It has a yellow skin and is a good choice for storage.
  3. Red Zeppelin: This is an intermediate day onion with a red skin and a mild to moderate flavor. It’s often used in grilling and roasting.

The Importance of Planting Onions Suited for Your Climate

If you choose the wrong type of onion for your climate, it may not form bulbs or grow to its full potential. Day length is important when it comes to growing onions. Growing the wrong type of onion will result in a poor harvest of sad, small onion bulbs. Selecting the right type of onion for your region can help ensure the best possible outcome for your onion crop.

How to Grow Onions

When and How to Plant Onions in Your Garden

Now that you know the right type of onion variety to grow for your growing area, let’s talk about actually growing onions. There are three types of ways to plant onions:

  1. Start Onions from Seeds
  2. Plant Onion Transplants or Seedlings
  3. Plant Onions from Sets
How to Grow Onions

How to Start Onions from Seeds

Some benefits to starting onions from seeds include more variety of onions to grow, and cheaper cost. If you want to start onions from seed, start them 8-10 weeks indoors before your last frost date. You can also winter sow onion seeds outdoors in December. Learn how to use the winter sowing method here.

It takes seeds up to two weeks to germinate, and you should use a germination mat to speed the process up. Get all the tips for how to start seeds indoors in the post.

How to Grow Onions

Plant Onion Transplants or Seedlings

Another way to plant onions is to use onion transplants. This method works best for intermediate-day and long-day varieties, which are typically planted in the spring. You can often find onion transplants at garden centers or farmer’s markets if you don’t want to start the seeds yourself.

How to Grow Onions

Plant Onion Sets

The last way to grow onions is to plant onion sets. Onion sets are small bulbs that have been grown from seed and allowed to dry out. They are easy to plant and are often used for short-day onion varieties. Start by preparing the soil as described above, and then plant the sets about 1 inch deep, with the pointed end facing up. Space the sets about 4-6 inches apart in rows.

Start by preparing the soil, and then plant the transplants about 1-2 inches deep, with the top of the bulb just below the soil surface. Space the plants about 4-6 inches apart in rows.

Sets and seedlings are planted once the garden soil is workable, usually a month before your last frost date.  Well-drained soil is essential to prevent bulb rot.  You’ll want to plant them in a hole about an inch deep in early spring.  

Chives and scallions, young onions before they have bulbed up, can be planted closer together by mixing onion seeds with sand and scattering the seed within a marked location or along a straight line.  Chives are also nicely planted in a container or transplanted to bring indoors for winter use.

Best Soil For Onions

Onions prefer well-draining, loose soil that is rich in organic matter. Here are some soil characteristics that are important for growing healthy large onions. Onions prefer a slightly acidic soil pH between 6.0 and 7.0 and they need a steady supply of nutrients, especially nitrogen, phosphorus, and potassium.

It’s important to add organic matter such as compost to the soil to improve soil structure, drainage, and fertility. Onions require a good amount of nutrients to grow healthy foliage and bulbs, so rich soil is important.

Before planting onions, it’s a good idea to test the soil pH and nutrient levels to ensure that the soil is suitable for growing onions. If the soil is too acidic or nutrient-poor, add amendments to improve soil quality.

Remember, I also have a free garden planner download for my blog subscribers! Get instant access to my Subscriber Library by signing up for my email list.

What is the Best Organic Fertilizer for Onions

There are several organic fertilizers that can be used to provide the necessary nutrients for growing healthy onions. Here are a few options:

  1. Compost: Compost is a natural and nutrient-rich soil amendment that can be used to enrich the soil and improve soil structure. It also helps to retain moisture in the soil.
  2. Manure: Well-aged manure from cows, horses, or chickens can be used as a source of nitrogen, phosphorus, and potassium for onions. It’s important to use well-aged manure to avoid burning the plants with high nitrogen levels.
  3. Fish emulsion: Fish emulsion is a liquid organic fertilizer that is high in nitrogen, making it a good choice for promoting healthy foliage growth in onions. It’s also a good source of trace minerals.
  4. Bone meal: Bone meal is a slow-release fertilizer that is high in phosphorus, which is important for promoting root growth and bulb development in onions.
  5. Blood meal: Blood meal is another high-nitrogen fertilizer that can be used to promote healthy foliage growth in onions.

How Much Water Do Onions Need

As a general rule, onions should receive about 1 inch of water per week, either from rainfall or irrigation. However, the frequency and amount of watering may vary depending on factors like soil type, temperature, and humidity.

It’s important to water deeply (soaker hoses are best!), ensuring that the moisture reaches the root zone of the plants. In general, it’s better to water onions in the morning rather than the evening to avoid excess moisture on the leaves overnight, which can increase the risk of fungal diseases.

Additionally, reducing watering in the weeks leading up to harvest can help promote bulb formation and prevent excess moisture from causing the onions to rot.

Read how to make garden watering more eco-friendly here!

How to Grow Onions

How Do I Get my Onions to Grow Bigger?

If you want to grow larger onions with big bulbs, first, make sure you’re growing the best type of onion for your growing zone. Plant them at the optimum time – before your last frost date. Take care of common onion problems, water correctly, and feed well. That’s all there is to it.

What are Common Onion Growing Problems

  1. Fungal Diseases: Fusarium and botrytis are common fungal diseases that can affect onions. Proper crop rotation, good air circulation, and keeping the plants dry can help prevent these diseases.
  2. Bulb Rot: This is caused by excess moisture and poor air circulation around the onions. It can be prevented by ensuring proper drainage and spacing between plants.
  3. Yellowing Leaves: This is often caused by nutrient deficiencies, particularly of nitrogen or sulfur. It can be remedied by amending the soil with organic fertilizers or supplements.
  4. Pest Infestations: Onion maggots, thrips, and leaf miner can all cause problems for onion plants. Insecticidal soaps, wood ash, diatomaceous earth, and neem oil can all be used to manage these pests.

Read more about our favorite and most effective organic pest control methods here!

How to Grow Onions

Companion Plants for Onions: What to Grow and What to Avoid

Companion planting involves planting different plant species together to help them grow better, deter pests, and improve soil health. Here are some good companion plants for onions:

  1. Carrots: Onions and carrots make great companions as they have opposite rooting patterns. Onions grow shallow roots while carrots have long roots. Planting these two together helps them avoid competing for nutrients and space. Additionally, onions can help repel carrot flies that can damage carrot crops.
  2. Beets: Beets are also a great companion plant for onions. They help improve soil health and attract beneficial insects that can help protect onion plants from pests.
  3. Chamomile: Chamomile is a great companion plant for onions as it attracts pollinators and beneficial insects, such as hoverflies and parasitic wasps, which can help control onion pests.
  4. Lettuce: Lettuce makes a good companion plant for onions as it grows quickly and provides shade for the onions, helping to keep the soil cool and moist.

There are also a few plants you should avoid planting near onions.

  1. Alliums: Onions belong to the Allium family, which includes garlic, leeks, and chives. Planting onions with other Alliums can lead to competition for nutrients and space, as well as increase the risk of disease and pests that affect these plants.
  2. Legumes: Legumes, such as beans and peas, can fix nitrogen in the soil, which is beneficial for many plants. However, they can also attract onion maggots, which can damage onion crops.

Read more about the importance of companion planting here.

How Long Do Onions Take To Grow

In general, most onions take around 100-120 days from seed to maturity. Short-day onions typically mature faster, around 90-100 days, while long-day onions can take up to 150 days to mature.

An interesting onion fact: onions are a biennial plant, meaning they require two growing seasons to complete their life cycle. However, most gardeners grow onions as an annual crop, harvesting them before they go to seed in their second year.

How to Grow Onions

When to Harvest Onions

Onions are typically ready to harvest when the tops have fallen over and begun to dry out, usually in late summer or early fall. The tops of the onions should be yellow and papery, and the bulbs should feel firm and have a well-defined shape. It’s important to avoid leaving onions in the ground too long, as over-mature onions may begin to rot or sprout.

How to Harvest Onions

How to Grow Onions

To harvest onions, gently loosen the soil around the bulbs with a garden fork and lift them out of the ground.

Do not wash your onions. Pull them up on a dry soil day, so the onion is as naturally free of soil clods as possible. Lay the onions on the bed or on a table to dry. We’ve also used a wire dog crate as a drying table! Works great!

Cover them with a blanket or tarp before the cool night air comes in on them each night. Let them dry until the leaves are no longer green. You can also hang them with twine to let them dry under cover of a porch, shed, barn or garage.  

You will want to harvest your onions at the end of summer/beginning of fall when the leaves have flopped or bent at the neck, and the leaves are beginning to or have dried.  If your leaves have flopped or bent at the neck but are still green, you can pull the onion up and lay it on a rack to dry out. 

About Michelle Marine

Michelle Marine is the author of How to Raise Chickens for Meat, a long-time green-living enthusiast, and rural Iowa mom of four. She empowers families to grow and eat seasonal, local foods; to reduce their ecological footprint; and to come together through impactful travel.

You May Also Like:

Leave a comment

Your email address will not be published. Required fields are marked *