How to grow onions: Tips for fresh bulbs and greens

Vegetables grown at home are fresher, free from harmful chemicals, and often taste better than the ones bought from the store. Moreover, for many people gardening is a relaxing activity that provides fresh, healthy food for the whole family. Among all the vegetables, onions are one of the most versatile to grow. They add flavor, texture, and nutrition to a wide variety of dishes, from soups to salads. 

Growing onions at home has many advantages. Freshly harvested onions have an unbeatable flavor. It is also budget-friendly since a small investment in seeds or sets can provide a steady supply of onions for months. These vegetables grow well in different spaces, making them an excellent choice for any home gardener.

Growcycle supplies high-quality soil mixes and customized fertilizers to boost onion yield and improve quality. This article highlights how to plant, care for, and harvest flavorful onion bulbs and greens.

Botanical Description

Onions are a biennial plant commonly grown as an annual for their bulbs. They belong to the Amaryllidaceae family and the Allium genus. Below is a detailed description of their botanical features:

1. Roots

• Onions develop a shallow, fibrous root system.
• The roots grow from the base of the bulb (called the basal plate) and are not very deep. They typically extend 6-12 inches into the soil.

2. Bulbs

• The bulb is the most notable part of the onion plant, formed by concentric layers of fleshy, modified leaves.
• The outer layers are dry and papery, protecting the inner fleshy scales, which store water and nutrients.
• The size, shape, and color of the bulb vary depending on the variety.

3. Leaves

• Onion leaves are hollow, tubular, and grow upright from the base of the plant.
• The leaves are green, waxy, and photosynthetic, contributing to bulb development.
• The number of leaves often correlates with the size of the bulb, as each leaf represents a scale in the bulb.

4. Flowers

• Onions produce flowers in their second year of growth if left unharvested.
• The small, white flowers form round, umbel-shaped clusters at the tip of a tall, hollow stalk.
• The stalk can grow up to 3 feet tall, depending on the variety.
• The flowers are hermaphroditic, containing both male and female reproductive parts, and are pollinated by insects.

5. Seeds

• Onion seeds are small, black, and angular.
• They are produced after the flowers are pollinated and are commonly used for propagation.

6. Growth Habit

• Onions grow in a rosette pattern during their vegetative phase.
• The plant produces bulbs during its reproductive phase, typically triggered by day length and temperature.

7. Lifespan and Growth Cycle

• Biennial Nature: In the first year, onions grow leaves and bulbs. In the second year, they flower and produce seeds.
• Day-Length Sensitivity: Onions are classified into short-day, intermediate-day, and long-day varieties based on the photoperiod required to form bulbs.

Onion Varieties

Onions come in various types, each with its own flavor profile, color, shape, and suitability for different climates and uses. Here is an overview of the main onion varieties:

1. Bulbing Onions

These are the most common types of onions grown for their large, edible bulbs. They are divided into three categories based on their color:

Yellow Onions

• The most widely used onion variety.
• They are known for their rich, sweet flavor that deepens when cooked.
• Excellent for soups, stews, and sautéing.
• Great for long-term storage.
• Examples: Yellow Globe, Yellow Granex.

Red Onions

• Have a mild, sharp flavor with a slight sweetness.
• Ideal for raw applications, such as in salads, salsas, and sandwiches.
• Their vibrant purple-red skin and flesh make them an attractive addition to any dish.
• Examples: Red Burgundy, Red Wethersfield.

White Onions

• Milder in taste compared to yellow onions, with a crisp texture.
• Commonly used in Mexican cuisine, salads, or as a garnish.
• Tend to have thinner skin and a more delicate flavor than yellow onions.
• Examples: White Pearl, White Lisbon.

2. Green Onions (Scallions)

• Green onions are harvested for their tender green tops and small, mild white bulbs.
• They grow quickly and are typically ready for harvest in a few weeks.
• Known for their mild flavor, they are often used raw in salads, garnishes, or stir-fries.
• Examples: EverGreen, White Lisbon.

3. Shallots

• Shallots are smaller than regular onions, with a mild, sweet flavor that is less pungent.
• The outer skin is usually reddish-brown or grayish, while the inner flesh is white or purple-tinged.
• They are commonly used in French and Mediterranean cooking for sauces, dressings, or as a garnish.
• Examples: French Shallots, Yellow Shallots.

Benefits of Home Grown Onions

Growing onions at home brings many advantages that can improve both the garden and the kitchen. Here are the main benefits:

1. Freshness and Better Flavor

Onions grown at home taste fresher and more flavorful than store-bought onions, which may have been stored for a long time. Home gardeners can pick their onions when they are perfectly ripe, ensuring the best taste.

2. Save Money

Growing onions at home reduces the need to buy them, saving money over time. One planting can produce a large supply of onions, making them a cost-effective crop.

3. Healthier Choice

Home grown onions are free from pesticides and chemicals often used in commercial farming, making them healthier. They are full of vitamins, antioxidants, and compounds that can help boost immunity, support heart health, and reduce inflammation.

4. Better for the Environment

Growing onions at home reduces the need for transportation, cutting down on carbon emissions. They usually don’t need plastic bags or packaging, reducing waste.

5. Easy Access

With home grown onions, there is no need to go to the store. Fresh onions are ready to be picked whenever needed. Green onions (scallions) can be harvested multiple times, giving a steady supply throughout the season.

6. Suitable for Small Spaces

Onions can be grown in small spaces like containers or raised beds, making them ideal for people with limited garden space. They are adaptable and can grow in various climates and spaces, whether in a sunny backyard or on a balcony.

7. Health Benefits

Onions have been used in traditional medicine for their potential healing properties, including being a natural remedy for colds, coughs, and other respiratory issues. They contain compounds that are believed to boost immune function, making them a good choice for natural health improvement.

How to Grow Onions in Home Garden

With proper planning and care, people can enjoy fresh, home grown onions for all their cooking needs. Here is a simple guide to help gardeners grow onions successfully at home:

1. Selecting the Location

To grow well, onions need at least 6-8 hours of sunlight each day. Choose a spot in the garden with plenty of light to help them grow strong and healthy. They prefer well-draining, fertile soil with a neutral pH (around 6.0 to 7.0). The soil should not hold water too long, which can cause the onions to rot.

2. Choose the Planting Method

Seeds: Growing onions from seeds is cost-effective but takes more time. It’s best for gardeners who have a longer growing season.

• Pros: Wide variety of onions, inexpensive.
• Cons: Takes longer to grow and requires early indoor planting or direct sowing.

Sets (Small Bulbs): These are immature onions that are already partially grown. They are easy to plant and produce faster results.

• Pros: Quick to grow, less care needed.
• Cons: Fewer varieties are available, so it is not ideal for long-term storage.

Transplants are young onion plants that have already been started from seed and are ready to be planted in the ground.

• Pros: Fast-growing, easier to handle than seeds.
• Cons: It can be more expensive than sets or seeds.

3. Preparing the Soil

Before planting, check the pH of the soil. Gardeners can use a soil pH test kit, which is available at garden centers. If the soil is too acidic, add lime; if too alkaline, add sulfur. Enrich the soil by adding compost or organic matter. This will provide essential nutrients and improve soil structure, which helps onions grow better.

Good drainage is crucial for onions. If the soil is heavy or clay-like, growers may need to add sand or organic material to improve drainage and prevent water from pooling around the onions, which could cause rot.

4. When to Plant Onions: Spring vs. Fall

Depending on the climate, onions can be planted in spring or fall. In most areas, spring is the best time to plant them. However, in mild climates, fall planting is also possible.

Onions need cool weather for the first few months of growth and warmer weather as they mature. Plant onions in early spring, about 4-6 weeks before the last expected frost. For fall planting, choose varieties that can grow before the first frost.

5. How to Plant Onions

Space onion sets or transplants 4-6 inches apart in rows. If growing from seeds, space them a little further apart to allow room for growth.

• For sets and transplants: Plant them about 1-2 inches deep, ensuring the top of the bulb or plant is just below the soil surface.
• For seeds: Plant them about ¼ inch deep. Ensure proper spacing to give each plant room to grow.

Onions can also be grown in containers. Choose a deep container (at least 10-12 inches deep) to allow the bulbs to grow. Ensure it has drainage holes and use a good-quality potting mix.

6. Companion Planting Tips

Onions can benefit from being planted alongside certain vegetables. Here are some tips for companion planting with onions:

• Carrots: Onions and carrots grow well together. Their roots do not compete; onions can help repel pests like carrot flies.
• Lettuce: Onions can help keep pests away from lettuce, and the two plants don’t compete for nutrients, making them good companions.
• Beets: Beets and onions have complementary growth habits and grow well together in the same space.

Caring for Onion Plants

Taking care of onion plants properly is important to help them grow strong and produce good bulbs. Here is how to take care of onions:

1. Watering

Onions need regular watering. They should be watered deeply every 2-3 days, especially in dry weather. The soil should stay moist but not soaked. Water the onions at the base, not on the leaves, to keep them dry. A soaker hose or drip irrigation is the best way to water onions without getting the leaves wet.

Overwatering can cause onion rot. It’s important that the soil drains well and doesn’t stay too wet, which can lead to disease.

2. Fertilizing

Onions grow best when fed with organic fertilizers or compost. These provide the right nutrients without harming the plants. Add fertilizer or compost when people plant the onions to give them a good start. Once the onions start growing, feed them again with a fertilizer that has more nitrogen to help the leaves grow strong.

When the onions start forming bulbs, switch to a fertilizer high in nitrogen, like ammonium sulfate or urea, to help the bulbs grow large. Don’t overfeed the onions, which can lead to too much leaf growth and smaller bulbs.

3. Weeding and Mulching

Weeds can remove nutrients and water from onions, so removing them regularly is important. Pull weeds carefully so you don’t disturb the onion roots.

Mulch helps keep the soil moist, prevents weeds, and keeps the temperature stable. After the onions grow a few inches tall, spread mulch like straw around the plants. This will also protect the bulbs from the sun.

4. Dealing with Pests and Diseases

• Onion Maggots: These pests lay eggs near onions, and the larvae burrow into the bulbs. To prevent this, use row covers or rotate onion crops each year.
• Thrips: Tiny insects that damage the onion leaves. Use insecticidal soap or neem oil to control them.
• Onion Rot: This fungus causes the bulbs to rot. To prevent it, don’t overwater, make sure the soil drains well, and rotate crops.
• Downy Mildew: This disease causes yellow spots on onion leaves. Remove infected leaves and use a fungicide if necessary.

Harvesting Onions

Onions take about 3-4 months to grow from sets or transplants, but they can take up to 6 months if grown from seeds.

Harvesting Bulbs

Onions are ready to harvest when their leaves turn yellow and start to fall over. Depending on when they were planted, this usually happens in late summer or early fall.

Gently pull the onions out of the ground. If the soil is heavy, use a garden fork to lift them carefully without damaging the bulbs.

After harvesting, onions need to be cured. Place them in a warm, dry, and well-ventilated area for 2-3 weeks. This helps them dry out completely, making them last longer in storage.

Harvesting Greens

Green onions (scallions) can be harvested when they are about 6-8 inches tall. The tops can be cut as needed for fresh use, leaving the roots in the soil so they can continue growing.

If growers want the plant to keep growing, use scissors or a sharp knife to cut the green tops above the white bulb, leaving the roots intact 

Store cut green onions in the refrigerator on a damp paper towel or place them in a glass of water to keep them fresh for longer.

Storing and Using Onions

After harvesting onions, it is important to store them the right way to keep them fresh and make them last longer.

Storing Cured Onions

Once the onions are cured, store them in a cool, dry, and dark place, such as a pantry, basement, or garage. The ideal temperature is between 32°F and 40°F (0°C to 4°C), with low humidity. Make sure the storage area has good airflow to prevent mold or rot from forming.

Store onions in mesh bags, wire baskets, or even old pantyhose. These options allow air to flow around the onions and help keep them dry. Avoid using plastic bags, as they trap moisture and can cause the onions to rot.

If stored properly, cured onions can last for 3 to 6 months, depending on the type of onion and storage conditions.

Storing Green Onions

Store leftover green onions in the fridge. To keep them fresh, wrap them in a damp paper towel or place them in a container with a lid. Another way to keep them fresh is to place the roots in a glass of water. Change the water every few days, and the onions will keep growing for future use.

FAQs

How long does it take to grow an onion?

Onions take about 3-4 months to grow from sets or transplants, but they can take up to 6 months if grown from seeds.

What is the best fertilizer for onions?

The best fertilizer for onions is one high in nitrogen, like ammonium sulfate or urea, to promote healthy growth.

Do onions grow after cutting?

After being cut, onions, especially green onions, can grow new green tops. Place the root end in water, and it will continue to grow. However, the bulb will not regrow once it’s harvested.

The Bottom Line

Growing onions at home provides fresh, tasty food that is free from chemicals. Home grown onions can be used in many dishes, adding flavor and nutrition. By following easy steps like choosing the right place to plant, taking care while planting, and using proper methods for harvesting and storing, anyone can grow their own onions. With the right care and use of fertilizers from Growcycle, gardeners can get the maximum onion yield.

Disclaimer: This material is for informational purposes only and should not be relied on for legal, medical, financial, or any other form of professional advice.

About the Author

Victor Miller

Environmental Journalist Focused on Sustainable Agriculture

Victor Miller is an environmental journalist at Growcycle, specializing in sustainable agriculture. With a passion for storytelling, he highlights the latest trends, innovations, and practices that promote ecological balance and responsible farming.