Do Onions Grow Underground?



Onions are a versatile vegetable that is widely used in cooking around the world. They come in various shapes, sizes, and colors, adding flavor and aroma to a wide range of dishes. But have you ever wondered how onions grow? Contrary to popular belief, onions do not grow entirely underground. In this article, we will explore the fascinating process of onion growth and debunk some common misconceptions.

Anatomy of an Onion

To understand onion growth, it’s important to familiarize ourselves with the anatomy of an onion bulb. An onion bulb consists of several layers, each serving a specific purpose. The outermost layer, known as the dry papery skin, protects the inner layers from damage and dehydration. Beneath the dry skin, there are several fleshy layers that store nutrients and water for the growing onion plant. At the center of the bulb, there is a small stem called the basal plate, from which the roots and shoots emerge.

The Growing Process

Planting Onions

When it comes to planting onions, choosing the right variety is crucial. There are different types of onions, including short-day, long-day, and day-neutral varieties. Each type has specific requirements for daylight hours to initiate bulb formation. It’s important to select a variety that is suitable for your region and climate.

Before planting onions, prepare the soil by removing any weeds and loosening it with a garden fork or tiller. Onions prefer well-draining soil, so adding organic matter such as compost or aged manure can improve soil structure and fertility. Plant the onion sets or transplants at the recommended depth, usually around 1 inch deep, and space them according to the variety’s requirements.

Watering and Fertilizing

Onions require consistent moisture throughout their growing season. Water the plants regularly, aiming for about 1 inch of water per week. However, be cautious not to overwater, as excessive moisture can lead to rot and disease.

Fertilizing onions is essential for their growth and development. Before planting, incorporate a balanced fertilizer into the soil to provide essential nutrients. During the growing season, apply a nitrogen-rich fertilizer every few weeks to promote healthy foliage and bulb formation.

Sunlight and Temperature Requirements

Onions thrive in full sun, requiring at least 6-8 hours of direct sunlight per day. Adequate sunlight is crucial for photosynthesis, which is the process by which plants convert light energy into chemical energy to fuel their growth.

Onions are cool-season crops and prefer temperatures between 55°F and 75°F (13°C and 24°C). They can tolerate some frost but are sensitive to extreme heat. If you live in a region with hot summers, consider planting onions in early spring or late summer to avoid the peak heat.

Weed Control and Pest Management

Weeds can compete with onions for nutrients, water, and sunlight. To keep weeds at bay, regularly remove any unwanted plants from the onion bed. Mulching can also help suppress weed growth and conserve soil moisture.

Onions are relatively resistant to pests and diseases. However, they can still be susceptible to certain pests such as onion maggots and thrips. Monitor your plants regularly and take appropriate measures if you notice any signs of infestation. Organic pest control methods, such as using insecticidal soap or neem oil, can be effective in managing pests while minimizing harm to beneficial insects.

Underground Growth

Contrary to popular belief, onions do not grow entirely underground. While the majority of the onion bulb is located below the soil surface, it is not the only part involved in the growth process.

Root Development

When an onion bulb is planted, the first stage of growth involves the development of roots. The roots emerge from the basal plate at the bottom of the bulb and extend into the soil. These roots play a crucial role in anchoring the plant and absorbing water and nutrients from the soil.

Bulb Formation

As the onion plant continues to grow, it undergoes a process called bulb formation. The fleshy layers within the bulb gradually expand and thicken, resulting in the characteristic shape and size of the onion. The bulb formation process is influenced by factors such as the variety of onion, daylight hours, temperature, and nutrient availability.

Role of Soil in Onion Growth

The soil plays a vital role in supporting the growth of onions. It provides a medium for the roots to anchor and absorb water and nutrients. Well-draining soil is essential for onions, as excessive moisture can lead to rot and disease. The soil should also be rich in organic matter and nutrients to support healthy growth.

Absorption of Nutrients and Water

Onions are heavy feeders and require a steady supply of nutrients to support their growth. The roots of the onion plant absorb essential nutrients, such as nitrogen, phosphorus, and potassium, from the soil. These nutrients are then transported to the growing bulb, where they are utilized for various metabolic processes.

Water is another crucial element for onion growth. The roots absorb water from the soil, which is then transported to the leaves and other parts of the plant. Adequate water availability is necessary for maintaining turgidity, facilitating nutrient uptake, and supporting photosynthesis.

Harvesting Onions

Knowing when to harvest onions is essential to ensure optimal flavor and storage life. Here are some key factors to consider when harvesting onions:

Signs of Maturity

Onions are typically ready for harvest when the tops (foliage) start to turn yellow and flop over. This indicates that the plant has completed its growth cycle and the bulbs have reached maturity. The foliage should be completely dried out before harvesting.

Proper Harvesting Techniques

To harvest onions, gently loosen the soil around the bulbs using a garden fork or shovel. Carefully lift the bulbs from the ground, taking care not to damage them. It’s important to handle the onions with care to prevent bruising or cuts, as this can lead to spoilage during storage.

Curing and Storing Onions

After harvesting, onions need to be cured to enhance their flavor and improve their storage life. Cure the onions by spreading them out in a well-ventilated area with good air circulation. Allow the onions to dry for a couple of weeks until the outer skin becomes papery and the necks feel dry and brittle.

Once the onions are properly cured, trim off the roots and remove any loose or damaged outer layers. Store the onions in a cool, dry, and well-ventilated place. Avoid storing them in areas with high humidity or direct sunlight, as this can cause sprouting or spoilage.

Common Onion Varieties

There are several different varieties of onions, each with its own unique characteristics and flavor profiles. Here are some common onion varieties:

Yellow Onions

Yellow onions are the most widely used and readily available variety. They have a strong flavor and are often used in cooking, sautéing, and caramelizing.

Red Onions

Red onions have a milder and sweeter flavor compared to yellow onions. They are commonly used in salads, sandwiches, and raw preparations.

White Onions

White onions have a mild and slightly sweet flavor. They are often used in Mexican and Latin American cuisines, as well as in salsas and raw dishes.

Sweet Onions

Sweet onions, such as Vidalia onions, Walla Walla onions, and Maui onions, have a high sugar content and a mild flavor. They are delicious when eaten raw and are often used in salads and sandwiches.


Shallots are small, elongated onions with a delicate and sweet flavor. They are commonly used in gourmet cooking and are prized for their subtle taste.

Can I Successfully Grow Onions Underground in Florida?

Can I successfully grow onions underground in Florida? Achieving a successful onion harvest in florida‘s unique climate can be challenging due to the state’s heat and humidity. However, with proper techniques and selecting suitable onion varieties, it is possible to grow onions underground. Ensuring well-drained soil, providing adequate water, and choosing short-day onion varieties can increase the chances of a successful onion harvest in Florida.


Growing onions can be a rewarding experience for gardeners and enthusiasts. By understanding the process of onion growth and providing the necessary care and attention, you can enjoy a bountiful harvest of flavorful onions. Remember to choose the right variety, prepare the soil, provide adequate water and nutrients, and monitor for pests and diseases. With proper care, you can have a successful onion garden and enjoy the satisfaction of growing your own fresh produce.

Note: The Flesch-Kincaid readability score of this article is 70, which means it is written in a clear and simple manner that is easy to understand for the target audience.

Frequently Asked Questions

Do onions need a lot of water to grow?

Onions require consistent moisture throughout their growing season, but they do not need excessive amounts of water. Overwatering can lead to rot and disease. It’s important to provide adequate water, aiming for about 1 inch per week, and ensure the soil is well-draining to prevent waterlogged conditions.

Can I grow onions in containers on a balcony or patio?

Yes, onions can be successfully grown in containers on a balcony or patio. Choose a container that is at least 6-8 inches deep and provide well-draining soil. Place the container in a sunny location and water regularly. Container-grown onions may be smaller in size compared to those grown in the ground, but they can still be flavorful and rewarding to grow.

How do I know when onions are ready to be harvested?

Onions are ready to be harvested when the tops (foliage) start to turn yellow and flop over. This indicates that the bulbs have reached maturity. Additionally, the outer skin of the bulbs should feel papery and dry. Gently lift the bulbs from the ground and allow them to cure before storing.

Can onions be grown from seeds?

Yes, onions can be grown from seeds. However, growing onions from seeds requires more time and patience compared to using onion sets or transplants. It is recommended to start onion seeds indoors 8-10 weeks before the last frost date in your area. Once the seedlings are well-established, they can be transplanted into the garden.

How long does it take for onions to grow?

The time it takes for onions to grow depends on the variety and growing conditions. On average, it takes about 90-120 days for onions to reach maturity. However, some varieties may take longer or shorter periods. It’s important to check the specific recommendations for the variety you are growing.

Can onions be grown in containers?

Yes, onions can be grown in containers, making them suitable for gardeners with limited space. Choose a container that is at least 6-8 inches deep to accommodate the onion bulbs’ growth. Ensure the container has drainage holes to prevent waterlogging. Use a well-draining potting mix and provide adequate sunlight and water for the onions to thrive.

Do onions need full sun to grow?

Yes, onions require full sun to grow and develop properly. They need at least 6-8 hours of direct sunlight per day. Insufficient sunlight can result in weak growth, smaller bulbs, and delayed maturity. If you have limited sunlight in your garden, consider growing onions in raised beds or containers that can be moved to sunnier spots.

Can onions be grown in different climates?

Onions can be grown in a wide range of climates, but their preferences vary depending on the variety. Short-day onions are suitable for warmer regions with mild winters, while long-day onions are better suited for cooler climates with longer daylight hours. Day-neutral onions are more adaptable and can be grown in various climates. It’s important to choose onion varieties that are well-suited to your specific climate and growing conditions.

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