Do Onions Grow Underground? (Explained)

Kasey Spencer
Do Onions Grow Underground

Today, we are peeling back the layers on a kitchen staple – the humble onion. Onions, a key ingredient in cuisines around the world, not only bring tears to our eyes but also add flavor and health benefits to our diets.

But have you ever stopped to ponder where onions come from? Not from the grocery store aisle, of course, but how do they grow? More specifically, do onions grow underground? It’s a simple question, yet many aren’t aware of the answer. In this blog post, we’re going to unearth the truth about how onions grow.

My years of gardening experience have granted me an intimate understanding of this interesting process. Let’s dig in!

Do Onions Grow Underground?

Onions do grow underground! This might come as a surprise to some, considering that when we typically picture plants, we envision green leaves and tall stems extending toward the sky. However, the real magic with onions happens beneath the soil, out of sight.

An onion plant begins its life as a small seed. Once planted, the seed germinates and sends out tiny roots that anchor it to the soil. As the plant grows, green shoots emerge and break through the soil surface.

These shoots, also known as scallions, are the above-ground part of the onion and help to carry out photosynthesis, a process that provides the plant with the energy it needs to grow.

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While these green shoots are essential, the main event takes place underground, where the onion bulb develops. This bulb formation process starts when the onion plant is about 12 weeks old. As the plant absorbs sunlight through its leaves, it produces and sends energy down to the bulb. This energy is stored in the form of carbohydrates, causing the bulb to expand and grow.

In essence, the part of the onion we consume is a swollen underground stem of the plant. It’s a storage organ, filled with the nutrients the plant will need to survive and regrow in the next growing season. We harvest and consume this nutrient-dense bulb, delivering those nutrients, flavors, and health benefits to our plates.

The life cycle of an onion is a remarkable testament to nature’s ingenuity. Each stage of growth, from the seed to the bulb, plays a crucial role in creating the delicious and versatile vegetable we know and love.

green onion planted at home
green onion planted at home

Understanding Onion Anatomy

To appreciate how onions grow, it’s essential to understand their anatomy. An onion plant is a fascinating specimen with two main components: the part that grows above the ground, which includes the leaves and flower stalks, and the part that grows underground, namely the bulb and roots.

1. Bulb and Roots: The Underground Parts

The bulb of an onion, the part we’re most familiar with, is an underground stem of the plant. It primarily serves as a storage organ. The bulb stores energy and nutrients, ensuring the survival of the plant through seasons when growth conditions aren’t ideal, like winter.

If you’ve ever cut an onion, you’ve noticed that it consists of concentric layers.

These layers are essentially modified leaves that the plant uses to store energy. You’ll find the basal plate at the bottom of the bulb, from which roots grow. These roots anchor the plant in the ground and absorb water and nutrients from the soil.

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2. Leaves and Flower Stalks: The Aboveground Parts

Emerging from the bulb are green, tubular structures known as leaves or scallions. These leaves are vital for photosynthesis, the process by which plants convert sunlight into energy. The energy generated through photosynthesis is transported down to the bulb, where it is stored for later use.

As the onion plant matures, it sends up a central stalk, eventually forming a round cluster of flowers at its tip. This flower cluster is known as an umbel. Once pollinated, these flowers produce seeds, ensuring the continuation of the plant’s lifecycle.

The simple yet complex structure of the onion plant reflects its adaptation to thrive and survive. Every part has a crucial role to play, from photosynthesis in the leaves to energy storage in the bulb, all working in harmony to create a vegetable that is as flavorful as it is beneficial to our health.

How Do Onions Develop Underground?

The development of an onion underground is a marvel of nature, a complex process fine-tuned over millions of years of evolution. It involves several stages, each crucial to the growth of the onion we eventually harvest and consume.

The onion’s journey begins when a small, black seed is sown into the soil. After the seed is planted and watered, it germinates, sending out slender white roots that anchor it to the ground. These roots begin absorbing nutrients and water from the soil, providing the young plant with the nourishment it needs to grow.

Above the soil, the seedling sprouts green shoots known as leaves or scallions. These leaves carry out photosynthesis, the process that converts sunlight into energy. While the roots are absorbing nutrients from the soil, the leaves are hard at work absorbing sunlight.

The energy created during photosynthesis is sent back down into the bulb. There, it’s converted into starches and stored within the layers of the onion bulb, causing it to swell and grow. This growth is the result of cell division and enlargement, which is fuelled by the energy and nutrients being sent down from the leaves and roots.

The type of soil in which an onion grows can significantly influence its development. Light, well-draining soils are ideal for onion growth because they allow the bulb to expand freely. Heavier clay soils can restrict bulb expansion, leading to smaller onions.

Sunlight also plays a critical role in onion development. As a general rule, onions need at least 6 hours of direct sunlight each day. The amount of sunlight the plant receives directly affects the bulb’s size, as more sunlight means more energy for growth.

The process of onion development is a testament to the intricate balance of nature. It showcases how different elements—sunlight, soil, water, and the onion’s anatomy—work together in harmony to create a nutrient-packed bulb beneath the earth’s surface.

Common Misconceptions About Growing Onions

There are many misconceptions surrounding the cultivation of onions, and understanding these can help you better appreciate the complexity of this vegetable’s growth. Here, we’ll debunk some of the most common myths.

Common Misconceptions About Growing Onions
Image: Kasyap // Wikimedia Commons

Misconception 1: Onions Are Root Vegetables

One of the most common misconceptions is that onions are root vegetables, like carrots or radishes. In reality, onions are not roots but bulbs, which are modified stems. The onion bulb grows underground, but it’s an energy storage unit for the plant, not a root that absorbs water and nutrients.

Misconception 2: The Size of The Onion Bulb Depends on Plant Size Above Ground

Some people believe that the larger the above-ground part of the onion plant, the larger the bulb. This isn’t necessarily true. The size of the onion bulb depends more on the variety of onion, the conditions in which it’s grown, and the care it’s given during its growing season. More leaves do mean more photosynthesis, which can contribute to bulb size, but it’s not the sole factor.

Misconception 3: Onion Plants Need Lots of Water

While onions, like all plants, do need water to grow, they require less water than many other plants. Overwatering can lead to bulb rot and other diseases. It’s essential to provide consistent and moderate watering, allowing the soil to dry out slightly between waterings.

Misconception 4: All Onions Taste The Same

Onions come in a variety of types, each with its distinct flavor. Factors like the onion’s variety, the soil it’s grown in, and its maturity at harvest can significantly affect its taste. Not all onions are created equal in the flavor department!

Understanding these misconceptions can help you better appreciate the process of growing onions, as well as the care and knowledge it takes to cultivate this versatile vegetable. Gardening is a blend of science and art, and onions are a perfect example of this delicate balance.

Wrapping it up

In conclusion, onions are truly remarkable plants. They start from a tiny seed and, with the right blend of sunlight, soil, and care, they develop into a flavorful bulb beneath the ground.

These underground wonders are more than just a kitchen staple; they represent a fascinating journey of growth and development. Remember, the next time you slice into an onion, you’re not just cutting into a vegetable, but a marvel of nature’s ingenuity.

This exploration of the onion’s life cycle, we hope, has deepened your appreciation for these humble bulbs. Gardening and understanding how our food grows is a continuous learning process, filled with moments of awe and wonder.

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