onion growing stages infographic

Understanding the onion growing stages can seem intimidating since onions are bulbs, unlike many other vegetables. However, the onion life cycle is easy to understand after just a little examination.

Read on as our plant experts give you all the details necessary to figure out all stages of an onion’s growth.

What Are the Stages of Onion Growth? 

The stages of onion growth are germination, seedling, bulb development and maturation. Each stage is detailed below for the gardener who plans to harvest their onion before they have the opportunity to bolt and create a flower and seeds. 

– Germination

Like all other seeds, the onion seed first germinates before it can grow. During germination, the moisture and heat makes the outer layer of the seed peel away so that the embryo develops.  Depending on soil type, moisture and the seed variety, germination takes anywhere from a week to over two weeks. 

– Seedling 

Once the baby onion has a few adult leaves, it is called a seedling. At this point, the baby onion is beginning to develop a root system too. Onions require soil with good drainage since their root systems are shallow. If you have clay soil, it is recommended to supplement with sand to stop clumping. 

You should also know that the seedling grows more roots and a few more adult leaves until it is ready to start intense vegetative growth. 

– Vegetative Growth

In the vegetative growth phase, the onion grows leaves rapidly. Your onion will go from a few small leaves to eight to ten flourishing ones. The onion stops growing leaves when it is ready to grow the bulb.   

– Maturation

Maturation is also called ‘bulb initiation.’ That’s when the onion uses its well-developed leaves to put all its energy into growing the bulb.

Maturation Stage for Onions

After a few weeks, you can actually see the top of the onion because the bulb pops out of the ground! The leaves will also fall over and lay on the ground. 

– Harvest

At this point, the onion will not grow any further and it is wise to harvest it. Once you harvest all of your onions, you can dry them and store them for use or sale. 

And with that, these are the four major onion stages of growth! 

What Is The Onion Life Cycle Like and When Should You Harvest?

The onion life cycle occurs over two years like many other root vegetables. Having a two year life cycle allows the plant to put all of its energy into growing green leaves and creating a reserve of energy stores for the following year. This ‘reserve’ is known as the bulb. It’s also one part of the onion that we eat.  

Normally, farmers harvest onion bulbs at the end of the first year. They do this because the bulb is at its biggest point. If the onion was allowed to grow naturally, it would resprout in the spring and grow a flower. All of its stored energy would go into growing the flower, reducing the size of, and shriveling up, the bulb. 

When a plant on a two-year cycle develops a flower and uses up the energy stored in its root, it is called ‘bolting’ or ‘going to seed.’ Unless your goal is to farm the plant specifically for seeds, this renders the onion useless and is the opposite of the goal. So, make sure to harvest your onions before they go to seed!

What Are The Planting, Harvesting and Growing Specifics of Different Onion Types?

Here is a table with all the planting, harvesting and growing specifics of each onion type to help you out:

Onion  Also Known As Plant in  Harvest  Grown 
Green Scallions  Early spring  Early, while immature In bunches 
White Common Early spring  Fall Alone 
Yellow Common Early spring  Fall Alone
Purple Common  Early spring  Fall Alone


Just a baby common onion Early spring  End of spring or early summer Alone or in bunches


– What Are Onion Seeds? 

Onion seeds are the vessels by which onions reproduce and propagate themselves. Farmers obtain onion seeds by allowing a field of onions to grow for two years and bolt.

Onion Seeds to Plant

However, the onion seeds can’t be sown directly like beans or peas. Grow onion seedlings in a greenhouse container for six to eight weeks prior to planting them in the ground. 

However, using onion seeds requires a lot of foresight. We recommend putting the onions into the soil only when temperatures are regularly above 28 F. That’s because onion plants enjoy the cold weather and will thrive in the chilly air and cold soil.

Since onions are cold-weather crops, you can plant them in early spring or late fall, if you live in a mild area. Just remember to customize the variety to how long your growing season is and how much sun you have.


– What Are Onion Sets? 

Onion sets are tiny onion bulbs that are from the previous year. Growers harvested these onions before they were ready and kept them in cold storage until the following year. Growing sets is easier than growing onions directly from seed. It takes less time to get an onion. 

However, they are most likely to bolt because it’s the second year they’re alive. 

– What Are Onion Transplants? 

Onion transplants are fresh juvenile onions that are commercially grown from seed and then sold. You can buy a box of transplants online or at specialty gardening stores. These bulbs are fresh, not sets from the prior year, so they are less likely to bolt. Transplants skip the long germination and part of the seedling stage of growth. 

Plant transplants are created as soon as the temperature of the soil is consistently above 28 F. They grow the largest bulbs and have the lowest chance of bolting. They’re the least amount of work out of all three options, so they’re great for beginners. 

– What is the Difference Between Spring Onions and Green Onions? 

The difference between them is that spring onions and green onions are two different kinds of bulb vegetables. Green onions are also known as scallions, while spring onions are just common onions harvested early in the season. What makes these two onion varieties different, and how can you accommodate that in your garden? Read on to find out. 

– Spring Onions

Spring onions aren’t a different species of onion. They are common onions that are harvested early – in the spring or summer – before they are ripe.

Harvesting Spring Onions in Summer

The spring onion growing stages are similar to the common onion’s, except for harvesting. Harvest spring onions when the bulb is about one inch in diameter and the leaves are still green and tender.

– Green Onions 

Green onions are scallions, not immature common onions. Farmers grow them in bunches that are harvested early. They have no bulb, just a white stalk that is as thick as the green part of the plant. 

Green onions are harvested for the hollow, tubelike onion tops that are cut off and used as garnishes on dishes. The bulb is barely noticeable at the base of the plant and it can’t really be called a ‘bulb’ as it makes very little to no bulge.

The small white part of the onion has a more delicate flavor and can be discarded, chopped and incorporated into the dish, or used as a garnish. Furthermore, green onion growing stages are just like those for regular onions, except for two major differences. 

First, green onions are sold whole. Second, they are harvested prior to the full formation of the bulb. If you purchase a green onion in the store, don’t forget to wash the onion and the greenery prior to serving!

– What Colors of Common Onions Are There?

Common onions come in a range of colors: purple, white and yellow. With transplants, the color of the onions is the color of the juvenile bulbs. If you purchase seeds, the bulb color should be advertised on the seed packet. If in doubt, plant the onion and wait for the bulb to grow so you can check what color onions you have planted. 


Onions are a great introductory crop to grow if you’re a beginning gardener in an area with a definite cold season, as they are low to the ground, great for shallow garden beds, and have fast and slow-growing varieties.

Moreover, here are the main points we discussed in this article:

  • Prior to buying onions, decide if you want to start with transplants, seeds or sets 
  • The onion life cycle as used by the backyard farmer includes germination, the seedling stage, the bulb growth stage, and maturation 
  • Whether you get a full-size common onion or a spring onion depends on when it is harvested. 

Don’t be afraid to dip your toe into a new area of gardening. Grow onions as a border around your garden, or in containers on your porch or back deck – the possibilities are endless! 

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