9 Onion Growth Stages Uncovered: (Seed to Mature Plant)

Welcome to the fascinating world of onions, where tiny seeds hold the promise of transforming into robust, pungent bulbs that add flavor and depth to our culinary creations.

Have you ever wondered about the journey an onion takes, from the humble seed to becoming a mature plant?

In this blog post, we will unveil the onion growth stages, shedding light on the remarkable transformations that occur beneath the soil and above.

Join us as we delve into the secrets of onion cultivation, exploring each phase of development, and gaining a deeper understanding of the factors that contribute to a thriving onion harvest.

Whether you’re a gardening enthusiast or simply curious about the wonders of nature, get ready to embark on a captivating journey as we uncover the mysteries behind onion growth stages, unveiling the extraordinary journey from seed to mature plant.

Some Basic Info About Onions:

Scientific NameAllium cepa
OriginCentral Asia
TypesRed, yellow, white, sweet, shallots
NutrientsHigh in vitamin C, fiber, and antioxidants
CaloriesApproximately 40 calories per 100 grams
FlavorRange from pungent to sweet, depending on variety
Culinary UsesRaw in salads, cooked in various dishes, pickled
Health BenefitsSupports heart health, boosts immunity, anti-inflammatory properties
Storage TipsStore in a cool, dry, and well-ventilated place
SeasonAvailable year-round

How Long To Grow:

Onions have a far longer developing season requirement than many different lawn veggies. This longer season is because of the time it takes for flowers to shape bulbs.

It takes a hundred to one hundred seventy five days for it to move from seed to a mature, dry bulb relying upon the range and nearby developing conditions.

Related: Do Onions Grow Underground? (Unveiling the Mystery)

Below is the table showing an approximate duration of growing onions:

Growth StageAverage Duration
Seed Germination7 to 10 days
Seedling Growth4 to 6 weeks
Bulb Formation4 to 6 weeks
Bulb Maturation3 to 4 weeks
Harvesting90 to 120 days
Please note that these durations are approximate and can vary based on factors such as onion variety, climate, soil conditions, and cultivation practices.

Read More: 12 Tomato Growth Stages Explored: (Complete Life Cycle)

Onion Growth Stages and Development:

Like carrots, domestic gardeners commonly develop onions as an annual crop, harvesting flowers whilst the bulb is mature, and the vegetative tops start to die.

In reality, though, Allium cepa are biennial flowers, which means it takes developing seasons to move from a germinating seed to a plant that produces its personal seeds.

Even if you plan to plant onions yearly, permit’s to smash the character growth degrees down into separate seasons.

You may find this video guide on growing onions from start to finish helpful!

Video Credits: GrowVeg

Year 1:

The first year in an onion’s existence cycle specializes in developing the tops and bulb development. Since maximum gardeners harvest their bulbs withinside the first season, those growths are the most effective ones they understand approximately.

1. Planting:

Onions are taken into consideration as a cool-season vegetable. They may be planted at exclusive instances of the year, relying upon your developing zone.

Gardeners in northern latitudes plant then in early spring for an overdue summer time crop. Gardeners in southern latitudes plant them withinside the spring or the fall.

a woman hand planting a organic onion seed
A woman hand planting a organic onion seed

For spring planting, intention to get transplants or plant onion units to your lawn beds whilst the soil temperature is always above 28℉.

This is commonly overdue March or early April, earlier than the remaining frost date of the spring. If you’re developing from seed, plant the seeds eight to ten weeks beforehand.

For fall planting, intention for planting units in August or September, giving them six to 8 weeks to develop earlier than the temperatures begin to fall. As the cool climate settles in, they pass dormant, resuming growth withinside the spring.

Once you plant your seeds, hold the soil wet in any respect. Seeds able to germinate include each embryo and meal reserves inside their protecting seed coat. Soil moisture softens the seed coat and enters the seed via a system name imbibition. Once in the seed, the moisture triggers cell respiration and metabolization of the meal’s reserves.

You can assume your seeds will germinate in approximately ten days.

2. Germination:

The first step in germination is the emergence of the radicle via the seed coat. Also referred to as the number one root, its task because the first rising root is to anchor seedlings withinside the soil and aid the plant. Once the radicle emerges, it absorbs moisture and vitamins from the soil to pressure plant growth.

3. Sprouting:

As the radicle begins off evolving soaking up vitamins and soil moisture, the primary shoot develops and emerges via the softened seed coat.

Fresh green onions sprouting in a container
Fresh green onions sprouting in a container

Gravitational forces obviously direct the shoot to develop upward via the soil, accomplishing for the sun. Once the shoot breaks via the soil floor, the seedlings alternate cognizance, and flowers direct their strength to growing leaves.

Also Check: Potato Growth Stages Unveiled: (From Planting to Harvest)

4. First True Leaf Forms:

The plant nevertheless is based on meals from the endosperm, so the growth of the seedlings is fantastically slow. With reserves dwindling, the seedlings are operating difficult to shape leaves. The first authentic leaf appears, a smaller model of the flat inexperienced leaves visible on a mature plant. Photosynthesis starts off evolving, and seedlings begin generating glucose for meals.

Seedlings at this degree seem like what we understand as immature onions and may be harvested now in case you want immature onions for a recipe.

5. “Leek” Stage:

With the capacity to photosynthesize, the plant’s growth choices increase at a speedy pace. As the seedlings grow new, undifferentiated cells, plant growth hormones paintings to show the cells into new leaves.

Each new set of leaves will grow the fee of photosynthesis, using growth. At this time, the neck of the seedlings starts off and evolves to thicken.

This degree encompasses the time from forming the primary authentic leaf till the plant has 4 to 7 authentic leaves. If you’re developing to reap leeks otherwise you need a small onion, harvest now. If you’re developing bulbs, permit them to hold developing.

6. Bulb Initiation:

At this time, the developing onions start specializing in bulb initiation, with mild being the number one driving force at the back of initiation. At a minimum, the flowers want 4 leaves for bulbing to arise no matter weather conditions. Each new leaf that grows paperwork a scale that finally develops into a hoop or sheath of the bulb.

Beautiful red onion bulbs growing in a row
Beautiful red onion bulbs growing in a row

Different types are labeled with the aid of using the day length, or quantity of daylight the flowers want every day to “set” bulbs.

Long-day types require 14 to 16 hours of daytime and convey the biggest bulbs considering those sorts have extra time to grow leaves earlier than bulb initiation. Short-day types require 10 to twelve hours of daytime. Day-impartial sorts require 12 to fourteen hours of daytime.

7. Bulb Development:

Once eight to twelve leaves grow, the onion plant stops sending up new leaves and focuses all of its sources at the bulbing system. The formerly fashioned leaves keep growing and elongate, collecting extra floor space for photosynthesis. The leaf sheaths swell in length to shape the primary tissue of the bulbs.

At this point, the onions start to push the soil away and “pop” up out of the ground.

8. Maturation:

As bulbs method maturity, flowers reveal a physiological reaction referred to as “tops down.” This takes place due to the fact sources are moved from the tops (leaves) to the scales, inflicting the bulb length to swell. When sources are depleted withinside the leaves, the tops fall over and dry down, signifying the bulb is prepared to reap.

Related: Pumpkin Growth Stages Explained (From Seed to Harvest)

9. Vegetative Senescence:

When autumn temperatures drop and a difficult frost takes place, water withinside the foliage freezes. The sharp edges of the ice crystals rupture the cellular partitions, inflicting fluid to leak out.

With a loss of structural integrity withinside the cellular partitions and no fluid withinside the cells, the onion tops die returned to the soil floor.

Year 2:

Many domestic gardeners in no way permit their onions to see the second one developing season, so maximum are not acquainted with the plant’s formation of plant life and seeds.

But if onions are not harvested and are allowed to overwinter withinside the ground, they begin to develop the subsequent spring once more to set seeds and entire their existence cycle.

1. Vegetative Growth:

When springtime temperatures start to climb, onions begin actively developing once more. Hormones withinside the bulb cause cells to begin growing and elongating, much like whilst germination came about the preceding season. 

Since the foundation machine absolutely advanced the remaining yr, the plant can cognizance its strength completely on sending up a shoot to interrupt via the soil floor.

2. Flowering Stalk Emerges:

As the season heats up and air and soil temperatures begin to climb, the flowers start to bolt. Vegetative growth halts, and the plant quickly shoots up a flowering stem to put together for the cease of its existence cycle. Once the stalk is absolutely fashioned, buds develop, and a white or crimson flower blooms on the top.

3. Formation of Seeds:

Pollination of the showy, spherical flower heads with the aid of birds, bees, or butterflies causes seeds to shape. All of the nutrient reserves discovered withinside the bulbs are translocated from the onion bulbs upwards to the seeds, developing the meals reserve the seeds use for germination. At this stage you will notice woody and fibrous bulbs. 

4. Senescence:

Once seeds shape, the onion plant’s existence cycle has come complete circle. Since the onion directed a lot of its sources in the direction of growing seeds, there’s little left for similar plant growth. With little sources left and no want to hold developing, plant growth hormones result in the genes answerable for senescence, and the plant dies.

Frequently Asked Questions (FAQs):

How long does it take to grow onions?

Onions take 90 to 100 days to ripen from seed, or about 4 months. Set onions can be harvested in about 80 days or just under 3 months.

Do onions need a lot of watering while growing?

Onions need a lot of water, but the soil should never get excessively wet. The ideal water needed for the onion is that it should be watered once a week to a depth of 2.5 cm instead of lightly misting daily.

How many onions will grow under a single plant?

Only one onion can grow from an onion seed. Under usual conditions, an onion seed yields only one onion.

Which fertilizer is the best for onions? 

Onions need a high nitrogen source. Nitrogen-based fertilizers (ammonium sulfate or ammonium nitrate) should be applied at a rate of 1 cup per 20-foot row.

Wrapping Up!

In conclusion, we would say that onions are a must for every cuisine around the world and growing them is very easy. Though it takes time to grow them but in the end you have your own grown onions that are great in taste. 

We have discussed all the growth stages and important points that are related to onion growth. It is surely recommended to plant onions and care for them. We hope that you found this article useful and got all your queries cleared. 

Remember, the journey from seed to mature plant is an exciting one, and by mastering the onion growth stages, we set ourselves up for success in our quest for flavorful and abundant harvests.

Few More Related Articles:

Garlic Growing Stages (Here’s How Garlic Grows)

Carrot Growth Stages Explored: (From Seed to Harvest)

Lemon Tree Growth Stages (Complete Life Cycle Guide)


  • Keith Wilson

    Keith Wilson is a well-respected gardening expert and author with a passion for all things related to vegetable gardening. With years of experience in the horticultural industry, Keith has developed a deep knowledge of plant care and cultivation techniques that he shares through his writing.

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