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how long do onions take to grow from seed

Dr Ahsanur Rahman, PHD

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how long do onions take to grow from seed
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The onion seed, an essential component of the Allium cepa life cycle, begins as a small, compact bulb with layers of protective tissue enveloping the embryonic plant within. This bulb, often referred to as the seed bulb or seed coat, safeguards the genetic information necessary for the development of a mature onion plant. Composed of dry, papery layers, the outer casing shields the delicate inner layers where the embryo resides, shielding it from environmental factors.

When conditions are favorable, the onion seed undergoes germination. This intricate process involves the absorption of water by the seed, triggering biochemical changes that break dormancy and initiate growth. The stored nutrients within the seed bulb fuel the early stages of development, providing the necessary resources for the emergence of a sprout from the soil.

As the seedling progresses, it evolves into a young onion plant characterized by green shoots and a developing root system. Over time, the plant’s leaves expand, and a bulb begins to form beneath the soil surface. The bulb undergoes a complex process of enlargement and differentiation, eventually maturing into the familiar onion that is harvested for culinary use.

The onion’s journey from a compact seed bulb to a mature vegetable is a testament to the resilience and adaptability of this plant species. Its distinct layers, both protective and nourishing, contribute to the successful propagation of onions in diverse agricultural settings worldwide.

Onion 1

How to Grow Onions from Seed

Growing onions from seed is a rewarding endeavor that allows you to savor the satisfaction of nurturing these flavorful bulbs from the very beginning. In this comprehensive guide, we’ll take you through the step-by-step process of growing onions from seed, ensuring a successful and bountiful harvest.

  • Selecting the Right Seeds: The first step in growing onions from seed is selecting high-quality seeds. Opt for varieties that suit your taste preferences and are well-suited to your local climate. Consider factors such as disease resistance and storage capabilities to maximize your harvest.
  • Germination: Patience is Key: Onion seeds typically take 7 to 10 days to germinate. To kickstart this process, plant your seeds in a seed tray filled with a well-draining seed-starting mix. Keep the soil consistently moist, and provide warmth to encourage germination. Patience is key during this initial phase.
  • Transplanting Seedlings: Once your onion seedlings have reached a suitable size (usually about 2-3 inches tall), it’s time to transplant them into the garden or larger containers. Choose a sunny location with well-draining soil. Ensure the soil pH is between 6.0 and 7.5 for optimal growth.
  • Soil Preparation: Prepare the soil by adding organic matter, such as compost, to improve fertility and drainage. Onions thrive in loose, well-draining soil. Incorporate a balanced fertilizer before transplanting to provide essential nutrients for healthy growth.
  • Planting Depth Matters: Plant your onion seedlings at the right depth, approximately 1/4 inch deep. Planting at the correct depth ensures proper root development and stability. Space the seedlings about 4-6 inches apart to allow for bulb expansion as they grow.
  • Watering Wisely: Onions need consistent moisture for optimal growth. Water your seedlings regularly, especially during dry spells. Avoid overwatering, as onions are susceptible to rot in waterlogged conditions. Mulching around the plants helps retain moisture and suppress weeds.
  • Feeding Your Onions: Fertilize your onions every 2-3 weeks with a balanced fertilizer. This provides a steady supply of nutrients throughout the growing season. Be cautious not to over-fertilize, as this can lead to excessive foliage growth at the expense of bulb development.
  • Sunshine is Essential: Onions thrive in full sunlight. Ensure your garden or chosen growing area receives at least 6-8 hours of sunlight daily. A sunny location contributes to robust leaf and bulb development, resulting in healthier and more flavorful onions.
  • Addressing Common Challenges: Keep a watchful eye on potential challenges such as pests and diseases. Onion crops are susceptible to issues like onion thrips and fungal diseases. Regular inspection and prompt treatment with organic or chemical solutions can help safeguard your crop.
  • Harvesting Your Bounty: The moment of harvest arrives when the onion tops start to yellow and fall over. Gently pull the onions from the soil, allowing them to cure in a dry, well-ventilated area for a few days. Once cured, trim the tops and roots, and your homegrown onions are ready to grace your culinary creations.

growing onions from seed is a fulfilling journey that requires attention to detail and a bit of patience. By following these steps, you’ll be well on your way to cultivating a bountiful harvest of flavorful onions right in your own backyard. So, roll up your sleeves, embrace the joy of gardening, and enjoy the fruits of your labor as you savor the delicious, homegrown onions you’ve nurtured from seed to table.

Fresh onion microgreen with onion seeds on a white background

Time Frame for Red Onion Growth

The time frame for red onion growth can vary based on several factors, including the specific variety of red onion, growing conditions, and the desired size of the onions. However, I can provide you with a general overview of the typical time frame for red onion growth from planting to harvest:

  1. Planting: Red onions are usually grown from sets (small bulbs) or seeds. Planting time depends on your location and climate. In many regions, red onions are planted in the spring, as soon as the soil is workable. Some gardeners also plant them in the fall for a spring harvest.
  2. Germination: If grown from seeds, red onions typically take about 7-10 days to germinate. If grown from sets, they start growing immediately after planting.
  3. Seedling Stage: During the onion seedling stage, which lasts approximately 7-10 days, seeds germinate, giving rise to delicate green shoots. These early seedlings require consistent moisture, moderate temperatures, and adequate sunlight. Once established, they’ll enter a phase of vigorous growth, preparing for eventual transplanting or direct planting in the garden.
  4. Vegetative Growth: Red onions go through a period of vegetative growth, during which they develop their green tops and establish their root systems. This phase can last anywhere from 40 to 90 days.
  5. Bulb Formation: The bulb formation stage is crucial for red onions. It generally takes around 90 to 120 days from planting for red onions to develop mature bulbs. However, some smaller varieties might mature a bit earlier, while larger varieties may take longer.
  6. Maturation: Red onions are usually ready for harvest when the tops start to yellow and fall over. This typically occurs in late summer to early fall, depending on when they were planted.
  7. Harvesting: Once the tops have fallen over, you can harvest the red onions. Allow them to dry for a few days in the sun, then store them in a cool, dry place.

Keep in mind that these time frames are general guidelines, and actual growth may vary. Factors such as soil quality, weather conditions, and care practices can influence the growth rate of red onions. Additionally, some gardeners may choose to harvest onions at different stages for green onions or smaller bulbs.

Addressing Common Issues in Onion Growth

Common issues in onion growth include:

  1. Overwatering: Onions prefer well-draining soil. Excess water can lead to root rot.
  2. Underwatering: Inconsistent watering results in stunted growth and smaller bulbs.
  3. Poor Soil: Onions thrive in fertile, loose soil. Compacted or nutrient-deficient soil hampers growth.
  4. Pests: Onion flies and thrips can damage plants. Use insecticides or natural predators.
  5. Diseases: Fungal diseases like white rot may occur. Crop rotation and fungicides help prevent spread.
  6. Weed Competition: Weeds compete for nutrients. Regular weeding is essential.

Addressing these issues promotes healthy onion growth and robust harvests.

Forum Onions in the Garden

how long do onions take to grow from sets?

Onions grown from sets typically take about 80 to 100 days to reach maturity. This time frame can vary based on factors such as the specific onion variety, growing conditions, and local climate. It’s important to note that some smaller or quicker-maturing varieties may be ready for harvest in around 60 to 80 days, while larger or long-day varieties might take longer, up to 100 days or more. Keep an eye on the appearance of the onion plants, and harvest when the tops begin to yellow and fall over.

1. Planting Onion Sets

  • Duration: Onion sets typically take around 5 to 7 days to sprout after planting.
  • Planting Depth: Plant sets with the pointed side up, just below the soil surface, at a depth of about 1 inch.

2. Early Growth Phase

  • Duration: The initial growth phase continues for approximately 3 to 4 weeks.
  • Optimal Conditions: Provide well-draining soil and adequate sunlight to encourage robust early growth.

3. Bulb Development

  • Timing: After the early growth phase, onions from sets begin bulb development.
  • Patience is Key: This stage varies but typically takes between 3 to 4 months, depending on the onion variety.

4. Monitoring Onion Size

  • Observation: Keep a close eye on the size of the onions as they mature.
  • Harvest Readiness: Onions are usually ready for harvest when their tops start to yellow and fall over.

5. Tips for Success

  • Soil Considerations: Ensure well-draining soil to prevent waterlogged conditions that can affect onion development.
  • Fertilization: Apply a balanced fertilizer during the early growth phase to support healthy bulb formation.
  • Weed Control: Keep the area around the onion sets free of weeds to minimize competition for nutrients.

How to Grow Onions from Seed in Pots

To grow onions from seed in pots, follow these steps:

  1. Fill pots with well-draining potting mix.
  2. Sow onion seeds 1/4 inch deep and cover lightly.
  3. Keep soil consistently moist.
  4. Place pots in a sunny location.
  5. Thin seedlings to prevent overcrowding.
  6. Fertilize regularly with a balanced fertilizer.
  7. Transplant seedlings to larger pots if needed.
  8. When seedlings are 4-6 inches tall, transplant them into the garden or larger containers.

Note: Onions may be better suited to direct sowing in the ground, but growing them in pots is possible with proper care.

Frequently Asked Questions

What is an onion seed?

An onion seed is a small, embryonic plant enclosed in a protective seed coat. It is the result of the sexual reproduction of an onion plant, containing genetic information for growth. Onion seeds are used for propagation, allowing growers to cultivate onions from seedlings for subsequent transplantation into garden beds or fields.

Which onion seeds is good?

The choice of onion seeds depends on factors such as climate, desired flavor, and storage capability. Popular varieties include ‘Yellow Sweet Spanish’ for mildness, ‘Red Creole’ for spiciness, and ‘Walla Walla’ for sweetness. Choose seeds based on your location, taste preference, and the intended use of the onions.

Which onion is best?

The best onion depends on personal preference and culinary use. For a mild flavor, ‘Vidalia’ and ‘Walla Walla’ varieties are popular. ‘Red Burgundy’ and ‘Red Wethersfield’ offer a spicy kick, while ‘Yellow Sweet Spanish’ is versatile. Consider your taste preferences and the dish you’re preparing when selecting the best onion.

What are the 4 types of onions?

Four common types of onions are yellow onions, known for a balanced flavor and versatility; red onions, prized for their vibrant color and mild taste; white onions, with a milder flavor suitable for raw consumption; and sweet onions, such as Vidalia and Walla Walla, celebrated for their mild and sweet taste.

What is the typical growth timeline for onions from seed to harvest?

Onions take around 3-4 months from seed to harvest. They are typically planted in the spring and harvested in late summer or early fall. The growing timeline varies depending on the variety and growing conditions. Overall, it’s important to understand how long sycamore season to plan and care for your onion crop.


After curing, remove the tops and store the onions in a cool, dry place with good air circulation. Properly stored onions can last for several months. Remember to adapt these guidelines based on your specific onion variety and local conditions. Happy gardening!

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