how to grow onions from seed

Easy Guide: How to Grow Onions from Seed

Onions are one of the most versatile and commonly used vegetables in many households. They are easy to grow, and the best part is that you can grow them right from seed! Growing onions from seed is an excellent way to not only save money but also to have a bountiful harvest of fresh, healthy onions. In this comprehensive guide, we will take you through the entire process of growing onions from seed, step by step.

Key Takeaways

  • Growing onions from seed is an easy and cost-effective way to produce a harvest of fresh and healthy onions.
  • Understanding the basics of onion seeds is crucial before delving into the growing process.
  • Proper germination, soil preparation, and maintenance practices throughout the growing season are essential for optimal onion plant growth.
  • Starting onion seeds indoors can be advantageous for shorter growing seasons.
  • Starting onion seeds directly in the garden can be a viable option for longer growing seasons.

Understanding Onion Seeds

Before you start planting onions from seed, it’s important to know a few things about onion seeds. The first step is to select high-quality onion seeds for planting. Choose seeds from a reputable supplier or save your own seeds from a previous harvest.

Next, prepare the soil for sowing the seeds. Onions grow best in loose, well-draining soil with a pH between 6.0 and 7.5. A soil test kit can help you determine the soil pH levels.

When sowing onion seeds, make sure to keep the soil consistently moist but not waterlogged. The ideal temperature range for germination is between 60 and 75 degrees Fahrenheit.

To sow onion seeds, simply scatter them on the soil surface and cover them with about ¼ inch of soil. For more precise sowing, you can make shallow furrows in the soil and space the seeds about ½ inch apart. Then, cover the seeds with soil and water well.

As onion seeds begin to germinate, ensure they are well-cared for through the process until they become healthy seedlings that can be transplanted into the garden.

Germinating Onion Seeds

As mentioned earlier, germination is a crucial step in growing onions from seed. To achieve successful onion seed germination, it’s important to provide the ideal conditions for the seeds to sprout.

Temperature and Moisture Levels

The ideal temperature range for germinating onion seeds is between 65°F and 75°F. It’s essential to maintain constant moisture during germination, but avoid overwatering which can lead to rotting of the seeds.

One way to ensure consistent moisture levels is by placing the seeds in a container with a moist soilless seed-starting mix. Cover the container with plastic wrap and place it in a warm location out of direct sunlight. The plastic wrap helps to retain moisture and create a greenhouse-like environment.

Challenges and Solutions

One of the common challenges of germinating onion seeds is low germination rates. In some cases, the seeds may not germinate at all. One possible reason for this is using old or low-quality seeds.

To increase your chances of success, purchase fresh, high-quality onion seeds from a reputable source. Another solution is to combine multiple seeds in a container to increase the chances of germination.

successful onion seed germination

Tip: Onion seeds can take up to two weeks to germinate, so be patient and consistent with moisture and temperature levels.

Following these best practices for germinating onion seeds can help ensure healthy seedlings and a successful onion harvest.

Transplanting Onion Seedlings

Transplanting onion seedlings is a crucial step in growing onions from seed. Here are some helpful tips to ensure your onion seedlings are transplanted correctly:

  1. Choose a well-draining spot in your garden for transplanting your onion seedlings.
  2. Make sure the soil is loose and fertile, and add compost if necessary to enrich the soil.
  3. Dig holes that are deep enough to accommodate the entire root system of each onion seedling, making sure to space them at least three inches apart.
  4. Water the soil in each hole prior to planting the onion seedlings.
  5. Gently remove the onion seedling from its container, being careful not to damage the roots.
  6. Place the onion seedling in the prepared hole and cover the roots with soil, firming the soil around the base of the seedling.
  7. Water the transplanted onion seedlings generously and keep the soil consistently moist until the plants become established.

Remember to mulch around the base of your transplanted onion seedlings to help retain soil moisture and prevent weed growth. With proper care, your onion seedlings will thrive and produce an abundant harvest.

Growing Onions from Seed Indoors

Growing onions from seed indoors can provide numerous advantages, particularly in areas with shorter growing seasons. Starting onion seeds indoors will allow for an earlier start to the growing season, which can result in a more extended harvest period.

To begin growing onions from seed indoors, first, select a suitable location and container. It is essential to ensure that the container has adequate drainage to prevent waterlogging. Use a high-quality seed starting mix and press lightly to level the surface before planting.

Plant seeds approximately 1/4 inch deep and cover with soil. Keep the soil moist but not too wet, and maintain a consistent temperature of around 70°F. Once the seedlings have germinated, you’ll need to thin them out and ensure that they have enough light, humidity and proper airflow.

An ideal location for growing onion seedlings indoors is a well-lit south-facing windowsill. However, supplemental lighting may be necessary in low-light conditions, such as cloudy days or northern exposure windows. You can use a grow light or fluorescent light to supplement natural light, providing up to 14 hours of light per day.

growing onions from seed indoors

Water seedlings regularly and monitor for any signs of disease or pests. A good practice is to transplant seedlings into the garden when they have reached a height of around 4-6 inches. This typically takes approximately 4-6 weeks from the initial seeding, depending on the variety of onion.

Overall, growing onions from seed indoors can be a fantastic way to extend the growing season and produce a bountiful and healthy harvest of onions.

Starting Onion Seeds Outdoors

Starting onion seeds outdoors is a great way to grow onions directly in your garden. This method is ideal for regions with a longer growing season and provides an opportunity to take advantage of natural sunlight and fresh air. In this section, we will cover everything you need to know about outdoor onion seed starting.

Soil Preparation

The first step in starting your onion seeds outdoors is soil preparation. Onions thrive in loose, well-draining soil that is rich in organic matter. Before planting, remove any rocks or debris and amend the soil with compost or well-rotted manure.

Expert Tip: Test your soil pH to ensure that it falls within the optimal range of 6.2 to 6.8 for growing onions.

Planting Depth

When planting your onion seeds, aim for a depth of 1/4 to 1/2 inch. Space the seeds approximately 1 inch apart and cover them with soil. Be sure to water the seeds immediately after planting.

Expert Tip: To improve germination rates, soak your onion seeds in warm water for a few hours before planting.

Essential Care Techniques

Once your onion seeds have sprouted, it’s essential to provide consistent care to ensure optimal growth. Water your onion seedlings regularly, but be careful not to overwater them as this can lead to disease. Fertilize every two weeks with a balanced fertilizer, and weed regularly to prevent competition with other plants.

By following these steps and taking proper care of your onion plants, you can expect a bountiful harvest of fresh, delicious onions straight from your garden.

Care and Maintenance of Onion Plants

Growing onions from seed can be a rewarding experience, but it requires proper care and maintenance to ensure optimal plant growth. Here are the best practices for caring for your onion plants:


Onions need consistent moisture to thrive, so be sure to water them deeply once a week if there is no substantial rainfall. Avoid overwatering, which can lead to disease and rot.


Onions benefit from regular fertilization throughout the growing season. Use a balanced fertilizer every three weeks, or opt for organic compost and apply it to the soil around the plants.

Weed Control

Weeds can compete with onion plants for nutrients and water, so it’s essential to keep the garden free of weeds. Hand-pull weeds as soon as you see them, or use a hoe to cultivate the soil around the onion plants.

Pest Management

Onion plants can be susceptible to various pests, including onion maggots and thrips. Monitor your plants regularly for signs of pest infestation and take appropriate action, such as using insecticidal soap or neem oil, to prevent damage.

  • Mulch around the onion plants to help retain moisture and suppress weeds.
  • Monitor for signs of disease, such as yellowing leaves or fungal growth, and promptly remove any affected foliage.
  • Harvest onions when the foliage turns yellow and falls over, and allow them to dry before storing.

By following these onion seedling care tips and best practices for growing onions from seed, you’ll be well on your way to a successful harvest of this delicious and versatile vegetable.


In conclusion, growing onions from seed is a rewarding and cost-effective way to produce an abundant harvest. By following the step-by-step instructions and tips outlined in this guide, you will be well-equipped to start growing your own onions from seed and enjoy the delicious results. Remember to select high-quality onion seeds, provide optimal growing conditions, and practice proper care and maintenance throughout the growing season.

Armed with this knowledge, you can confidently grow onions from seed indoors or outdoors, depending on your local climate and growing conditions. Whether you’re a novice or experienced gardener, growing onions from seed offers a satisfying and fulfilling gardening experience.

Thank you for reading our comprehensive guide on how to grow onions from seed. We hope you found it useful and informative. For more gardening tips and resources, be sure to check out our website. Happy gardening!

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