How To Plant Onion Starts [ Full Guide ]

Onion starts, also known as onion sets, are small, dormant onion bulbs that are used to grow onions. Planting onion starts is an easy and efficient way to kickstart the growth of onions in your garden. In this comprehensive guide, we will walk you through the process of planting onion starts, from choosing the right location to understanding the different types of onion starts, preparing the soil, and ensuring successful growth.

Quick Answer: How To Plant Onion Starts

  1. Choose the right location: Select a sunny location with well-draining soil.
  2. Understand the types of onion starts: Choose between green, yellow, or red onion starts based on your preference.
  3. Prepare the soil: Ensure the soil is loose, fertile, and has a pH between 6.0 and 7.5.
  4. Planting: Plant the onion starts about 1 inch deep and 4-6 inches apart in rows.
  5. Care and maintenance: Water regularly and keep weeds at bay.
  6. Harvesting: Harvest the onions when the tops have fallen over and started to dry.

Now, let’s delve into each step in more detail.

Choosing The Right Location For Planting

Selecting the right location is crucial for the successful growth of onion starts. Onions thrive in full sunlight, so it’s essential to choose a spot in your garden that receives at least 6-8 hours of direct sunlight daily. Additionally, ensure that the chosen area has well-draining soil to prevent waterlogging, as onions do not tolerate waterlogged conditions.

It’s also important to rotate your onion crop location every year to prevent the buildup of soil-borne diseases and pests. Avoid planting onions in areas where other members of the allium family, such as garlic or shallots, were grown in the previous year.

Understanding The Different Types Of Onion Starts

Before planting onion starts, it’s important to understand the different types available and choose the variety that suits your preferences and growing conditions.

Green Onions (Scallions)

Green onions, also known as scallions, are harvested when they are young and tender. These onions are characterized by their long, slender green leaves and mild flavor. They are popular for their use in salads, stir-fries, and garnishes.

Yellow Onions

Yellow onions are a versatile choice, known for their pungent flavor and ability to sweeten when cooked. They are a staple in many recipes and are excellent for cooking, caramelizing, and sautéing.

Red Onions

Red onions have a mild to sweet flavor and are known for their vibrant purple-red skin and rings. They are often used raw in salads, salsas, and sandwiches, adding both flavor and color to dishes.

When selecting onion starts, choose a variety that suits your cooking preferences and regional growing conditions. Additionally, ensure that the onion starts are firm and free from any signs of decay or damage.

Preparing The Soil For Planting

Onions thrive in loose, fertile soil with good drainage. Before planting, it’s crucial to prepare the soil to provide an optimal growing environment for the onion starts.

Soil Texture And Drainage

Onions prefer sandy or loamy soil that is well-draining. If your soil tends to retain water, consider adding organic matter such as compost or well-rotted manure to improve drainage and soil structure.

Soil Ph

Onions prefer slightly acidic to neutral soil with a pH between 6.0 and 7.5. You can test the pH of your soil using a soil testing kit and adjust it accordingly by adding amendments such as lime to increase pH or elemental sulfur to lower pH.

Soil Fertility

Prior to planting, incorporate a balanced fertilizer or organic amendments such as compost or aged manure into the soil to provide essential nutrients for the onions.

Soil Preparation Steps

  1. Clear the Area: Remove any weeds, rocks, or debris from the planting area.
  2. Loosen the Soil: Use a garden fork or tiller to loosen the soil to a depth of at least 6-8 inches to provide a loose growing medium for the onion roots.
  3. Incorporate Organic Matter: Mix in 2-4 inches of compost or well-rotted manure to improve soil structure and fertility.

By preparing the soil properly, you create an optimal environment for planting and ensure that the onions have access to the nutrients and moisture they need to thrive.

Planting Onion Starts

Now that the location has been selected and the soil prepared, it’s time to plant the onion starts. Follow these steps for successful planting:

Planting Depth And Spacing

Plant the onion starts about 1 inch deep in the soil. Space them 4-6 inches apart in rows, with rows spaced about 12-18 inches apart. This spacing allows the onions to have enough room to grow and develop without crowding.

Planting Process

  1. Create Furrows: Use a hoe or trowel to create straight, shallow furrows in the soil, spaced according to the desired row spacing.
  2. Place the Onion Starts: Gently place the onion starts into the furrows, ensuring that the tip of each start is facing upward.
  3. Cover the Onion Starts: Gently cover the onion starts with soil, ensuring that the soil is lightly packed around them to provide support.

Watering And Mulching

After planting, water the onion starts thoroughly to settle the soil and provide essential moisture. Consider applying a layer of organic mulch, such as straw or dried grass clippings, around the onion starts to help retain moisture, suppress weeds, and maintain a consistent soil temperature.

Care And Maintenance

Once the onion starts are planted, it’s important to provide proper care and maintenance throughout their growth cycle.


Onions require consistent moisture to develop healthy bulbs. Water the onion bed regularly, providing approximately 1 inch of water per week, either through rainfall or irrigation. Avoid overwatering, as excessively wet conditions can lead to rot and disease.


About a month after planting, you can consider applying a side-dressing of nitrogen-rich fertilizer to support the growth of the onions. Use a balanced fertilizer or organic nitrogen source and apply it according to the manufacturer’s instructions.

Weed Control

Keep the onion bed free from weeds, as they can compete with the onions for nutrients, water, and sunlight. Regularly remove any weeds that appear, being careful not to disturb the onion starts.


If the onion starts begin to overcrowd each other, you can thin them by carefully removing excess plants, allowing the remaining onions to have adequate space to grow.

Pest And Disease Management

Monitor the onion plants for common pests such as onion thrips, onion maggots, and diseases such as onion white rot. Consider using organic pest control methods and disease-resistant onion varieties to minimize potential issues.

Planting onion starts is a rewarding and straightforward process that can result in a bountiful onion harvest. By choosing the right location, understanding the different types of onion starts, preparing the soil, and providing proper care and maintenance, you can ensure the successful growth of onions in your garden. Whether you’re looking to grow green onions, yellow onions, or red onions, following these comprehensive guidelines will set you on the path to a successful onion harvest. Happy planting and may your garden yield a plentiful onion crop!

How To Properly Plant Onion Starts

Onions are a popular and versatile vegetable that can add flavor and depth to a wide range of dishes. While onions can be grown from seeds, many gardeners opt to start their onion plants from transplants, also known as onion starts. Planting onion starts can be a rewarding and efficient way to grow onions, as it allows gardeners to get a head start on the growing season and ensures the plants have a better chance of survival and growth.

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Planting onion starts requires attention to detail and proper techniques to ensure the plants establish themselves well. Follow these steps to plant your onion starts correctly:

1. Timing

Onion starts should be planted in early spring, after the last frost date for your area. The soil temperature should be around 50 to 55°F (10 to 13°C) when planting, as temperatures below this range may hinder germination and growth.

2. Selecting The Right Location

Choose a location in your garden that receives full sun for at least 6 to 8 hours a day. Onions require direct sunlight to grow and develop properly. Additionally, it is crucial to select well-draining soil to prevent onion rot and ensure optimal growth.

3. Preparing The Soil

Before planting, it is essential to prepare the soil properly. Start by removing any weeds or debris from the area. Dig into the soil to a depth of about 8 to 10 inches (20 to 25 cm) and loosen it thoroughly. Add organic matter, such as compost or well-rotted manure, to improve soil fertility and drainage.

4. Spacing And Planting Depth

Onions should be spaced about 4 to 6 inches (10 to 15 cm) apart. Dig a small hole for each onion start, ensuring it is deep enough to accommodate the roots without bending or overcrowding them. The hole should be around 1 inch (2.5 cm) deep. Gently place the onion start into the hole, making sure the top of the bulb is level with the soil surface.

5. Watering

After planting, water the onion starts thoroughly. The soil should be moist but not waterlogged. A deep watering right after planting will help settle the soil around the roots and encourage root establishment.

Watering And Caring For Newly Planted Onion Starts

Proper watering is crucial for the successful growth of onion starts. Here are some guidelines to follow:

1. Watering Frequency

Onion starts require consistent moisture to grow well. Water them thoroughly at least once a week, ensuring the soil is moist to a depth of 6 to 8 inches (15 to 20 cm). Depending on the weather conditions and soil type, you may need to adjust the watering frequency accordingly. It is crucial to avoid overwatering, as this can lead to rot and fungal diseases.

2. Mulching

Mulching onion starts can help conserve moisture, suppress weed growth, and regulate soil temperature. Apply a layer of organic mulch, such as straw or shredded leaves, around the onion plants, taking care not to cover the bulbs themselves. Mulch should be about 2 to 3 inches (5 to 7.5 cm) thick.

3. Weeding

It is essential to keep the onion bed free from weeds, as they can compete for nutrients and water. Regularly inspect the planting area and remove any weeds by hand. Be careful when weeding not to disturb the onion starts or damage their tender roots.

4. Thinning

As the onion starts begin to grow, they will produce foliage. If the plants are growing too close together, it may be necessary to thin them to ensure proper air circulation and prevent diseases. Thinning should be done when the plants are about 4 to 6 inches (10 to 15 cm) tall. Carefully remove the excess plants, leaving the remaining ones spaced approximately 4 to 6 inches apart.

5. Temperature Considerations

Onions prefer cool temperatures. If temperatures begin to rise above 75°F (24°C), consider providing shade to protect the plants. This can be done by using shade cloth or planting taller crops nearby to provide some relief from the direct sun.

Protecting Onion Starts From Pests And Diseases

Onion starts can be susceptible to various pests and diseases. Taking preventive measures is essential to protect them and ensure a healthy crop. Here are some methods to consider:

1. Pest Prevention

Onion maggots, thrips, and onion root maggots are common pests that can damage onion starts. To prevent these pests, cover your plants with floating row covers or insect netting, starting from the time of planting. These covers act as a physical barrier, preventing pests from reaching the onion starts. Remove the covers when the plants start to flower to allow for pollination.

2. Disease Management

Onions can be affected by diseases such as onion downy mildew and onion rot. To prevent these diseases, practice crop rotation by avoiding planting onion family plants in the same area for at least three years. Adequate spacing between plants and good air circulation can also help prevent the development and spread of diseases. Additionally, ensure proper watering techniques to avoid excessive moisture and reduce the chances of fungal infections.

3. Organic Pest Control

If you prefer organic pest control methods, consider using natural deterrents such as neem oil or insecticidal soap. These products can help control pests without harming beneficial insects or the environment. Apply according to the manufacturer’s instructions and make sure to target the pests directly.

Mulching And Fertilizing Onion Starts

Mulching and fertilizing are essential steps in ensuring the health and productivity of onion starts. Here’s what you need to know:

1. Mulching Benefits

Mulching not only helps conserve moisture and suppress weed growth, but it can also provide a steady release of nutrients as the mulch breaks down over time. Organic mulches, such as straw or shredded leaves, also improve soil structure and fertility.

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2. Applying Mulch

Apply a layer of mulch around the onion starts once they are established. Make sure the mulch is placed around the plants, leaving a small gap around the bulbs to prevent rot. A 2 to 3-inch (5 to 7.5 cm) layer of mulch is ideal for onions.

3. Fertilizing Needs

Onions have specific nutrient requirements for optimal growth. Before planting, it is recommended to amend the soil with organic matter, such as compost or aged manure, to provide a nutrient-rich foundation. Once the onion starts are established, side dress them with a balanced organic fertilizer, such as a 10-10-10 or 12-12-12 blend, according to the package instructions. Repeat this fertilization process every four to six weeks throughout the growing season.

4. Nitrogen Considerations

Onions have a high demand for nitrogen, which is essential for leaf and bulb development. If the foliage starts to turn yellow, it may indicate a nitrogen deficiency. In such cases, supplement with a nitrogen-rich organic fertilizer, such as blood meal or fish emulsion, following the recommended application rates.

Planting onion starts can be a successful and efficient method to grow onions in your garden. By following proper planting techniques, providing appropriate care, preventing pests and diseases, and mulching and fertilizing adequately, you can ensure healthy and productive onion plants. With patience and attention to detail, you can enjoy a bountiful harvest of flavorful onions to enhance your culinary creations. Happy gardening!

Tips For Successful Onion Start Growth

Onions are a versatile and essential ingredient in many culinary dishes. Growing your own onions can be a rewarding experience, and planting onion starts is a simple and efficient way to get started. Onion starts, also known as onion transplants or onion sets, are young onion plants that have been started from seed in a controlled environment. They are typically sold in bundles and are ready for planting in your garden or containers.

Planting onion starts offers several advantages over direct seed sowing. They give you a head start on the growing season, as they have already gone through the initial growth stage. They also have a higher success rate since they are more resilient to adverse conditions, such as extreme temperature variations or pests.

To ensure optimal growth and a bountiful onion harvest, consider the following tips:

1. Choose The Right Onion Variety

There are numerous onion varieties available, each with its own unique flavor and growing requirements. When selecting onion starts, choose varieties that are well-suited to your climate and growing conditions. Common onion varieties include yellow onions, red onions, sweet onions, and shallots.

2. Prepare The Soil

Onions thrive in loose, well-drained soil enriched with organic matter. Before planting, prepare your garden bed or containers by loosening the soil and removing any weeds or debris. Add compost or well-rotted manure to improve the soil’s fertility and drainage. Onions prefer a soil pH level between 6.0 and 7.0.

3. Plant At The Right Time

Onions are cool-season crops and should be planted when the soil temperature reaches around 50°F (10°C). Depending on your location, this is typically in early spring or fall. If you live in a colder region, you can start onion starts indoors 8-10 weeks before the last frost date. This allows them to establish their root system before being transplanted outside.

4. Proper Spacing

When planting onion starts, give each plant enough space to grow and develop. For larger-sized onions, space the starts 4-6 inches (10-15 cm) apart. For smaller onions or those intended for spring onion harvest, you can plant them closer together with a spacing of 2-3 inches (5-7 cm).

5. Planting Onion Starts

Gently separate the onion starts from their bundle, being careful not to damage the delicate roots. Dig a small hole in the prepared soil, deep enough to accommodate the roots of the onion start. Place the start in the hole, making sure the base of the bulb is level with or slightly above the soil surface. Firmly press the soil around the start to eliminate air pockets.

6. Adequate Water And Sunlight

Onions require consistent moisture for proper growth. Water the plants deeply, providing approximately 1 inch (2.5 cm) of water per week, either through rainfall or irrigation. However, be cautious not to overwater, as excessive moisture can lead to mold or rot. Onions also need full sun exposure, ideally receiving at least 6-8 hours of direct sunlight each day.

7. Fertilization

To promote healthy onion growth, apply a balanced fertilizer before planting the starts. This will provide the necessary nutrients that may be lacking in the soil. Additionally, you can supplement the growth with a side dressing of nitrogen fertilizer 3-4 weeks after planting. Be cautious not to over-fertilize, as excessive nitrogen can produce lush foliage at the expense of bulb development.

8. Mulching

Mulching your onion bed can help conserve moisture, suppress weed growth, and regulate soil temperature. Apply a layer of organic mulch, such as straw or compost, around the newly planted starts, taking care not to cover the plants’ base or foliage. Mulching also assists in preventing soil crusting, which can inhibit proper bulb formation.

Knowing When And How To Harvest Onion Starts

1. Assessing Onion Readiness

Onions are ready for harvest when the foliage starts to yellow and topple over. This usually occurs in late summer or early fall, depending on the variety and planting time. It is crucial to keep an eye on the plants during this stage to prevent over-maturity or bolting, which affects the quality and storage life of the onions.

2. Lifting And Curing The Onions

To harvest the onions, gently loosen the soil around the bulbs with a garden fork or trowel. Lift the bulbs out of the ground, ideally during a dry period, to facilitate proper curing. Avoid pulling the plants forcefully, as it may damage the bulbs or result in separation from the foliage.

After lifting the onions, lay them in a single layer on a clean, dry surface, such as a mesh screen or a wooden rack. Allow them to cure in a warm, well-ventilated location for about 2-3 weeks. Curing is essential for proper drying and preservation, enabling the outer layers to toughen and the necks to dry fully.

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3. Trimming And Cleaning The Onions

Once the onions have cured, they are ready for trimming and cleaning. Remove the dry foliage, leaving approximately one inch (2.5 cm) of the neck attached to the bulb. Trim the roots, ensuring they are clean and free of excess soil. It is crucial to handle the onions gently during this process to prevent bruising or damage.

4. Storing The Harvested Onions

Proper storage is key to extending the shelf life of onions. There are several methods to consider:

  • Curing onions for long-term storage: If you wish to store onions for an extended period, choose onions with dry and papery outer skins. Place the cured onions in mesh bags and hang them in a cool, dry, and well-ventilated location, such as a basement or pantry. Ensure the onions are not touching and have good airflow around them.

  • Storing onions in a cool, dark place: For medium-term storage of a few months, clean, dry, and unblemished onions can be stored in mesh bags, baskets, or well-ventilated containers. Keep them in a cool (around 40-50°F or 4-10°C), dark location, such as a root cellar or garage.

  • Freezing or canning onions: If you have an abundance of onions or prefer a convenient storage method, consider freezing or canning them. Prior to freezing, blanch the onions in boiling water for a few minutes, cool them in ice water, and then freeze in airtight containers. Similarly, onions can be pickled or canned in vinegar-based solutions for longer-term storage.

  • Using fresh onions promptly: If you have a limited storage space or prefer to use onions fresh, select the onions with intact skins and use them within a few weeks. Store them in a cool, dry place away from direct sunlight.

It is important to regularly check stored onions for signs of spoilage. Remove any onions that show signs of rot or disease to prevent them from spreading to others.

Troubleshooting Common Issues With Onion Starts

While growing onion starts is generally straightforward, several issues may arise. Here are some common problems and their solutions:

1. Bolting

Bolting refers to the premature formation of a flowering stalk, diverting the plant’s energy away from bulb development. This can occur due to temperature fluctuations or other stress factors. To minimize the risk of bolting, choose onion varieties that are less prone to bolting and plant them at the appropriate time for your location. If temperature fluctuations occur after planting, provide shade or cover the plants with row covers to protect them.

2. Onion Maggots

Onion maggots are small white fly larvae that feed on the roots of onion plants, causing stunted growth and wilting. To prevent onion maggot infestation, practice crop rotation and avoid planting onions near crops susceptible to the same pests, such as carrots or cabbage. You can also lay a floating row cover over the onion bed to create a physical barrier against flies.

3. Fungal Diseases

Onion plants are susceptible to fungal diseases such as onion downy mildew and white rot. To prevent fungal infections, avoid overhead watering, as wet foliage encourages disease development. Provide adequate spacing between plants to promote air circulation and reduce humidity. If fungal diseases are present, remove and destroy infected plants to prevent further spread.

4. Thrips

Thrips are tiny, slender insects that suck the sap from onion leaves, causing silver streaks or discoloration. To control thrips, regularly inspect the foliage for signs of infestation and crush any visible insects. You can also attract beneficial insects, such as ladybugs or lacewings, to prey on thrips. In severe cases, consider using organic insecticidal soap or neem oil according to the manufacturer’s instructions.

5. Weeds

Weeds compete with onion plants for nutrients, water, and sunlight. Keep the onion beds weed-free by regularly hand-weeding or using a shallow hoe. Applying a layer of organic mulch, such as straw or wood chips, can also suppress weed growth and conserve soil moisture.


Planting onion starts is a fantastic way to kickstart the growing season and ensure a successful onion harvest. By following the tips outlined in this guide, you can ensure the healthy growth of your onion starts, from planting to harvesting and storing. Remember to choose the right onion variety, prepare the soil properly, provide adequate water and sunlight, and address any issues that may arise promptly. With a little care and attention, you can enjoy a bountiful supply of fresh, homegrown onions for all your culinary delights.


What Is The Best Time To Plant Onion Starts?

Onion starts should be planted in the early spring, as soon as the soil is workable and temperatures consistently reach above 50 degrees Fahrenheit. This is usually around 4-6 weeks before the last frost date in your area.

How Do I Prepare The Soil For Planting Onion Starts?

Onions thrive in well-drained, nutrient-rich soil. Before planting, amend the soil with compost or well-rotted manure to provide adequate nutrients. The soil should also be loose and free of large clumps to allow for proper root growth.

How Much Space Should I Leave Between Onion Starts?

Onion starts should be spaced about 3-4 inches apart in rows, with 12-18 inches between each row. This spacing allows for proper growth and prevents overcrowding, which can lead to smaller onions.

How Often Should I Water Onion Starts?

Onion starts should be watered regularly, about 1-2 inches per week. However, do not overwater as onions do not like soggy soil. Allow the top inch of soil to dry out between watering.

How Do I Care For Onion Starts After Planting?

After planting, keep the soil moist but not waterlogged. Mulch can be added around the plants to help retain moisture and suppress weeds. Fertilize with a balanced fertilizer every 2-3 weeks. As the bulbs start to form, gently push the soil away from the bulb with your fingers to expose it to sunlight and encourage growth.