What Onions Grow in Tennessee: A Complete Guide to Choosing and Planting

Onions are a versatile and popular vegetable found in many home gardens. Tennessee’s climate and soil conditions make it an ideal location for growing a variety of onion types. Understanding the suitable onion varieties, planting techniques, and care methods is crucial to ensuring a successful harvest. In this article, we’ll cover everything you need to know about growing onions in Tennessee, including when to plant, how to care for them, and how to store your harvest.

Understanding Onion Varieties Suited for Tennessee

Short-Day, Intermediate-Day, and Long-Day Onions

Onions are classified based on the amount of daylight they need to form bulbs. In Tennessee, it’s essential to choose the right variety for optimal growth.

• Short-Day Onions: These onions require about 10-12 hours of daylight. They are suitable for areas with mild winters. Popular varieties include Texas Legend, Red Creole, and Southern Belle Red.
• Intermediate-Day Onions: Needing 12-14 hours of daylight, these onions are well-suited for Tennessee’s climate. Varieties like Super Star, Candy, and Red Candy Apple thrive here.
• Long-Day Onions: Requiring 14-16 hours of daylight, these onions are typically grown in northern regions. Varieties like Walla Walla, Copra, and Ailsa Craig can be grown in northern Tennessee, although they are not the best fit for most of the state.

Choosing the right variety based on day length is crucial for successful onion growing. For more information on the best onion varieties for your area, check out the Onion Variety Chart and Growing Guide.

Best Time to Plant Onions in Tennessee

Spring Planting

The best time to plant onions in Tennessee is during the early spring. Ideally, plant your onions once the soil temperature reaches at least 55°F. This ensures that the onion bulbs will have enough time to develop before the summer heat sets in. Planting should typically occur between late February and April, depending on the specific region and USDA hardiness zone within Tennessee.

Indoor Seed Starting

If you choose to start onions from seeds, it’s best to begin indoors about 8-10 weeks before the last expected frost date. The final frost dates in Tennessee vary by zone:

• Zone 5: March 5th
• Zone 6: February 24th
• Zone 7: February 6th
• Zone 8: January 23rd.

Starting seeds indoors ensures a longer growing season and better-established plants. To get started, fill seed trays with a quality seed-starting mix, sprinkle the seeds on top of the soil, and keep them in a warm, bright location.

Planting Directly in the Garden

For direct sowing, plant onion seeds or sets in the garden once the soil has warmed up and all danger of frost has passed, typically around late March or early April in Tennessee. Plant sets as early as possible for the largest onion development.

Preparing the Soil for Onion Planting

Proper soil preparation is vital for a healthy onion crop. Onions require well-drained soil rich in organic matter with a pH between 6.0 and 6.8. Here’s how to prepare your soil:

Soil Testing

It’s recommended to test your soil in the fall before spring planting. This can be done through the University of Tennessee Soil, Plant, and Pest Center. The test will help you determine the soil’s pH, structure, and nutrient levels.

Amending the Soil

Based on your soil test results, you may need to amend the soil with compost, manure, or lime to raise the pH. Spread a layer of amendments about 4 inches deep over your garden bed and mix it into the soil using a rake or spade.

Tilling the Soil

Till the soil to a depth of 12 inches to ensure proper root development. Onions have shallow roots, so it’s essential to break up the soil to allow for easy root penetration and nutrient absorption.

How to Plant Onions in Tennessee

Planting from Seeds

Planting onions from seeds allows you to choose from a wider variety of types. Here’s how to do it:

• Indoors: Start seeds indoors 8-10 weeks before the last frost. Sow seeds ½ inch deep in rows spaced 12 inches apart. Cover with soil and water well. Thin the seedlings to 2 inches apart once they emerge.
• Direct Sowing: Plant seeds 1 inch apart in furrows spaced 12-18 inches apart. Cover with a thin layer of soil, about ¼ to ½ inch deep.

Planting from Sets

Onion sets are small, immature onion bulbs. They are easier to plant and mature faster than seeds:

• Space sets 3-6 inches apart in rows spaced 12 inches apart.
• Plant sets with the pointed end up and the flat end down, 1 inch deep in the soil.
• Water immediately after planting to settle the soil around the sets.

Transplanting Onion Seedlings

If you started your onions indoors, transplant the seedlings into the garden once they are large enough to handle and the soil has warmed up. Space the seedlings 4-6 inches apart in rows spaced 12 inches apart.

Caring for Onions During the Growing Season

Watering

Onions need consistent moisture throughout the growing season. Water them regularly, providing about 1 inch of water per week. Avoid overwatering, as this can lead to rot and fungal diseases.

Fertilizing

Onions are heavy feeders and benefit from regular fertilization. Use a balanced fertilizer, such as 10-10-10, once a month during the growing season. Alternatively, apply a slow-release fertilizer according to package instructions.

Mulching

Apply a layer of organic mulch, such as straw or wood chips, around the base of the onion plants. Mulching helps conserve moisture, suppress weed growth, and regulate soil temperature.

Weed Control

Regularly weed the garden plot to keep weeds from competing with the onions for water and nutrients. Onions have shallow roots, so be careful not to disturb them while weeding.

Harvesting Onions in Tennessee

Onions are ready to harvest when the skins have turned brown and the bulbs are firm. This typically happens in late summer or early fall, about 100-120 days after planting, depending on the variety and growing conditions.

Steps for Harvesting

• Carefully dig up the bulbs with a garden fork.
• Gently push back the soil around the base of the onion bulbs to see if they have developed into mature bulbs.
• Once harvested, leave the onions on the ground for a day or two to dry out and cure in the sun. This will help toughen the skins and prolong the storage life of the onions.

Storing Onions

After the onions have cured, cut off the stems and roots to about 1 inch from the bulb. Store them in a cool, dry place with good air circulation. Onions should be stored in a place with a temperature between 32-40°F and low humidity.

Pest and Disease Management

Common Pests

• Onion Maggots: These pests lay eggs at the base of the onion plant, and the larvae feed on the roots, causing the plant to wilt and die. Use row covers to protect your onions from these pests.
• Thrips: Small, slender insects that feed on onion leaves, causing silvery streaks. Neem oil or insecticidal soap can help control thrips.
• Aphids: These small insects feed on the plant sap, weakening the plants. Use insecticidal soap or a strong jet of water to remove aphids.

Disease Prevention

• Avoid overwatering to prevent fungal diseases like downy mildew and neck rot.
• Remove any diseased plants from the garden immediately to prevent the spread of diseases.
• Practice crop rotation to reduce the risk of soil-borne diseases.

Frequently Asked Questions

When is the Best Time to Plant Onions in Tennessee?

The best time to plant onions in Tennessee is in early spring, once the soil has warmed up to at least 55°F. Planting usually occurs between late February and April, depending on the specific region and USDA hardiness zone.

What Type of Soil Do Onions Need?

Onions do best in well-drained soil rich in organic matter. The soil pH should be between 6.0 and 6.8.

How Deep Should I Plant Onions?

Onions should be planted about 1 inch deep for sets and ½ inch deep for seeds.

How Much Space Should I Give Each Onion Plant?

Onions should be spaced about 4-6 inches apart in rows spaced 12 inches apart.

How Much Water Do Onions Need?

Onions need regular watering, especially during dry spells. Water them deeply once a week, or more often if the weather is dry.

What Are the Best Ways to Protect Onions from Pests and Diseases?

To protect onions from pests and diseases, you can:

• Use row covers to protect against insects like onion maggots and thrips.
• Water the onions at the base of the plants to avoid splashing water on the leaves, which can spread diseases.
• Practice crop rotation and remove any diseased plants immediately.

When Should I Harvest Onions?

Onions are ready to harvest when the tops of the plants have fallen over and the skins have started to turn brown. Harvest typically occurs in late summer or early fall.

How Can I Store Onions?

After curing, store onions in a cool, dry place with good air circulation. Hanging them in mesh bags or braiding them is also effective. The optimal storage temperature is between 32-40°F with low humidity.

Conclusion and Additional Tips for Success

Growing onions in Tennessee can be a rewarding experience with the right preparation and care. By choosing the appropriate variety, planting at the right time, and providing consistent care, you can enjoy a bountiful harvest. Remember to:

• Select onion varieties suited for Tennessee’s climate, such as short-day and intermediate-day types.
• Prepare the soil properly, ensuring it is well-drained and rich in organic matter.
• Water and fertilize regularly, but avoid overwatering to prevent diseases.
• Protect your onions from pests using row covers and regular monitoring.
• Harvest and store onions correctly to ensure a long shelf life.