Onions are a versatile vegetable that can be grown in gardens across most of the United States. If you live in zone 7, you have the ideal climate needed to grow delicious onions from seed. This comprehensive guide will provide you with everything you need to know about the best time to plant onion seeds for a successful harvest in zone 7.
An Overview of Zone 7 Climate
The USDA Plant Hardiness Zone Map divides North America into 13 zones based on each region’s average annual minimum winter temperature Zone 7 has an average yearly minimum temperature of 0 to 10°F (-17 to -12°C).
Some of the key features of zone 7’s climate include
- Moderate winters with brief cold snaps
- Hot and humid summers
- Average last spring frost date of April 5th
- Average first fall frost date of October 21st
- Growing season of around 200 days
This temperate climate makes zone 7 ideal for growing a wide variety of fruits, vegetables, and ornamentals.
Why Grow Onions in Zone 7
Here are some of the top reasons you should consider adding onions to your zone 7 vegetable garden:
- Onions grow exceptionally well in zone 7. The moderate temperatures and long growing season allow ample time for bulbs to fully mature.
- You can harvest onions in zone 7 several weeks earlier than in cooler regions, fetching premium prices at market.
- Onions store well, providing you with homegrown flavor through winter after the growing season ends.
- Many sweet and mild onion varieties prefer zone 7’s warmer climate.
- Onions are easy to grow from seeds, sets, or transplants.
- Vertical growing area means onions are great for small spaces.
- Onions are an essential cooking ingredient, so having your own supply saves money.
Selecting the Best Onion Varieties for Zone 7
One of the keys to growing great onions is selecting varieties suited to your local climate. Here are some recommended onion cultivars for gardens in zone 7:
Short Day Varieties:
- Candy
- Southern Belle
- Granex 33 (Vidalia)
Intermediate Day Varieties:
- Super Star
- Gourmet
- Red Bull
Long Day Varieties:
- Copra
- Red Wing
- Red Baron
I suggest trying several onion types to see which perform best in your specific microclimate.
When to Plant Onion Seeds in Zone 7
Onion seeds can be planted in either spring or fall in zone 7:
Spring planting:
- Start seeds: March 1st – March 31st
- Transplant seedlings: Late March – Early April
Fall planting:
- Start seeds: Late September – Early October
- Transplant seedlings: Late October – Early November
Fall planting overwinters onions to get a head start on growth when spring arrives. Spring planting is best for seedlings or sets.
Starting Onion Seeds Indoors
Onion seeds can be sown indoors to give plants an early start before transplanting outside. Here are some tips:
- Plant seeds 8-10 weeks before your last expected spring frost date.
- Use a seed starting mix and sow seeds 1/4 inch deep.
- Keep soil moist and provide plenty of light.
- Thin seedlings to 1 inch apart after sprouting.
- Harden off plants for 7-10 days before transplanting outdoors.
Starting onions indoors leads to bigger bulbs at harvest time.
How to Direct Sow Onion Seeds Outdoors
You can also sow onion seeds directly in your garden bed:
- Prepare soil and mix in compost or fertilizer. Onions prefer nutrient-rich, well-draining soil.
- Create rows or thin furrows 1/4 – 1/2 inch deep and space 6-8 inches apart.
- Sow seeds closely together in rows.
- Cover with soil and water gently.
- Once seedlings are 2 inches tall, thin to 4 inches apart.
Consistent moisture is key to direct sowing success.
Onion Seedlings and Sets
For fall planting, onion sets or transplants are the best option as seeds need too much time to mature before winter.
Onion Sets:
- Small onion bulbs that establish quickly after planting.
- Sold by cultivar for easiest variety selection.
- Separate sets and plant 1-2 inches deep, 4 inches apart in rows.
Transplants:
- Choose disease-free seedlings around the size of a pencil.
- Harden off before planting.
- Transplant into rows 4 inches apart and 6 inches between plants.
- Water transplants daily for the first week.
Caring for Onions
Giving your onions the proper care and growing conditions will ensure a bountiful harvest. Here are some tips:
- Sunlight: Onions need full sun – at least 6 hours per day.
- Water: Keep soil moist, providing 1-2 inches per week. Consistent water is key.
- Weeding: Mulch around plants and stay on top of weeds. They compete for water and nutrients.
- Fertilizer: Use balanced fertilizer at planting and side dress with nitrogen mid-season.
- Pests: Watch for onion maggots, thrips and other pests. Use row covers if needed.
- Harvesting: When 75% of tops are brown and fallen over, pull bulbs and allow to dry before storing.
Storing Your Onion Crop
Properly cured onions can be stored for 2-3 months in zone 7:
- Allow onions to dry out of direct sun for 1-2 weeks after harvest.
- Cut back tops to 1-2 inches and roots to 1/4 inch.
- Cure bulbs for 2+ weeks in a warm, dry spot out of sunlight.
- Store cured onions in a cool, dry location around 40°F.
- Avoid storing onions in high humidity or wet conditions.
Enjoying Your Fresh Onion Harvest
The beauty of growing onions yourself is enjoying their flavor fresh from the garden. Here are some delicious ways to use your zone 7 onions:
- Chopped raw in fresh salads, salsas and guacamole
- Caramelized and added to sandwiches, burgers and pizza
- Sauteed or grilled as a side dish
- Added to soups, stews, chili and casseroles
- Pickled or brined
- Pureed into dips and spreads
Having your own supply of onions means you can experiment with recipes all season long. Any extras can be diced and frozen for using through the winter.
Troubleshooting Common Onion Problems
Growing a new type of vegetable always comes with a learning curve. Here are some potential issues and how to address them:
- Poor germination: Ensure soil is moist when sowing seeds. Start seeds indoors.
- Bolting: Plant resistant varieties and at the right times for your climate.
- Thin, small bulbs: Improper storage the prior year or lack of nutrients. Fertilize appropriately.
- Rotting: Avoid overwatering and harvest bulbs promptly once ready.
- Pest damage: Use row covers as needed to protect plants.
With proper preparation and care, you can overcome these challenges and grow a beautiful onion crop in zone 7.
Following the timing guidelines, variety selections, and growing tips in this article will set you up for onion growing success in zone 7. Pay close attention to choosing adapted onion types and sowing at the optimal spring or fall planting times. Provide attentive care through the season, and you’ll be rewarded with a plentiful harvest of delicious, homegrown onions.
How to Grow Onions From Seed
Once you’ve chosen your onion variety and done the math to know when to start your seeds indoors, you’re ready to go!
Be sure to choose the right container to start your seeds. Since they’re going to be growing for 16 weeks, it’s important they have enough space to develop the bulb size you’re looking for, so try not to plant too densely with the seeds.
Avoid starting them in shallow egg cartons or individual seed starting cells because potting up onion starts is not ideal or easy.
Melissa uses the large clamshell containers you buy lettuce in from the grocery store (pictured above) because they make a great greenhouse effect during germination when you close the lid.
- Fill your container with good quality potting soil (or soil from your garden if you’re sure it’s free from harmful bacteria or fungi).
- Sprinkle seeds generously all over the surface of the soil, then gently sprinkle a bit more potting mix over the seeds to just barely cover them.
- Dampen the soil with a spray bottle. Think “Goldilocks” here, not too moist, but not too dry. If the soil is dry to the touch, it’s time to water again. (We like to use a spray bottle to keep the seeds from moving around.)
- Seeds do not need sunlight until after they’ve sprouted, so keep the container in a semi-warm location (the top of the refrigerator or near a wood stove, etc.)
- Once they begin to sprout, set them under your grow lights, just as you would when starting other seeds indoors.
- When the green shoots of the onions reach about 6 inches, take a pair of scissors and cut the greens down to about 4 inches. As they continue to grow, keep trimming them so the energy can go into the bulb formation.
Why Grow Onions From Seed
Why would you grow onions from seed when purchasing and growing onion sets is so much easier? The quick answer is food security.
When you’re relying on someone else in order to grow your food supply, you’re not completely self-sufficient. When it comes to growing onions from seed, you’re eliminating one factor in your food supply and becoming more self-reliant.
The next step would be to learn how to harvest onion seeds, but we’ll discuss this more in a bit.
Growing Onions from Seed – Zone 7a
FAQ
When should I plant onions in zone 7?
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Spring Planting (for early summer harvest):
- Start onion seeds indoors 8-12 weeks before your area’s last spring frost date, which is typically in late winter.
- Transplant seedlings or plant starters outside in early spring when the soil is workable, about 2-4 weeks before the last spring frost.
- Alternatively, you can plant onion sets (small, immature bulbs) directly in the ground in late winter or early spring.
- Start onion seeds indoors 8-12 weeks before your area’s last spring frost date, which is typically in late winter.
-
Fall Planting (for early spring harvest):
- Direct sow onion seeds outdoors 6-8 weeks before your first frost.
- This allows the onions to overwinter and produce an early spring harvest.
- Direct sow onion seeds outdoors 6-8 weeks before your first frost.
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General Tips for Zone 7:
- Onions are cold-hardy and can tolerate frost, but prolonged freezing temperatures can damage them.
- Choose a sunny location with well-draining soil.
- Onions are heavy feeders, so amend the soil with compost or other organic matter before planting.
- Water regularly, especially during dry periods.
- Onions are cold-hardy and can tolerate frost, but prolonged freezing temperatures can damage them.
Which is the best month to sow onion seeds?
- The best time to sow onion sets is mid March to mid April.
- Sets can also be sown in Autumn from September to early October.
- You can also plant sets in modular trays which can be kept in an unheated greenhouse or tunnel for planting out when the weather allows from mid March.
How long do onions take to grow from seed?
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Timing:
- Start onion seeds indoors 6-8 weeks before the last expected frost.
- You can also direct sow seeds into the ground once the soil is workable, usually in late March to April.
- Start onion seeds indoors 6-8 weeks before the last expected frost.
-
Seed Starting:
- Use a pre-made seed starting mix.
- Keep the seeds warm and moist until they sprout, around 70 to 75°F (21 to 24°C).
- Once seedlings sprout, move them to a cooler spot and ensure they get ample light.
- Use a pre-made seed starting mix.
-
Transplanting:
- Transplant seedlings outdoors after the last frost, when they have 3-4 leaves.
- Transplant seedlings outdoors after the last frost, when they have 3-4 leaves.
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Growing Conditions:
- Onions need plenty of sunlight and well-drained soil.
- Ensure the soil is deep and loose, and fertilize regularly.
- Onions need plenty of sunlight and well-drained soil.
-
Harvesting:
- Onions are ready to harvest when the bulbs are fully grown and the tops fall over, usually around late summer.
- Onions are ready to harvest when the bulbs are fully grown and the tops fall over, usually around late summer.
Which month is best to plant onions?
| Season | Time of seed sowing |
|---|---|
| Tamil Nadu, Karnataka and Andhra Pradesh | |
| 1. Early Kharif 2. Kharif 3. Rabi | Feb.-April May-June Sept.-Oct. |
| Rajasthan, Haryana, Punjab, UP and Bihar | |
| 1. Kharif 2. Rabi | June-July Oct.-Nov. |