When to Plant Onions in North Carolina to Double Your Harvest: The Ultimate Guide

A Candy Onion Tray
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(Last Updated On: December 7, 2023)

Knowing when to plant onions in North Carolina is key if you want to maximize your harvest. In some areas, you can only plant onions in the spring. However, in North Carolina, you can plant bulbing onions in the fall AND the spring.

Read on to learn exactly how I plant two big rounds of onion crops in my Certified Naturally Grown (TM) 1/2 acre garden. These methods work well for me, and they can work for you too! 

The First Batch of Onion Seedlings Starts in December of the Previous Year

Day Neutral Onions for Spring Planting

When I plant onions in the spring, I actually start them as seeds back in December, and I only plant “day neutral” or “intermediate day” onion seeds. At my latitude, intermediate day onions seeds are the only ones that will bulb properly when growing in spring/summer.

 

Plant Seeds in December

I want my onion plants to be nice and big by the time I plant them out into the garden mid-February, so I start them from seed on December 1st.

What You'll Need

There are a few items you’ll use over and over again when planting onions for a spring harvest (or fall harvest) so it’s a good idea to invest in quality items that will last. This way you can amortize the cost of your supplies over several seasons of use.

Seeds

For North Carolina, these spring planted onions will need to be intermediate day onions (also known as day neutral onions). I have planted the following varieties from these suppliers for YEARS and had great germination rates and huge bulbs.

My Pick for Spring Planted Onions!
Candy Onion Seeds- Hoss Tools Candy Onion Seeds- Hoss Tools
  • Big, sweet onions, often weighing over 1lb EACH
  • My husband has NO problem eating these onions, but store-bought onions give him heartburn
  • If you have had problems eating store-bought onions in the past, try growing your own!
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Cabernet Red Onion Seeds- Botanical Interests Cabernet Red Onion Seeds- Botanical Interests
  • Cabernet's' globe shape and burgundy skin make it a beautiful addition to your harvest
  • Enjoy the sweet flavor raw on salads or burgers, or cooked into a jam on toast or cheese
  • Typically 2-3" in diameter. Stores for up to 6 months Recipe for red onion jam inside packet
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Seed Starting Mix

Seed starting mix helps you out BIG TIME in this process, because a good mix is light, fluffy and it doesn’t make the seeds work very hard to push through the medium. This helps the seedlings devote more strength to putting down a sturdy root system.

My Pick for Home Gardens
Purple Cow Organics All Natural Seed Starter Mix-for Fast Germination and Vigorous Seedlings with Strong Root Systems for Indoor Home Gardens, 12 Quart Bag Purple Cow Organics All Natural Seed Starter Mix-for Fast Germination and Vigorous Seedlings with Strong Root Systems for Indoor Home Gardens, 12 Quart Bag
  • Light and Fluffy mix allows seedlings to easily germinate
  • Organic, without large pieces of organic matter to impede seedlings' growth
  • My #1 choice when growing for my home garden
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Supplies

Seed Starter Kit for Backyard Gardeners- Bootstrap Farmer Seed Starter Kit for Backyard Gardeners- Bootstrap Farmer
  • Included in this seed starter kit for gardeners are:
  • (24) 6-cell Plug Inserts,
  • (4) 1010 2.5" trays without holes,
  • and (4) 1010 6" Domes. 
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Bin for Holding Seed Starting Mix

You’ll need a bin of some kind to hold you seed starting mix so you can moisten it. These work well for me, and they are affordable.

Wekioger Versatile Storage Organizer Plastic Bins with Lid, 12 Quart Latching Box, Set of 1 Wekioger Versatile Storage Organizer Plastic Bins with Lid, 12 Quart Latching Box, Set of 1
  • Perfect size for mixing water into your seed starting mix
  • One person can handle this, even when full with soil and water
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How to Start Spring Onion Seeds

I moisten the seed starting mix, use it to fill my seed trays, and pack the soil into the trays so that there aren’t large air holes in the soil.

If you get large air pockets in the soil, your seeds will send roots into those air pockets, dry out, and die. You don’t want that, so be sure to pack the soil enough at the start.

Once the seed starting mix is tamped down, sprinkle 3-5 seeds per cell and cover with 1/8″-1/4″ of seed starting mix. Pat down the mix to ensure it’s contact with the seeds, water them well, and place them in a well-lit place to wait for them to germinate.

How to Care for Onion Seedlings Until Planting Time

It ‘s pretty easy to care for your onion seedlings for the 3 months it takes for them to grow big enough to plant out. Just be sure the onions get sun every day, moisten them regularly, and fertilize them with a watered down liquid fertilizer like AgroThrive every 3-4 weeks. You can grow them under grow lights or on your countertop. If you have a greenhouse like I do, you can also grow them in your greenhouse.

planting onions in spring in north carolina

How to Plant Your Onions

When it’s time to plant your onions, you want to plant them about 1/2″- 1″ inch deep, and 6 inches apart within each row. I typically plant them in 3 or 4 rows per 30″ wide garden bed, but I’ve also grown them in 2 rows per bed, as you can see below.

You can dig an individual hole per plant, or you can dig a shallow trench with a hoe and then lay out the onions in that single trench. I find the trench method is the fastest, but you can do whatever is the best for you.

At the time of planting, I amend my soil with Biotone Starter Plus by adding the equivalent of a teaspoon per plant in the bottom of the trench, similar to what you see below. Biotone Starter Plus is my pick for all around organic granular fertilizer when I’m planting out into the garden.

How to Take Care of Onions Until Harvest

After the first month- 6 weeks in the ground, I begin fertilizing with a high-nitrogen organic fertilizer every 3 weeks. I like blood meal or alfalfa meal for this. Or, I’ll use Agrothrive when I need to push fertilizer through the irrigation system. Once i see bulbing begin, I stop that nitrogen supplementation.

During this time, I do weed rather religiously if I’m not planting through paper mulch.

When to Harvest

When you begin to see the necks of the onions (where the stem meets the top of the bulb) start to get soft and flop over, that’s your cue to start paying attention! It’s almost time to start pulling. You can actually start pulling the ones that have flopped over, but ONLY those for now.

Once about half of your onions have flopped over, then you can push the rest of them over so that they are all ready to pull at the same time. Depending on when you planted the onions , this will happen sometime around end of May-through June.

How to Harvest

When harvesting, don’t just yank the onion by the top to get it out of the ground. That can damage the onion and sacrifice it’s storage life. Instead, go through and lift up from under the onions with a pitchfork or other garden tool. Then pull up on the onion and lift it up from the bottom at the same time.

Lay your onions flat in a relatively cool, dry, dark place for 2 weeks so that the onion necks can dry out and seal. after the necks are completely dry, you can cut off the tops leaving a few inches of stem, and store them in a cool, dry, dark place like your basement or root cellar.

The Second Batch of Onion Seedlings Starts at the End of July!

You just harvested the first batch of onions in North Carolina, and now it’s time to plant the seeds that will become your second batch of North Carolina onions!

We’ll give you a month or so to admire your work from the spring, and now it’s time to switch focus to your fall planting.

Local garden centers won’t have plants during this time, so it’s your time to really shine. I like to take this opportunity to plant onion varieties that I can’t get in plants or sets. This way, I can branch out and really experience new home grown tastes.

 

Short Day Onions for July Seeding

When to Plant onions in north carolina

Plant Seeds in July

You’ll plant seeds in July so that you can plant them out in the fall.

What You'll Need

Seeds

You’ll need a DIFFERENT type of onion seeds for fall planted onions than the onion types you started for spring planted onions.

In spring, we grew intermediate day onions, but for the fall planting timeline, you’ll start SHORT DAY onions. This is because day length is so short in the fall/winter that your onions would never bulb if you grew the same ones as for spring.

But don’t worry- I’ve got you. Even if you’ve never overwintered onions, you’ll rock this because I’m sharing my picks for best overwintered short-day onion varieties for North Carolina below.

Seed Varieties You Can Grow For Fall Planting

Savannah Sweet Onions- Hoss Tools Savannah Sweet Onions- Hoss Tools
  • Savannah Sweet Onion is a hybrid, short-day onion variety
  • Produces large, sweet onions that are golden yellow
  • A Vidalia-type variety that’s early maturing with a flattened, granex shape. Allium cepa. 125 days to maturity.
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Plethora Onion Seeds- Hoss Tools Plethora Onion Seeds- Hoss Tools
  • Jumbo yellow granex-type onion
  • Loves to planted in fall and overwintered
  • 180 days to maturity


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1015Y Texas Super Sweet Onion Seeds- Hoss Tools 1015Y Texas Super Sweet Onion Seeds- Hoss Tools
  • Routinely grow to over a pound
  • Large, sweet
  • 115 days to maturity
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Red Creole Onions

Red Creole Onion Seeds- Hoss Tools Red Creole Onion Seeds- Hoss Tools
  • 110 Days to Maturity
  • Crisp Texture with great onion flavor, wonderful eaten raw
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Seed Tray

The seed trays you’ll use for these plantings are the same ones you used above- nothing changes for this. If you didn’t see my recommendations above, go check them out.

Seed Starting Mix

Same goes for the seed starting mix- nothing changes here either. Just check above for my recommendation, or click here for Purple Cow Seed Starting Mix to save time.

How to Start Fall Onion Seeds

You’ll start your fall planted seeds the same way you planted your spring onion seeds. I describe that above, so I won’t repeat it here. Just check out how to start your onion seeds above when your ready to take that step.

How to Care for Your Onion Seedlings Until Planting Time

There ARE some aspects that are different about caring for your seedlings that you’ve just planted as compared to the ones you planted in the spring.

A big difference is that you don’t need a greenhouse or grow lights to start these onions in. Onions have so few natural pests that you don’t need to cover them like you would kale or other brassicas. They love full sun, so may times, I just start the seeds outside and let them grow that way. As long as they have plenty of water and sun, they will be fine. Before, when we planted the spring seeds, it was useful to have them inside because of cold temperatures.

How to Plant Your Onions

When I’m planting fall onions out into the garden, I do it just the way I do it in the early spring. I either plant them in individual planting holes or in a trench, depending on how many I have to plant. If I have more than a handful to plant, I’ll dig a shallow trench. Because I’m usually planting at least 100 onions at a time these days, I’ll usually dig the shallow trench.

 

When I’m overwintering onions in my zone 8A garden, I’ll plant them out into the garden sometime in November. Fall planted onions don’t “take off” like their spring counterparts, because temperatures are falling instead of rising, in general. This means that your onions will get off to a slower start, but that’s natural for this time of year.

How to Take Care of Your Onions Until Harvest

Use Shredded Leaves for Mulch as an Extra Blanket of Protection

You may want to give your fall planted onions some extra protection from cold temps, and I recommend adding straw or shredded leaves as mulch around your onions as soon as you plant them out.

Don't Fertilize Until First of February

When winter arrives, your soil temperatures will be very low until early spring, so it won’t do much good to fertilize the plants during this time. There is also less than 10 hours of sunlight during this time, so the onions will be in a sort of “dormant” state. Once the soil is warmer in late winter/ early spring, you can begin your high nitrogen fertilizer regimen. At that time, the nutrients in the fertilizer will be more bioavailable to the plants because of the warmer temps and higher microbial activity.

When spring arrives, your onions grow faster, and the competing weeds start to come on now. I’ve always heard that onions don’t like weeds, but I”m not sure I understand that statement. I’m thinking it has to do with their shallow root system that will naturally be forced to compete with weed roots. But not all weed roots are shallow… At any rate, pull your weeds when you see them and you’ll be good to go.

When to Harvest

The cues you’ll look for that tell you when to harvest are–you guessed it–the same as your spring planted onions.

When the onion crop starts to have soft necks (where the stem meets the bulb) that is your cue to begin paying attention to further signs of maturity. Once the onion tops begin to flop over, pull those onions and let them cure in a cool, dark, dry place. Once 1/4-1/2 of your onion tops start to flop over, you can push the rest of the tops over, pull them, and cure them.

 

How to Cure Your Onion Crop

You’ll cure your onions by laying them out in a single layer in a cool, dry, dark-ish place. Lay them out in a single layer so they dry instead of rot. Check them periodically to make sure the necks are drying out and not rotting. In about 2 weeks, your onions will be dry enough to store in their final storage location. I store mine in my cool basement and they last for months.

Stacks of onions curing. I had already cut the tops off the white onions and was about to start on the yellow.

Conclusion

As a gardener in North Carolina, understanding the optimal times and methods for planting onions is crucial for doubling your harvest. This comprehensive guide outlines a successful strategy for growing onions in both spring and fall, leveraging the unique climate of North Carolina.

Key Takeaways:

  1. Start Early for Spring Planting: Begin with day-neutral or intermediate day onion seeds in December. This early start ensures robust seedlings ready for mid-February to mid-March planting.

  2. Invest in Quality Supplies: Utilize high-quality seeds, seed starting mix, and planting trays. This initial investment pays off across multiple planting seasons.

  3. Effective Seed Starting: Moistening the seed mix and carefully planting the seeds avoids air pockets, promoting healthy root development. Regular sunlight, moisture, and fertilization are essential for nurturing the seedlings.

  4. Planting Technique: Plant onions 1/2″-1″ deep and 6 inches apart, using either individual holes or a trench method. Amending the soil with organic fertilizer like Biotone Starter Plus at planting enhances growth.

  5. Ongoing Care: Regular weeding and fertilization with high-nitrogen organic fertilizers are crucial until the bulbing process begins. For fall plantings, mulching with straw or shredded leaves offers additional protection.

  6. Harvesting and Curing: Harvest when the necks soften and tops flop over. Cure the onions in a cool, dry, dark place for two weeks before storage.

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