Growing Onions From Seed – The Complete How To Guide


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Growing onions from seed sounds prefer it is likely to be troublesome, but it surely actually isn’t. In this text, I’ll present you precisely when and how one can plant onion seeds and provide you with tons of tips about correctly caring for the seedlings.

How To Grow Onions From Seed & When To Start

It’s simpler to develop onions from seed than most individuals assume, and also you’ll have the very best choice of varieties to select from.

All it’s worthwhile to get began is a few fundamental tools and know-how, and I’ve shared all of it on this information.

Below you’ll discover detailed step-by-step directions for how one can plant and develop onion seeds.

Plus I provide you with important seedling care ideas so you possibly can preserve them wholesome from germination during transplanting them into your backyard.

Growing Onions From Seed

You can develop any sort of onion you need from seeds, so that you’ll have a a lot larger choice to select from than you’ll if you happen to purchased units.

Once the suitable sorts in your area, it’s enjoyable to experiment and discover those you like.

Types Of Onion Seeds To Plant

The most typical means we take into consideration onions is by colour: white, crimson, and yellow. But relating to beginning the seeds it’s vital to search out the suitable selection in your local weather.

They’re divided into three classes based mostly on the daytime they want.

  1. Long-day – These require 14+ hours of daylight per day. Some well-liked ones are Yellow Sweet Spanish, Red Wethersfield, Walla Walla, Yellow Gold, and Copra.
  2. Day-neutral – They want 12-14 hours of daylight, and embrace Candy, Red Stockton, Sierra Blanca, Cabernet, and Super Star.
  3. Short-day – Best for areas with 10-12 hours of solar. Choose Granex Yellow, Red Burgundy, Red Creole, Southern Belle, White Bermuda, or Texas Supersweet.
Onion seed packet
Onion seed packet

Best Way To Grow Onions From Seed

Many gardeners select to get a head begin on the rising season by beginning onion seeds indoors.

Some can take months to succeed in maturity, so it’s finest to plant them early if you happen to dwell wherever that has lengthy and freezing winters.

But you possibly can additionally attempt the direct planting or winter sowing strategies too, you probably have an extended sufficient season. Check out my publish on the totally different seed beginning strategies for more information.

How Long Does It Take To Grow Onions From Seed?

The variety of days it takes to develop onions from seed to reap can range broadly between the totally different varieties. But on common, the time from sowing to maturity falls someplace between 3-5 months.

You can all the time get pleasure from a few of your crop earlier nevertheless, they’re edible at any dimension. You can pull up younger ones and use each the tops and the bulbs in your recipes.

Mature onion in my garden
Mature onion in my backyard

When To Plant Onion Seeds

Exactly when it’s best to plant onion seeds is dependent upon the strategy you wish to use. Indoors, begin them 10-12 weeks earlier than your common final spring frost date.

To direct sow exterior, wait till the bottom is workable within the early spring, and the temperature is above 40°F. This is often a number of weeks earlier than your final frost date.

In hotter climates, you possibly can plant them immediately within the backyard within the fall or early winter.

Onion Germination Time

Though it may range relying on the setting, you possibly can anticipate to see your onion seeds germinating someday between 5-10 days after sowing them.

If it’s too chilly or moist, the method will be slowed. Keep the soil evenly moist however by no means soggy, and add backside warmth to assist velocity issues up.

What Do Onion Seedlings Look Like?

Right after they sprout, onion seedlings appear to be skinny inexperienced stalks that intently resemble chives. The leaves will get taller and thicker as they mature.

Baby onion seedling germinating
Baby onion seedling germinating

How To Care For Indoor Onion Seedlings

Properly caring for onion seedlings makes all of the distinction. Give them the very best mild, water, and occasional pinching to encourage robust roots.

If you encounter any points, learn my information on how one can repair widespread issues right here.


Once sprouted, onion seedlings will want 12 hours of sunshine a day. It’s laborious to attain this indoors, even with a sunny window. To keep away from legginess, I like to recommend utilizing a grow light set 1” above the tops.


They should be stored evenly moist always, however by no means in water-logged or soggy soil. Use a moisture meter that will help you get it good.


After three weeks you possibly can start utilizing a half-strength organic fertilizer as soon as per week. Compost tea or fish emulsion are additionally two nice choices.

Air Circulation

As quickly as they’ve sprouted, take away the plastic to encourage air move round them. You can even use an oscillating fan set on low close by to simulate wind and strengthen them.


Though you possibly can plant onion seeds in clusters, it’s finest to skinny them so there’s just one plant each 4-6” within the backyard, or one per cell or pellet indoors.

Potting Up

When seedlings have a minimum of three leaves every indoors, pot them up into bigger containers to encourage stronger root improvement. They transplant very effectively, so you possibly can use both plastic or plantable pots for them.

My onion seeds planted in a covered tray
My onion seeds planted in a coated tray

Transplanting Onion Seedlings Into The Garden

You can transplant your onion seedlings into the backyard when the soil is workable in early spring, and nighttime temps are above freezing.

Although they’re chilly tolerant, it’s vital to harden them off to allow them to alter to the weather, and survive the transition outdoor.

They can tolerate a lightweight frost, but it surely’s finest to cowl them if a late freeze is within the forecast.

Transplanting onion seedlings into the garden
Transplanting onion seedlings into the backyard


Here I’ve answered a few of the mostly requested questions on rising onions from seed. If yours isn’t on the checklist, please add it to the feedback part beneath.

How many onion seeds do you plant per gap?

You ought to plant 4-8 onion seeds per gap for the very best outcomes. Newer seeds have greater germination charges, so you should use much less if you would like.

How deep do you plant onion seeds?

Plant onion seeds no deeper than ¼”. They’re small and will not germinate in the event that they’re too far down.

Do onion seeds want mild to germinate?

Onion seeds don’t want mild to germinate, however the seedlings would require 12 hours a day as quickly as they start to emerge.

Are onions laborious to develop from seed?

Onions will not be laborious to develop from seed when you perceive their mild, water, and temperature wants.

Can I direct sow onion seeds?

Yes, you possibly can direct sow onion seeds in early spring, or as quickly because the soil is workable if you happen to dwell in a chilly local weather, or within the fall in hotter areas.

What month do you plant onion seeds?

The preferrred month to plant onion seeds varies based mostly on the place you reside. In chilly areas, begin them indoors 10-12 weeks earlier than your common final frost date. To direct sow, plant them 1-2 weeks earlier than the final frost.

Now that all of the steps, provides, and tips about rising onions from seed, you’ll be capable of get pleasure from any sort you want, and sort out it with confidence.

If you wish to study precisely how one can develop any sort of plant you need from seed, then it’s best to take my Seed Starting Course! It’s a self-paced on-line course that may stroll you thru every part step-by-step so that you don’t must wrestle to study by trial and error. Enroll and get began proper now!

On the opposite hand, if you happen to simply want a fast refresher on planting them indoors, then seize a replica of my Starting Seeds Indoors eBook.

More About Growing Seeds

Share your ideas for planting and rising onions from seed within the feedback beneath.

How To Grow Onion Seeds The Complete Guide

Steps For Planting Onion Seeds

In order to benefit from the largest yield, planting your onion seeds with care is vital. With a little bit of planning and the suitable instruments, it’s a lot simpler than you would possibly assume.

How To Plant Onion Seeds Step-By-Step

How To Grow Onions From Seed & When To Start

Once you understand how to do it, planting onion seeds is definitely quite simple. Gather your provides and comply with the steps beneath to make the method simple and easy.


    1. Prepare the soil – If you’re utilizing pellets, pre-moisten them earlier than putting them within the trays. Otherwise, use your trowel to fill every cell with damp soil mix. Outdoors, combine a slow-release granular fertilizer and natural compost into the mattress.
    2. Decide what number of seeds to plant – Onion seeds typically should not have a 100% germination fee, particularly older ones. They will be planted in clusters and are simple to separate or skinny out later. So for finest outcomes, plant 4-8 seeds per gap.Preparing to sow my onion seeds
    3. Sow the seeds – They’re small, so plant them no deeper than ¼”. You could make a gap and drop them in, or place them on prime and press them down gently into the soil. In backyard beds, dig shallow furrows and sprinkle them throughout in teams spaced 4” aside.
    4. Cover the seeds – Replace soil excessive and gently press it down so every seed has good contact. Take care to not push or compact the soil to keep away from slowing germination.Planting onion seeds indoors
    5. Water till moist – Lightly water the soil till it is evenly moist, however keep away from saturating it. It’s finest to water your trays from the underside to keep away from displacing the small onion seeds. A moisture gauge is a good instrument that will help you monitor the degrees extra simply.
    6. Cover the trays – Tent a plastic bag or dome lid excessive of your trays to entice moisture and warmth throughout germination.
    7. Keep them heat – The optimum soil temperature for onion seed germination is round 75°F. Place them someplace heat, like the highest of your fridge, or on a heat mat to hurry issues up. Use a soil thermometer that will help you keep a really perfect temp.

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