How To Get Seeds From Onion Bulb: A Proven, Effortless Way

To get seeds from an onion bulb, you must plant a cured onion bulb from the previous season. The bulb needs a cold period to trigger flowering. Once planted, it will grow a tall stalk with a flower head. After pollination, this head will dry out, revealing tiny black seeds that you can easily harvest, dry completely, and store.

Hello, fellow gardeners! It’s Md Saiful Islam, and today I want to share a little garden magic with you. Have you ever looked at an onion and wondered how to get seeds from it? It might seem like a secret known only to seasoned farmers, but I promise it’s one of the most rewarding and simple projects you can do. Many beginner gardeners think you just let an onion grow, but there’s a small trick to it.

Don’t worry, though. It’s not complicated! Forgetting one simple step is usually why people struggle. In this guide, I will walk you through everything, step-by-step. We will turn a single onion bulb into hundreds of seeds for next year’s garden. Let’s unlock the full life cycle of the humble onion together and make your garden even more sustainable.

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How To Get Seeds From Onion Bulb?

Before we dive into the “how,” let’s talk about the “why.” Taking the time to save your own onion seeds is more than just a fun experiment. It’s a wonderful way to connect more deeply with your garden and enjoy several great benefits.

Save Money: A single packet of onion seeds can be costly. When you save your own, one onion bulb can produce hundreds, sometimes thousands, of seeds. That’s enough for you, your friends, and your neighbors for seasons to come!
Grow Stronger Plants: Seeds saved from plants that grew well in your specific garden are already adapted to your soil, climate, and conditions. This means the next generation of onions will likely be even healthier and more resilient.

Preserve Amazing Varieties: Do you have a favorite onion variety that’s hard to find? By saving its seeds, you ensure you can grow it year after year. This is especially important for heirloom varieties, which are passed down through generations.
It’s Fun and Rewarding: There is a special kind of satisfaction that comes from seeing a plant through its entire life cycle, from bulb to flower to seed. It’s a beautiful process to witness and a fantastic learning experience for gardeners of all ages.

The Most Important Secret: Understanding the Onion’s Life Cycle

Here is the key piece of information that makes everything else fall into place. Onions are biennial plants. This fancy word simply means they have a two-year life cycle.

Year One: In its first year, the onion focuses all its energy on creating the bulb. We plant a seed, it grows leaves, and then forms the round, delicious onion underground that we love to eat. At the end of this season, we harvest the bulb.
Year Two: In its second year, the onion’s mission changes. Its goal is no longer to grow a bigger bulb but to reproduce. After a cold winter period, the planted bulb will use its stored energy to send up a flower stalk, produce flowers, and finally, make seeds.

So, to get seeds, we have to mimic this two-year cycle. We start with a fully grown onion bulb (from Year One) and trick it into thinking it’s time for Year Two.

Choosing the Perfect Onion Bulb for Seed Production

Not just any onion from the grocery store will do. For the best results, you need to be a little selective. Here’s what to look for when choosing your “parent” onion bulb.

1. Pick a Healthy, Firm Bulb

Your chosen onion should be in perfect condition. Look for a bulb that is:

Firm to the touch: Squeeze it gently. It should feel solid, not soft or squishy.
Free of blemishes: Avoid onions with cuts, bruises, or soft spots.
No signs of mold or rot: Check the top and bottom for any fuzzy or dark spots. A healthy onion is a strong foundation for healthy seeds.

2. Choose an Open-Pollinated or Heirloom Variety

This is an important point for long-term seed saving. Onion varieties are either “hybrid” or “open-pollinated.”

Open-Pollinated (and Heirloom): These are the best choice. Seeds from these onions will grow into plants that are “true to type,” meaning they will look and taste just like the parent onion.
Hybrid (Often Labeled F1): These are created by cross-pollinating two different parent varieties. While the first-generation onion is fantastic, its seeds are genetically unstable. If you plant them, you might get onions that are very different from the parent, or they may not grow well at all.

If you grew your own onions from seed, you likely know the variety. If you’re buying one, check a farmers’ market where the grower can tell you exactly what it is.

Gathering Your Simple Tools and Materials

You don’t need any fancy equipment for this project. You probably have most of these things already!

A healthy onion bulb: Your chosen parent onion.
A pot or garden space: A pot at least 8 inches deep will work, or you can plant it directly in your garden bed.
Good quality potting soil or compost: To give your onion the nutrients it needs.
A small trowel: For digging.
A watering can or hose: For gentle watering.
A pair of scissors or pruners: For harvesting the seed head.

A paper bag: Essential for drying the seeds without losing them.
A sunny spot: Onions need at least 6-8 hours of direct sunlight per day to produce strong flowers.

Step-by-Step Guide: How to Get Seeds From an Onion Bulb

Alright, let’s get our hands dirty! Follow these simple steps, and you’ll be on your way to a jar full of onion seeds.

Step 1: The Critical Cold Period (Vernalization)

Remember the onion’s two-year life cycle? To trigger flowering, the bulb needs to experience a period of cold, just like it would during winter. This process is called vernalization. Without it, your onion will likely just grow more green leaves instead of a flower stalk.

You have two easy options:

The Natural Way: If you live in a climate with cold winters, you can plant your onion bulb in the garden in the fall. It will overwinter in the ground and sprout in the spring, ready to flower.
The Fridge Method: If you have a stored onion bulb in the spring, you can simulate winter yourself! Place the onion bulb in your refrigerator’s crisper drawer for at least 4-8 weeks. Do not put it in the freezer, as that will kill the bulb. This cold treatment signals to the onion that it’s time to start its second-year growth.

Step 2: Planting Your Onion Bulb

Once your onion has had its cold treatment, it’s time to plant it. The best time is in early spring, as soon as the soil can be worked.

Prepare the Spot: Whether in a pot or the garden, make sure the soil is loose and well-draining. Mix in some compost for an extra nutrient boost.
Dig the Hole: Dig a hole that is about twice the depth of the onion bulb.

Plant the Bulb: Place the onion bulb in the hole with the pointy side up (where the leaves would sprout) and the root side down.
Cover with Soil: Gently cover the bulb with soil so that just the very tip is peeking out. Pat the soil down lightly.
Water Gently: Give it a good, gentle watering to help it settle in.

Step 3: Caring for Your Flowering Onion Plant

Now, you get to watch the magic happen. Your job is simply to provide basic care, just like you would for any other garden plant.

Sunlight: Make sure your onion gets plenty of sun. Full sun is best.

Watering: Keep the soil consistently moist but not waterlogged. Water at the base of the plant to avoid getting the leaves too wet.
Watch it Grow: First, you’ll see green shoots emerge. Then, a thick, round stalk will begin to grow from the center. This is the flower stalk, also known as a scape. It can grow quite tall—sometimes up to 3-4 feet!
The Flower Head Forms: At the top of the stalk, a papery sheath will form. This will eventually burst open to reveal a beautiful, globe-shaped flower head called an umbel. It’s made up of dozens of tiny, individual white or purplish flowers.

Step 4: Let the Pollinators Do Their Work

Once the flowers open, you’ll notice bees, flies, and other insects visiting them. This is fantastic! They are your little garden helpers, moving pollen from flower to flower. Pollination is necessary for seeds to form. You don’t need to do anything here except enjoy watching nature at work. For this reason, avoid using any pesticides on or near your flowering onion.

If you’re interested in the details of how plants are pollinated, the U.S. Forest Service has a wonderful resource on pollinators and their importance.

Step 5: Knowing Exactly When to Harvest the Seed Head

Patience is key during this stage. You must let the seed head mature and dry completely on the plant. Harvesting too early will give you seeds that won’t sprout.

Here’s what to watch for:

The flowers will fade and die back.
The green, globe-shaped head will start to turn brown and feel dry and papery.
The stalk just below the head will begin to weaken and may start to bend over.
If you look closely, you will see tiny, black seeds inside the dried flower pods. Some might even start to fall out when the wind blows. This is the perfect time to harvest!

The entire process from flowering to seed maturity can take several weeks, so keep a close eye on it.

Stage	What to Expect	Approximate Time
Planting Bulb	Planting the vernalized onion bulb in spring.	Day 1
Sprouting	Green shoots emerge from the soil.	1-2 Weeks
Flower Stalk Growth	A tall, thick scape grows from the center.	3-5 Weeks
Flowering	The umbel (flower head) opens and blooms.	6-8 Weeks
Seed Maturation	Flowers fade, and the seed head dries on the stalk.	10-14 Weeks
Harvest	The head is brown, dry, and seeds are visible.	14-16 Weeks

Step 6: Drying, Threshing, and Cleaning Your Seeds

Once the seed head is ready, it’s time for the final steps. This part is easy and very satisfying.

Cut the Stalk: Using your scissors, cut the flower stalk about 6-8 inches below the head.
Place in a Paper Bag: Place the seed head upside down inside a paper bag. Tie the top of the bag loosely around the stalk with a piece of string. This will catch any seeds that fall out as it continues to dry.
Hang to Dry: Hang the bag in a cool, dry, and well-ventilated place for another 1-2 weeks. You want to make sure the seeds are completely dry before storing them.

Thresh the Seeds: “Threshing” is just a simple term for separating the seeds from the plant. Once fully dry, simply shake the bag vigorously. You can also gently crush the dry flower head with your hands inside the bag. The tiny black seeds will fall to the bottom.
Clean the Seeds (Optional): Pour the contents of the bag onto a plate. You’ll have a mix of seeds and chaff (dried flower parts). You can gently blow across the plate to remove the lighter chaff, leaving the heavier seeds behind. This is called “winnowing.”

Step 7: Storing Your Onion Seeds for Future Success

Proper storage is crucial for keeping your seeds viable for the next planting season. Seeds need to be kept cool, dark, and dry.

Choose a Container: A small paper envelope, a glass jar with a tight-fitting lid, or a small resealable plastic bag will work perfectly.
Label Everything: This is a step you will thank yourself for later! Label your container with the onion variety and the date you harvested the seeds.
Find a Good Spot: Store the container in a cool, dark place like a cupboard, a drawer, or a closet. Avoid places with fluctuating temperatures or high humidity, like a kitchen or bathroom.

When stored properly, onion seeds can remain viable for 1-2 years. For more in-depth information on seed saving, the University of Minnesota Extension offers an excellent guide.

Troubleshooting Common Issues

Even with the best instructions, gardening sometimes throws us a curveball. Here are a few common problems you might encounter and how to solve them.

Problem	Likely Cause	Easy Solution
My onion bulb only grew leaves, no flower stalk.	The bulb did not receive a long enough cold period (vernalization).	Ensure the bulb gets at least 4-8 weeks of cold temperatures (below 50°F / 10°C), either naturally outdoors or in the fridge before planting.
The flower stalk fell over before the seeds were ready.	This can be caused by strong winds or the weight of the seed head.	Support the stalk with a bamboo stake or a small plant support. As long as the stalk is not broken, the seeds will continue to mature.
The seed head looks moldy or rotted.	Too much moisture from rain or overhead watering.	Try to water at the base of the plant. If you expect a long period of rain as seeds are maturing, you can try to cover the head with a plastic bag with ventilation holes.
I collected the seeds, but they didn’t sprout next year.	Seeds were harvested too early or stored improperly.	Wait until the seed head is completely brown and dry on the plant before harvesting. Store seeds in a cool, dark, and dry location.

Frequently Asked Questions (FAQ)

1. Can I get seeds from an onion I bought at the grocery store?

You can try, but success isn’t guaranteed. Many store-bought onions are hybrids, meaning their seeds won’t grow true-to-type. They may also be treated with a sprout inhibitor to give them a longer shelf life. Your best bet is to use an organic, heirloom onion from a farmers’ market or one you grew yourself.

2. How many seeds will I get from one onion bulb?

You will be amazed! A single healthy onion flower head can produce anywhere from 500 to over 2,000 seeds. This is one of the biggest rewards of saving your own seeds—a little effort yields a huge return.

3. Do I need more than one onion plant to get seeds?

Onions can self-pollinate, so technically you can get seeds from just one plant. However, to maintain strong genetic diversity and get healthier seeds for future generations, it is highly recommended to plant at least a few onions of the same variety close together. This allows for cross-pollination between the plants, resulting in more robust seeds.

4. Why did my first-year onion (the one I grew for eating) send up a flower stalk?

This is called “bolting.” It happens when a young onion plant is stressed by unusual weather, like a sudden cold snap followed by warm weather. The plant gets confused and thinks it has already been through winter, so it prematurely starts its second-year mission of producing seeds. While you won’t get a good bulb for eating, you can let it flower and collect the seeds!

5. How long do onion seeds last in storage?

When stored properly in a cool, dark, and dry place, onion seeds typically remain viable for one to two years. Their germination rate will decrease over time, so it’s best to use them within that window for the best results.

6. What do I do with the original onion bulb after it flowers?

After the onion plant has put all its energy into producing a flower stalk and seeds, the original bulb will shrivel and become unusable. It has completed its life cycle. You can simply pull the whole plant up and add it to your compost pile after you have harvested the seed head.

Conclusion: Your Journey to a More Sustainable Garden

There you have it—the simple, proven way to get seeds from an onion bulb. By understanding its two-year life cycle and giving it the cold treatment it needs, you can easily unlock a continuous supply of seeds for your garden. It’s a process that saves you money, helps you grow stronger plants, and connects you more deeply to the food you grow.

I encourage you to give it a try. Pick out a beautiful onion this season and set it aside for your seed-saving adventure next spring. There is nothing more rewarding than planting a seed you collected with your own two hands. Happy gardening!