How To Grow Onions Indoors? – Can You Regrow Onion Bulbs?

You probably use onions every day in the kitchen. They’re crunchy, tangy, and incredibly versatile – all the more reason to grow your onion garden! Many gardeners with small growing spaces, or without any, believe this isn’t the vegetable for them since they take a lot of room to grow.

But, the truth is, you don’t need an extensive vegetable garden to grow onions. You can easily grow them in containers on your patio or balcony or have them as a houseplant on your windowsill! It’s not only practical but super easy too! The easy-going plant adapts well to your indoor space, giving beautiful green, erect foliage to add freshness to the environment.

Just read the post, and you’ll learn how to grow onions indoors, plus everything else that is essential to get you started on your indoor onion garden.

What Kind Of Plant Onion Is?

One of the most commonly cultivated vegetables, the onion, belongs to the Allium family of plants. Famous for their characteristic intense flavor, they’re used in countless recipes worldwide. Onions don’t just bring a sharp, spicy flavor to dishes; they also provide bundles of health benefits.

What Are The Health Benefits Of Eating Onions?

For example, they’re a good source of fibers, Vitamin C, and folic acid. Regular consumption of onions can reduce the risks of many types of cancers, lower your blood pressure, improve skin health, and maintain healthy hair.

With over a million uses, onion is one of the most versatile vegetables you’ll find. And it’s not just the bulbs that you can grow them for. With an indoor onion plant, you receive an endless supply of fresh green tops to garnish your soups, stews, and curries, or add them to sandwiches, stir-fries, bread, or pancakes.

So, How To Grow Onions Indoors?

Whether you’re regrowing onion bulbs or starting from scratch with seeds, the technique is pretty straightforward. You might not get a big harvest when your growing onions indoors in pots, but the onion tops offer fresh, flavorful addition to several everyday recipes.

If you’re growing onions for the first time, follow the recommended method below for guaranteed success.

Here’s How To Grow Onion Indoors In A Container

You’ll need a 6 to 10 inches (about 15 to 25 cm) deep container to grow onions, depending on the variety. A 10-inches (about 25 cm) depth allows plenty of room for bulb development. If you’re only growing them for the tops, you can even plant them in a plastic bottle or a paper cup to harvest the shoots as they come along. You can use a plastic tub, a bucket, or a standard gardening pot for many onion plants. For example, in a 5-gallon (about 19 liters) bucket, you can grow 3 to 5 onions.

Don’t Forget The Drainage Holes!

Ensure that the container has drainage holes at the bottom before filling it up with well-draining potting soil (halfway if you’ll regrow onion bulbs, and to the top, if you’ll sow onion seeds). You can also sprinkle some 10-10-10 slow-release fertilizer over the potting soil and mix it in.

Seeds, Bulbs Or Store Bought, It’s A Matter Of Choice

If you’re planting seeds, sprinkle them over the surface and push them ¼ inch (about 0,5 cm) deep into the soil. If you’re regrowing onion bulbs, plant the sets one inch (approximately 2,5 cm) deep, closely packed if you’ll only harvest the greens, but at least 2 inches (about 5 cm) apart if you’ll gather the bulbs when they’re mature.

You can also grow them from store-bought green onions, with the stalks removed. Additionally, the onion bottoms with the roots you discard after using onion in your dishes can also be planted to give it a new life.

Remember To Water

Spray water over the soil until it’s moist, and place the container at a sunny location, preferably a south-facing window. You can start harvesting the green tops once they’re 6 inches (about 15 cm) tall. Leave a bit of stalk attached each time you cut the greens, and it will regrow again.

How To Grow Onions In Water?

Onion is a hardy plant. It will grow no matter how you treat it. Believe me or not, a popular technique for indoor onions is to grow them in the water!

You’ll need a bottle or a jar that’s just wide enough to hold the onion bulb on the top. Add enough water that the onion bottom, with the roots, is submerged. Place it in a sunny spot, watch it grow, and start harvesting fresh greens in just a couple of weeks. If necessary, add more water to keep the roots submerged. As simple as that!

What Are The Best Conditions For Growing Onions?

Now that you understand the basics, here are some specific growing conditions that your indoor onion plant will need to continue thriving:

Do Onions Need A Lot Of Sunlight To Grow?

One of the primary considerations when growing onions as houseplants are to provide them with ample light. They’ll need about 10 to 16 hours of sunlight to form a bulb at the right time, depending on the type. While they’ll have adequate light sitting next to a sunny window in the warmer months, the fall and winter months will need supplemental lighting.

In the cooler months, when there isn’t enough light for your indoor plants, place the onions under grow lights, leaving them on for a couple of hours every day to mimic the outdoor conditions.

How Much Water Onions Need?

When you grow onions indoors and do that in containers, they will need around 2 to 3 inches (about 5 to 7,5 cm) of water each week. Check the plants daily by touching the topsoil and see if it’s dry. Water the plants when the topsoil is dry to touch.

Should You Fertilize Your Onions?

Once your onions are up and growing, start feeding them twice a month with a water-soluble 15-30-15 fertilizer applied at half the strength that’s mentioned on the package.

What Onion Types Are Excellent For Indoor Growing?

Almost all indoor gardeners start onions from store-bought onions or scallions, regardless of the variety. And it’s a great idea too since it’s convenient, effective and fast! You can also buy onion sets from the nursery (small, dry onions from the previous season’s harvest).

But, with these options, you’ll not have many varieties to choose from. Instead, if you want to try some unique types that aren’t otherwise available, try growing from seeds. Here are some of the varieties you can grow indoors:

1. Crystal White Wax

These are scallions with fresh, tender stalks and small round bulbs, ready for harvest in just about 95 days.

2. Evergreen Long White

This compact variety is perfect for indoor growing, with thin, long stems and small white bulbs at the bottom. They’re ready for harvest in 65 days.

3. Red Burgandy

This variety is perfect for growing mature bulbs, 3 to 4 inches (about 7,5 to 10 cm) wide with dark red skins. It’s an heirloom with a sweet flavor, best eaten fresh. Since it’s a short-day onion, it will need 10-12 hours of light for bulb formation.

4. White Sweet Spanish

This compact onion reaches maturity in 110 days, with small white bulbs perfect for salads and fresh green stalks, perfect for garnish.

5. Sturon

This is a long-day, high-yielding onion, ready for harvest in 80 to 100 days. It will need 14 to 16 hours of light per day and form medium-sized round bulbs with brown skin and yellow flesh.

What Mistakes To Avoid When You’re Growing Onions Indoors?

Before you start growing onions indoors, there are some things you need to keep in mind. Here are some of the things you’ll need to avoid:

  1. Avoid watering once the foliage begins to die. Near harvest, the bulbs will need less water to prevent them from rotting.
  2. When the bulbing starts, bulbs will push out of the soil; don’t replace the dirt over them. They will need to emerge from the surface for proper development.
  3. Stop fertilizing once the bulbing starts and onions emerge from the soil.
  4. Don’t let the soil dry out, especially during the summer months. Dry soil can turn the onions bitter.
  5. When planting the next batch of onions, please don’t use the old potting soil unless you’ve refreshed it with some compost or fertilizer.

How To Grow Onions Indoors? – In A Sealed Package

Temp Required55 To 75°F (About 12,5 To 24°C)
Sowing TimeAll Year, But Preferably Spring And Fall
Type Of SoilWell-draining, Loose
Transplanting Time6 Weeks After Planting The Seeds
Harvesting Time100 To 120 Days, Depending On The Variety
Light DurationShort-day (10 – 12 Hrs), Intermediate-day (12 – 14 Hrs), Long-day (14 – 16 Hrs)
Watering2 To 3 Inches (From 5 To 7,5 cm) Per Week For Container-grown Onions
FertilizationDiluted 15-30-15 Fertilizer Twice A Month

Final Words

Hopefully, you now know how to grow onions indoors, and remember that even though you might not get many bulbs with an indoor garden, but an endless supply of fresh greens is a guarantee!

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