Growing Onions in Containers

Last Updated on October 1, 2022 by Ellen Christian

These tips for growing onions in containers will answer all your questions! Learn how to grow onions in pots and enjoy a bountiful harvest.

Growing Onions in Containers

Onions are one of the most versatile vegetables because they can be used in so many different ways. If you’re interested in being able to grow your own food, onions are one of the easiest vegetables to start with.

While many gardeners grow onions in a traditional garden or raised garden bed, you can easily start growing onions in containers if you don’t have as much room.

Growing onions is really quite simple. This year, I’m planting the red onions and Stuttgarter Yellow onions I got from Nature Hills Nursery.

You can find all sorts of bulbs including flower bulbs and garlic bulbs. But, that’s not all. Nature Hills Nursery has flowering trees, lilac bushes, fruit trees, roses, and perennials. 

How do you grow onions?

There are several different ways you can grow onion plants. You will need to plant your onion plants in early spring. This will allow you enough time to harvest your own onions.

• Onion seeds – You will need a very long growing season and to start this inside to get them to mature in time. I find it easier to plant onions directly outside rather than grow onions indoors.
• Onion sets – These are tiny onions that you plant and allow to grow to full-size onions. A set looks like a small onion bulb.
• Onion seedlings – You can purchase onion seedlings from some nurseries if you don’t feel you have enough time to grow them to maturity. Just plant your onion plant when you put in the rest of your garden.

I find it easiest to grow onions from sets. This allows the plants to mature in my growing season.

Do onions grow well in pots?

Onions do very well in pots. I’ve had great success growing onions in different-sized containers. How many you can fit in a bucket will depend on whether you want them to grow to full-sized onions or plan on harvesting them as green onions.

It’s important when you grow container onions that you add well-rotted manure to your potting mix. This will help you harvest healthy onions.

If you want a decent crop when you grow onions in containers make sure you give each onion enough growing space.

What type of soil do onions need?

Onions prefer rich, loamy soil that is high in organic matter. You can amend your potting mix with compost to provide the nutrients onions need to grow well.

You’ll have the best luck growing onions in containers with rich, healthy soil.

Green onions or onion bulbs?

Because we container garden, we plant onions for the green onions on top. We don’t expect the onion bulbs to get that large.

Onion plant spacing

For green onions, you need to space your onion plants about 3 inches apart. Be sure to allow sufficient space to let the onions form.

For larger onions that you plan on harvesting the bulbs, give each onion at least 6 inches of space.

When we plant the sets, we plant them relatively close together. After a few weeks, we will see green onion shoots sprouting up. We snip these off through late fall and use them when we cook.

Sunlight requirements for onion plants

Onion plants like full sun but will tolerate some shade. I have found they do better with at least 6 hours of sunlight each day.

Watering requirements for onion plants

Onion plants need to be kept moist but not wet. Allow the soil to dry out a bit between watering. During the hot weather, you may need to water your onions every day.

How often do you need to fertilize onion plants?

I like to add some compost to my container gardens every few weeks. This helps keep the nutrients up and ensures I have a good harvest.

Check out the selection at Nature Hills Nursery.

Do onions need full sun?

Onions prefer full sun but will tolerate partial shade. If you live in an area with very hot summers, providing some afternoon shade will help prevent your onions.

When growing onions in containers, sun is very important.

Planting time for onions in pots

When to plant your onions will depend on the type of onion you’re growing and your climate.

Onion sets can be planted as soon as the soil can be worked in the spring.

Onion seedlings should be planted after all danger of frost has passed.

How to Plant Onion Sets in Pots

Fill your large pots with a high-quality potting soil mix with a thin layer of organic matter.

Loosen the soil in the pot and make a small hole for each onion set.

Place the onion sets in the holes, making sure the root side is down.

Fill in around the onion sets, gently pressing the soil to remove any air pockets.

Water well.

Why is my soil waterlogged?

When growing onions in pots, it’s important the pots have drainage holes. This will allow the water to escape through the holes.

Growing onions from seeds

Onions grown from seed will need to be started indoors 8-10 weeks before your last frost date.

Fill your pots with a high-quality potting soil mix and place them in a sunny location.

Sow the onion seeds thinly on the surface of the soil and lightly press them into the soil.

Water well and keep the soil moist.

When the seedlings are 4-6 inches tall, thin them so they are about 4 inches apart.

Transplant the seedlings into larger pots or into your garden when they are 6-8 inches tall and the danger of frost has passed.

Caring for Onion Plants

Once your plants are in the ground or pots, there are a few things you need to do to make sure they have everything they need to grow well.

Fertilize your onions every 2-3 weeks with a water-soluble fertilizer.

Water regularly, as onions need 1-2 inches of water per week. Try to avoid uneven watering.

Weed around your onions to prevent competition for resources.

When should you harvest your onions?

Onions are typically ready to harvest about 110 days after planting. Keep an eye on your plants and when the tops start to yellow, it’s time to dig them

Harvesting Onions

Now that you’re done growing onions in containers, it’s time to harvest them.

Onions are ready to harvest when the onion tops begin to yellow and fall over.

I harvest them before the mature flower stalks grow flowers.

Cut the tops off the onions, leaving about 1-2 inches of stem.

Allow the onions to cure in a sunny location for a week or so. The summer heat will help dry them out.

Cured onions can be stored in a cool, dark location for several months.

How to store onions

Onions can be stored in a cool, dark location for several months.

The best way to store them is in a mesh bag or wire basket.

This will allow air to circulate around the onions and prevent them from rotting.

Check on your onions every few weeks and remove any that are beginning to rot.

Onions are one of the easiest vegetables you can grow in pots, so if you’re short on space, don’t let that stop you from enjoying fresh onions from your own garden. With just a little care, you can have a bountiful harvest of these versatile vegetables.

Now that you know how to grow onions in containers, check out a few of these posts. These tips should also work just as well for growing garlic in pots. Check out the selection at Nature Hills Nursery.

• Container gardening ideas for vegetables
• How to grow peas in a pot
• Best plants for self watering pots
• Cut roses care
• Are lilac flowers edible
• Full sun flowers