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How To Grow Bulb Onions In a Pot: Growth and Care Guide

If you are trying to grow bulb onions in a pot, you need to take the proper steps to ensure your onions are cared for to produce high-quality onions. Taking proper care of your bulb onions makes all the difference when it comes to maximizing bulb size and improving storage quality.

To grow healthy bulb onions, you need to plant your bulbs into a pot with loose, moist topsoil. Growing and caring for bulb onions requires an understanding of the onion variety you are growing, good soil quality, optimal temperatures, and effective nutrient management.

You might still be wondering how to grow and care for your bulb onions. No worries. Continue reading to learn more about the most important tips and strategies to grow your bulb onions in a pot with maximum growth and care. 

How Do You Grow Bulb Onions In a Pot?

Let us start with a brief overview of what you need to consider when growing bulb onions in a pot. Onions are shallow root, cold-season crops that are easier to grow due to their durability.

Depending on the quantity of onion sets you are growing, you may need a larger or smaller pot.  As a general rule, plant onion sets 2-3 inches deep into the potting soil and 1-2 inches apart. Given these measurements, you can get a good estimate of how large of a pot you will need. 

Once your bulbs start to grow, you can introduce dried leaves, fruit peelings, or other organic materials to the soil to improve moisture retention.

Here’s a quick video to show how growing onions in a pot can be easy, with more info below:

How To Promote Growth of Your Bulb Onions?

There are several variables that impact growth of bulb onions. When properly managed, these variables promote growth of your bulb onions.

Here are the most important variables you need to consider when growing bulb onions:

  • Onion Variety
  • Soil Quality
  • Climate
  • Pest Control
  • Nutrient management

Onion Variety 

Before you start planting your onions sets, you will need to choose an onion variety that matches the daylight hours of your region. These onion varieties reflect the amount of sunlight and time to maturity you can expect your bulb onions to need, not the type of onions you can see in the kitchen. (source)

We are going to look at the three main onion varieties.

  • Short-day onions: short-day onions grow well at latitudes of 25-35° and need 10-12 hours of daylight to start growing bulbs.
  • Intermediate day onions: intermediate day, also known as neutral-day, onions grow well at central latitudes of 32-42° and need 12-14 hours of daylight to start growing bulbs.
  • Long-day onions: long-day onions grow well at northern latitudes of 37-47° and need 14-16 hours of daylight to start growing bulbs.

Soil Quality

Like with other plants, soil quality is important for the development of your bulb onions. Onions thrive in well-drained, nitrogen-rich soil that contain high quantities of organic matter.

Some gardeners use well-rotted manure, while others prefer to use compost to increase organic matter. This organic matter is an important source of phosphorus and nitrogen, which is essential to bulb growth.

Additionally, you can use fertilizers rich in phosphorus to nurture bulb growth. You can carefully dig and place this fertilizer in between your bulb onions two to three weeks after planting. Make sure the fertilizer is close to the top soil so your onion roots can have easy access.

You should water your bulb onions soon afterward to ensure that the nutrients inside the fertilizer can be absorbed.


The climate of your region greatly influences your plant growth.

There are a few aspects of climate you need to pay attention to. Let us take a look at them.

  • Daylight hours: Generally, you want to choose an onion variety that matches the number of daylight hours in your region.
  • Temperature: With regards to temperature, onions grow better in colder temperatures and are considered frost-resistant vegetables. Onions thrive at temperatures ranging from 55° to 75°F but can tolerate temperatures above 75° if necessary.
  • Sunlight exposure: Even though onions can tolerate colder temperatures, they still need plenty of sunlight exposure. Place your pot where the sun can reach your bulb onions without shade from other plants. 
  • Precipitation Rates: If your region experiences higher rates of precipitation, then lower the quantity of water you give your bulb onions. The same idea applies to arid regions, except you would need to increase the water quantity instead. As a rule of thumb, always make sure the top soil is loose and moist so your onions can breathe and effectively absorb nutrient-rich water.

Nutrient Management

Poor nutrient management will deprive your bulb onions of nutrients and lower bulb quality. Onion lacking nutrients are more susceptible to rots and storage diseases.

There are three primary nutrients that play a key role in bulb growth:

  • Nitrogen: Although nitrogen helps maximize bulb size, too much nitrogen results in softer bulbs and increased vulnerability to storage diseases. Balancing nitrogen levels in bulb onions is important for improving bulb health without reducing storage quality.
  • Phosphorous: Helps with root development in the earlier weeks after the bulbs have been planted.
  • Calcium: Calcium is important for bulb density and fostering long-term storage quality. 

The most efficient way to deliver these three primary nutrients to your bulb onions is with fertilizer. You can apply fertilizer approximately three weeks after planting your bulbs. After the initial fertilizer application, you can continue by reapplying fertilizer every two to three weeks.

Here’s another video with tips on growing onions in containers:

Is it Hard to Grow Bulb Onions In a Pot?

Given all of these factors that go into growing bulb onions, you might be convinced that growing bulb onions in a pot is a difficult task. But compared to other vegetables, bulb onions are some of the most forgiving plants you can grow because of the vast range of temperatures they can handle. (source)

Even so, there are a few things to look out for to prevent any problems with your bulb onions:

  • Bolting: This is when an onion starts producing a flower stalk. Quick temperature fluctuations or extremely cold weather puts a lot of stress on your bulb onions. This stress induces your onions to start producing flower stalks in an attempt to survive and reproduce. The most effective way to prevent bolting is to keep the conditions of your bulb onions constant as possible.
  • Pest Control: Unless you are growing onions commercially, pests are generally not a problem. If you encounter any pest problems, you can cover your pot with a garden fleece to make a barrier between your bulb onions and pests.
  • Weeds: Like with other plants, weeds may be a potential problem as they steal water and nutrients from your onions. You can use a small weeding tool like this one to remove any weeds in your pot.

When to harvest Your Bulb Onions

If your onion tops start to fall over, this is a clear sign your onions are almost ready to be harvested. When you see this, make sure to stop watering and give the bulbs time to dry and harden.

Once the onions tops are completely dry, you can cut them from the bulb. Before storing your onion, lightly brush off any residual soil and store your onions in a cool, dry place.


At the end of the day, taking care of your bulb onions is essential for maximizing overall health and long-term storage quality. A deeper understanding of how to promote bulb onion growth and what problems to avoid helps guarantee that your bulb onions will flourish in any environment.

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