How to Grow Onions in Containers for Delicious Harvests Whenever You Want

You don't need a big garden to grow delicious onions at home—a bright location, the right container, and well-draining soil is all it takes to yield flavorful results. Whether you have a small balcony, patio, or windowsill, growing onions in pots and containers is an easy solution for gardeners with limited space. While this method is best suited for small-bulb varieties, such as bunching or pearl onions, it still yields an abundant harvest when done properly. Ahead, experts share their tips for growing onions in containers, from planting to harvesting.

Best Varieties to Grow in Containers

When growing onions in containers, our experts recommend choosing compact or fast-maturing varieties that thrive in limited space. "'Evergreen Bunching,' 'White Lisbon,' 'Red Baron,' and small bulb types like 'Paris Silverskin' or 'Pearl Onions' adapt well to container conditions and don’t require deep soil like large storage onions do," says Sara Rubens, certified garden coach and founder of Seed to Sanctuary.

Green onions (also known as scallions) work as cut-and-come-again container-grown onions. This means you can snip off some of the taller greens, leaving the rest of the plant in place, and it will keep producing green shoots, notes Luay Ghafari, author of Seed to Table. Like Rubens, he suggests not growing large-bulb onion varieties in containers. "You would end up only growing four or five in a 10-gallon pot," he says. "It's not economical when you factor in the cost of the soil."

How and When to Plant

Onions thrive in cool weather. Plant them in early spring, a few weeks before the last expected frost, or in late summer for a fall crop. "The easiest way to determine the best planting time is to check your local frost dates and count back eight to ten weeks if starting from seed," Rubens says. Alternatively, you can plant sets (small, immature bulbs) when temperatures are warm enough.

To plant onions in a container, Rubens suggests these steps:

1. Fill a small pot with high-quality, loose soil mix.
2. Moisten the soil slightly before planting.
3. Place seeds about one-quarter inch deep and one inch apart, or plant sets with the pointed end up, leaving the tip just visible above the soil.
4. Cover lightly with soil, pat down gently, and water thoroughly.
5. Keep the soil consistently moist until germination, which usually takes seven to 14 days. 

Choosing the Right Container

When selecting your container, pick one that is at least 10 to 12 inches deep to allow root growth. The container should also have a drainage hole to allow excess water to drain from the pot. "The width should accommodate the number of onions you want," says Rubens. "Remember, more width equals more onions." She adds that long, rectangular planters or wide, round pots work best for green onions.

Best Care Practices

Soil

Use a mix created specifically for container growing, which doesn’t compact and stays nice and airy all season long. Avoid heavy garden soil, which compacts easily and stifles bulb growth.

Sunlight

Make sure your container is placed somewhere that gets at least six hours of direct sunlight. Onions will do fine in partial shade, too, but will thrive in direct sun. 

Temperature

Onions grow best in cooler temperatures—between 55 to 75 degrees Fahrenheit—but will tolerate some heat if kept well watered. 

Fertilizer

Rubens suggests fertilizing onions every three to four weeks with a balanced liquid vegetable fertilizer and switching to a high-potassium feed once the bulbs begin to swell.

Watering

Onions require moist, but not soggy soil. Keep the soil evenly damp, watering when the top inch feels dry.

When and How to Harvest

How you harvest container-grown onions depends on the variety you grow. Ghafari recommends harvesting green onions by snipping what you need for a given recipe or dish you make. "Their cut-and-come-again nature makes it so that you will be able to harvest the greens all season long," he says. For varieties where you want to use the whole bulb, such as Paris Silverskin or Pearl Onions, harvest when the greens have started to fall over by gently pulling the bulb up from the soil.