Downsizing your garden? Moving to a smaller yard? Want to still enjoy home-grown onions? Growing onions in containers could be your answer! Container gardening differs from conventional gardening a bit. We have summarized and provided the essentials for growing onions in containers below.

Container selection and location

The most important factor is ensuring that your onions have enough room to grow. Onion containers must have at least 10″ of soil depth. The diameter can be any size as long as each onion has 3″ to 4″ of room to grow. You can use a 5 gallon bucket, planter box, or any sturdy container you may have. Be sure the container has good drainage holes and try to elevate it 1″ to 2″ off the ground.

Just like conventional onion growing, place your container where it will receive the maximum hours of direct sunlight. Onions grown indoors will require added day-length hours and heat units from artificial light; it may be easier for Mother Nature to handle the temperature curve.

growing onions in containers

Soil requirements for onions

Onions grown in containers will do best in well-draining, loamy soil with a slightly acidic pH. Be sure to enrich the soil with a balanced fertilizer or mature compost before planting.

Fertilizing your onion plants

At planting, spread 1 cup of a balanced fertilizer such as 10-20-10 Dixondale Farms Onion Special over a 10 sq. ft. area and incorporate in the soil. If using a weed and feed product, do not incorporate any deeper than 1″.

After 3 weeks to one month, feed your area with 1 cup of 21-0-0 Ammonium Sulfate or similar high nitrogen product and repeat every 3 weeks to 1 month until the onions start bulbing. Cut the fertilizer once you can tell the onions have started to bulb.

Planting your onions

Plant your plants 2″ apart in all directions to enjoy some green onions before your full size onions are mature. Green onions are ready to eat in as few as 4 weeks after planting by harvesting every other onion. All of the plant is edible, so don’t forget to use the tops, as well.

The remaining bulbs will then have enough room to make 4″ bulbs later in the season. Onions need about 4″ of space to grow to full size.  A 5 sq. ft. container, for example, will handle approximately 60 plants.

Watering onions in containers

The onions require approximately 1″ to 2″ of water per week. Be sure to check the soil as onion plants often look healthy even when they need water. If you use mulch, onions will not need as much water. However, they should be checked regularly and watered if needed, particularly during hot, dry spells. 

Check for moisture by inserting your finger in the soil. If you don’t feel moisture by your first knuckle, then it is time to water. We refer to this as “The Knuckle Rule”.

If you have further questions about your specific weather situation, give us a call at (830) 876-2430 or email