5 Key Points to Growing Onions in Containers

Onions can be grown just about anywhere under the correct conditions. This past spring, many turned to gardening as they had more time at home. Some may not have had the traditional amount of growing space once thought needed for growing onions, but still wanted to grow their own food. Growing vegetables in containers has gained popularity. If you are interested in growing onions in containers, there are a couple of key requirements that you should take note of.

Soil Requirements

Onion containers need at least 10 inches of soil depth. The diameter can be as large as you can accommodate. Customers have planted in plastic kiddy pools, 5 gallon buckets, flower pots, you name it. Here are a few examples.

Good drainage is key for any type of container. If you are using something plastic, just be sure to drill or cut holes in the bottom for the water to drain. Too much moisture in your onions can cause rotting and disease issues.

Container onions will do best in well-drained loamy soil with a slightly acidic to neutral pH. You can enrich your soil with a good, mature compost or balanced fertilizer before planting. Our recommendation for fertilizer is a 10-20-10.

Sunlight

You want to place your onion growing containers in a location where they will receive maximum hours of direct sunlight. We advise against growing indoors unless you will be using artificial light. Mother Nature does the best job of providing sunlight.

Onion Plant Spacing

For conventional growing, we recommend planting 4 inches apart for maximum bulb size. Due to a smaller growing area, we tell container growers to plant no closer than 3 inches apart. While you may get slightly smaller bulbs, you will be able to get more plants grown in a smaller area. For example, a 5 foot by 5 foot container will handle approximately 60 plants.

Green Onions

Also note that you can plant more plants initially and harvest every other plant for green onions. Be sure to harvest these green onions prior to the bulbing process to make sure the plants left in the container have enough room to bulb.

Water

Generally, onions require 1-2 inches of water each week. We use the “knuckle rule” to determine when it’s time to water. Stick your finger in the soil. If you don’t feel moisture up to your first knuckle, it’s time to water. Overwatering will cause the plant’s leaves to become translucent, so just be cautious of that.

Other than the key points listed above, treat your onions in containers just as onions should be treated conventionally. You can fertilize with a high source of nitrogen such as Ammonium Sulfate 21-0-0 in alkaline soils or Calcium Nitrate 15.5-0-0 in acidic soils. Stop fertilizing once you see bulbing start to take place. The tops will fall over once they are ready to be harvested.

As always, feel free to contact us with any more container onion growing questions! We want everyone to be able to grow and enjoy their onions.