Don’t let limited space keep you from enjoying delicious home-grown onions! No matter the size of your garden, we’ll show you how to produce a bountiful onion crop in containers all season long.
The first thing to consider when growing onions in a container is what kind of pot you’re going to use.
Onions have a fairly small root system, so just about any ole container you have lying around will do. But if you’re looking to get technical, a good rule of thumb is to aim for a container that is roughly 288 cubic inches (4,719 cubic centimetres) in size.
Depending on the size of the pot you’re using, you can also put multiple onion plants in one container. Growing multiple onions in one pot is a great way to increase yield while working with limited space. It’s typically suggested to space onion plants 1 - 2 feet (30 - 60 centimetres) away from each other. But for most varieties, you can get away with packing onions in a little tighter than this.
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Plastic pots, terracotta, and fabric grow bags all make fine containers for onions. When choosing a pot to plant onions in, the type of material it’s made out of doesn’t really matter. What does matter, however, is how well that material releases excess water.
Poor drainage is the number one killer of onions grown in pots. If your onions sit in standing water for too long, their roots will rot and the plants will likely wither away.
If you’re using a plastic container for growing onions, it’s crucial there are 2 - 4 holes in the bottom to allow excess water to drain.
Terracotta pots, along with fabric grow bags, are a great container option for onions because they are naturally porous. Most terracotta pots also come with a hole in the bottom for additional drainage.
If growing your onions in grow bags, be sure to test how well they drain before planting. If water doesn’t leak through the bag quickly, you may want to add one or two holes to the bottom to keep the roots of your onion plant healthy and happy.
Drainage also plays a key part in the type of soil you choose for onion containers.
Traditional soil, such as the type of dirt you can dig up in your backyard, is much too dense for onions planted in pots. It will trap moisture in the container to the point where it can cause fungal issues for onions as well as root rot.
Instead, opt for potting soil or soil specifically designated as safe for container gardening. Avoid all others.
Hopefully by now you’ve seen that growing onions in pots is pretty easy so long as you have the right container and right soil.
The key, as stated before, is drainage. You will likely notice that onions grown in containers are much thirstier than onions grown in a traditional garden bed. Be sure to adjust your schedule to water more frequently.
Of course, the same rules apply to container grown onions that apply to onions grown in a traditional garden, such as the amount of sunlight they need and when to plant them. You can find that information (and more!) in our complete guide on growing onions.