How to Grow Onions in Your Garden (The Beginner’s Guide)

Ready to learn how to grow onions in your garden this season? Here’s everything you need to know.

Starting a garden or trying a new crop for the season can feel overwhelming and daunting, but it doesn’t have to be. Onions take up hardly any room, are super versatile, and last for months. A single 4 x 8 garden bed filled with them will last for months!

Interested? I’ve put together everything you need to know to start growing onions for your garden this year.

Why should you grow onions?

Onions are some of the most versatile vegetables to grow in your garden.

There are many onion varieties, yellow onion, red onion, white onion, sweet onion, pearl onion, shallots, scallions (green onions), and chives. Those are just the more commonly used onions for recipes.

They’re also an essential kitchen ingredient. Most recipes call for onions to add extra flavor. You might occasionally find yourself growing things in the garden you don’t really eat. But every cook can use onions. (Garden lettuce is another veggie that rarely goes to waste.)

Learning how to grow and harvest onions correctly can be a valuable garden skill.

Plus, they aren’t that difficult to store once you harvest them. Long-keeping varieties will keep up to a year!

Related: How to Grow a Money-Saving Vegetable Garden

What type of onion should I grow?

This is a great question with a surprisingly complex answer.

When growing anything, it’s always best to see what is suited for your climate and seasonal patterns. Growing onions is no different. In fact, it’s extremely important to pick the right onion for your latitude.

Onions are “programmed” to start bulbing up once the days reach a certain length in late spring and early summer. The farther north you are, the longer your days are in summer. Therefore, you would plant long-day varieties. Farther south, your longest summer day will be shorter, so you will plant intermediate or short-day varieties.

If you live in Georgia and June days are 13 hours long but you’ve planted a long-day onion that needs 14 hours to bulb, that onion will never bulb.

It’s important to understand that is not about temperature, but latitude.

Short-day onions form bulbs with 10-12 hours of sunlight. These tend to be very sweet, like the famous Vidalia onion.

Intermediate day (or day-neutral) onions form bulbs with 12-14 hours of daylight and produce beautiful onion bulbs in most regions. Candy, which comes in yellow and red varieties, is sweet, a good keeper, and perfect for intermediate-day regions.

Long-day onions form bulbs with 14-16 hours of sunlight and are better options for northern regions and colder climates. Copra (a great storage onion) and Walla Walla Sweet are good long-day onions.

🥕  You’d be amazed by how many onions you can grow in a smaller space. Check out these sample 10 x 10 garden plans and see how many you can fit in one row.

Do I need seeds?

There are three ways to start growing your own onions.

Planting transplants is when you have seedlings started in the current season and sold in bunches. This is my preferred method! My favorite source for onion plants is Dixondale Farms.

Onion sets are immature bulbs that were grown the previous year. Onion sets are typically what you might find at your local nursery.

Or you can use seeds, which take the longest amount of time to grow and tend to have the most issues. They need to be started in early winter, believe it or not.

When should I begin planting onions?

The best time to plant your onions when using transplants or sets is 4 to 6 weeks before the last frost. They go in early than just about anything else.

If you aren’t sure, check out this locator to determine what month is the best to plant onions in your area.

Step One: Prepare

Prepare the onion plants

Remove the onion sets from the box and keep them in a spot with plenty of cool air circulation until you can plant them. They often come in bunches that are wrapped in rubber bands. Be sure to cut the rubber bands to give them air.

If you can’t plant them right away, that’s okay! As long as they have air, they will be happy to wait for you up to a couple weeks.

Prepare the soil.

Choose a spot in your garden that receives plenty of direct sunlight. The soil should be crumbly and not compact; to loosen the soil up, work in compost. Onions love nitrogen, so if you have a high nitrogen fertilizer like composted chicken manure, that’s a great choice.

It’s also good to know what your soil’s pH is. Anything above 7.0 is alkaline, and anything below 7.0 is acidic.

Onions grow best in soil with a pH between 6.2 and 6.8. You can easily find a soil test kit at your local nursery or from Amazon.

step two: Plant

If you’re planting from onion sets, make planting holes 2 inches deep and 4 to 6 inches apart.

Place the set pointed end up and fill in the rest of the hole. Typically one pound of onion sets will plant a 50-foot-long row.

If you are planting transplants, only plant them one inch deep. Like sets, give them 4 to 6 inches in all directions.

If you’ve planted plants, they will look very small (almost invisible) in the garden. That’s okay! After a few weeks, they’ll green up and start growing quickly.

Step three: Caring for growing onions

Watering.

They need lots of water! Luckily they are planted in early to mid-spring, which is a rainy season in many parts of the country.

Onions have shallow roots, so keep an eye on the soil around the plants to prevent it from drying out and looking like it has cracks.

See some yellowing on the leaves? Decrease the amount of water you are giving the plants.

Always remember: The closer to harvest, the greater the amount of water that is needed.

But when the tops of the onions start falling over, stop watering and let the soil dry out before harvesting.

Fertilizing.

Remember, the best pH for onions is 6.2 to 6.8. Check your soil every few weeks.

If your soil becomes too acidic, use calcium nitrate to fertilize the soil to make it more alkaline. Use 1/2 cup per 10 feet of row.

If your soil is too alkaline, use ammonium sulfate.

Always water the onions after placing fertilizer and stop fertilizing when the onions start to form bulbs.

What is bulbing?

Bulbing is when the onion pushes the soil away, and the ground starts to crack. This is when you want to stop fertilizing.

How do I know when it’s time to harvest?

It’s time to harvest the onions when the tops turn brown or yellow and fall to the side.

How do I harvest my onions?

Harvesting onions is quite easy. You just them a good pull and the whole thing comes out. It’s very exciting and a great thing to do with the kids.

Pull the onions on a morning with plenty of sun in the forecast. You are going to dry the onions in the sun for two days.

You want to prevent sunscald, so place the tops of one row over the bulbs of another.

If it begins to rain, you need to bring the onions inside immediately. The moisture can cause rotting.

What happens next?

Once you have allowed the onions to dry out in the sun, you can place them in a cool location with decent ventilation, for example, a garage or porch, to continue drying out.

The leaves all the way to the bulb should be dry before you clip the roots of the onion at the bottom and cut the tops, too.

How do I store onions?

Dried bulbs will keep for around four months to a year in a mesh or net to permit airflow.

I use shallow cardboard boxes lined with newspaper so that the onions aren’t stacked too deep.

Check every so often for any soft onions to prevent the rest of the batch from spoiling. One bad onion can ruin a batch, so be diligent about this.

What do I need to look out for if there’s a problem?

First, know that onions are not a disease-prone crop! You are likely to breeze through the season without too much trouble. But if you are running into a problem, here are some possibilities.

My onions are turning yellow.

It could be poor soil causing your onions to turn yellow or also small onions.

Look at the spacing of your onions to make sure you gave the onions enough space. 4 to 6 inches apart is the best amount of space for your growing onions.

Remember to keep the soil loose and not tightly packed.

Lastly, check your soil’s pH and balance the soil to between 6.2 and 6.8 pH.

My onions are turning brown.

Fungus is typically the leading cause for onion leaves turning brown.

Other characteristics of fungal disease in onions are white onion rot, rusts, mold, smut, white leaves, and downy mildew. These could result from weather conditions being too hot and humid.

To remedy, try adding tomato feed, another high potash fertilizer, or even anti-fungal spray when you first see onions turning brown. This helps the soil with nutrient balance.

Unfortunately, if you notice any of the final diseases mentioned above, it’s typically too late to save the crop.

The best form of management is avoidance and sanitation.

My leaves are turning gray and wilting.

Your problem could be thrips.

Thrips are insects that can attack onion plants. They are hardly visible and appear as tiny yellow or dark specks.

Simply treat thrips with an application of insecticide.

How do I prevent fungus from attacking my crop?

It’s always best to prevent fungus from overtaking your onion crop before it becomes a problem.

The best prevention method is to ensure your plant spacing is the proper distance to help increase airflow.

Another preventative measure is using fungicide like Macozeb or Seacide every two weeks after planting.

One last tip!

Sweet onions don’t store as long as more pungent onions. So always use your sweet onions first!

Hope you enjoy this strange and fun veggie in your garden.