How to Grow Onions (Quick and Easy Growing Tips)

Onions aren’t the fastest-growing thing you can plant, but I would say they’re definitely worth the wait. 

They do not mind if you forget to water them sometimes, and they do not need anything special to grow. 

Just give them good soil, enough sunlight, and a little patience. 

Once you grow your own, you will probably want to keep doing it because fresh onions always feel nice to have (not to mention they are useful in the kitchen). 

If you’re also interested in other easy-to-grow vegetables, check out how to grow zucchinis, potatoes, eggplants, and cucumbers.

Quick Onion Overview

Category	Details
Scientific Name	Allium cepa
Family	Amaryllidaceae
Genus	Allium
Type	Biennial (grown as an annual)
Soil Type	Well-draining, loamy soil
Soil pH	6.0 – 6.8
Habitat	Native to Central Asia, cultivated worldwide
Common Pests	Onion maggots, thrips
Common Diseases	Downy mildew, onion rot

Choosing the Right Onion Variety

Not all onions grow the same way, so it helps to pick the right type for where you live.

There are short-day, long-day, and day-neutral onions, and the one you choose depends on how much sunlight your area gets.

Short-Day Onions

Short-day onions start forming bulbs when daylight lasts around 10 to 12 hours. They are best for warmer climates, specifically USDA zones 7 to 10, where winters are mild and summers do not get too long.

These onions grow well when planted in fall or winter, giving them time to mature before the heat of summer.

Some short-day varieties include:

• Texas 1015Y
• Granex 33
• Yellow Granex
• White Bermuda
• Red Burgundy
• Crystal White Wax
• Texas Early Grano 502
• Sweet Red
• Red Creole
• Texas Super Sweet
• Georgia Sweet
• Early Grano
• Southern Belle Red
• Candy Apple Red
• White Grano

Long-Day Onions

Long-day onions need around 14 to 16 hours of sunlight to form bulbs, making them ideal for cooler northern climates, typically USDA zones 3 to 6.

These onions should be planted in early spring so they can take advantage of the long summer days.

They tend to grow larger and store better than short-day onions.

Some common long-day varieties include: 

• Walla Walla
• Yellow Sweet Spanish
• Copra
• Patterson
• Highlander
• Blanco Duro
• Bridger
• Ringmaster
• Sterling
• White Sweet Spanish
• Gladstone
• Redwing
• Red Zeppelin
• Red Wethersfield
• Red Florence

Day-Neutral Onions

Day-neutral onions (also called intermediate-day onions) do not rely as much on daylight length and will form bulbs with about 12 to 14 hours of sunlight.

This makes them a great choice for gardeners in zones 5 to 7 or for those unsure of which type to plant.

They can be grown in both northern and southern regions with decent results.

Some good day-neutral varieties include: 

• Candy
• Super Star
• Expression
• Sierra Blanca
• Cabernet
• Super Star (All-America Selections Winner)
• White Bermuda
• Sierra Blanca (also comes in yellow)
• Red Candy Apple
• Monastrell
• Red Stockton

If you are not sure which variety is best for your area, checking a local planting guide or asking at a nearby garden center can help.

When to Plant Onions

When growing onions, timing matters because they need the right amount of daylight to grow properly.

In warmer climates, like USDA zones 8 to 10, onions should be planted in late fall or early winter, around October to January. This way, they can grow during the cooler months and be ready for harvest by spring.

In colder areas, such as zones 3 to 7, onions should be planted in early spring, as soon as the soil is workable (usually between March and April).

The goal is to give them enough time to grow before the summer heat arrives.

If you are starting onions from seeds, plant them indoors about eight to ten weeks before the last expected frost in your area.

For most places, this means starting them indoors in January or February so they are ready for transplanting in March or April.

If you are using onion sets or transplants, plant them directly in the garden once the risk of a hard frost has passed but while temperatures are still cool. In most regions, this is around late March to May.

Seeds, Sets, or Transplants?

Onions can be grown from seeds, sets, or transplants, and each has its own pros and cons.

Seeds

Growing onions from seeds gives you the most variety since you can choose from a wide range of types, including rare or heirloom varieties that may not be available as sets or transplants.

The downside is that they take the longest to grow and require more attention in the early stages.

If you start seeds indoors, you will need about eight to ten weeks before they are strong enough to go outside.

This means planting them in trays or containers with good soil in January or February (if you live in a colder climate) so they will be ready for transplanting in early spring.

If you prefer a quicker option, you can also try direct sowing seeds outside once the weather is warm enough.

It is a bit of a waiting game, but if you want more control over the type of onions you grow, seeds are worth it.

Sets

Onion sets are small onion bulbs that have already started growing from the previous season. They're one of the easiest ways to grow onions because they sprout quickly and need less care than starting from seeds.

Since they're already partially grown, they can handle cooler weather and be planted earlier in the season.

The downside is that sets don't usually grow the biggest onions, and you’ll mostly find basic varieties like yellow, red, or white onions. But if you're looking for something easy and dependable, sets are a solid choice.

Transplants

Onion transplants (also called onion starts) are young onion plants that have already been grown from seed and are ready to be planted directly into the garden.

They are a good middle-ground option if you do not want to start from scratch with seeds but still want decent-sized onions.

Transplants establish themselves quickly and usually produce larger onions than sets. For the best results, make sure to follow proper care tips, like how to water transplants, to help them thrive.

The main downside is that they can be a bit more expensive than seeds or sets, especially if you are buying a lot of them.

But if you are looking for an easier way to grow onions without waiting months for seedlings to develop, transplants are a good choice.

Each has its advantages, so it really comes down to what works best for you.

• If you like variety and do not mind the extra time, go with seeds.
• If you want something fast and easy, sets are the way to go.
• And if you are looking for a balance between the two, transplants might be your best option.

Preparing the Soil

Onions love well-draining soil that’s rich in organic matter. They don’t do well in compacted or rocky soil, so if yours isn’t great, mixing in compost or aged manure helps a lot.

If you’re interested in making your own compost, the Berkeley method composting is a fast and effective option.

The soil should be loose, light, and slightly acidic to neutral (somewhere between 6.0 and 6.8 on the pH scale).

If your soil holds too much water, adding sand can improve drainage. Using natural fertilizers can also help enrich your soil without harming the environment. If you’re unsure about your soil’s pH, testing it can save you some trouble later.

Quick Guide on How to Plant Onions

1. Pick a sunny spot because onions love sunlight and will not grow well in the shade. They like to soak up as much light as possible to develop those nice, plump bulbs.

2. Loosen the soil at least 8-10 inches deep and mix in compost or well-rotted manure (onions like a soft bed to stretch their roots in).

3. If planting seeds, sow them about half an inch deep, cover lightly with soil, and keep them moist.

4. If using sets, push them into the soil just enough so the tip is barely sticking out.

5. If planting transplants, bury the roots while keeping the green tops above the soil.

6. Space onions 4-6 inches apart for big bulbs (if you’re growing them for green onions, you can plant them closer together).

7. Once they are in the ground, all you need to do is keep an eye on them, water when needed, and let them do their thing.

Taking Care of Your Onions

Onions like steady moisture but don’t want to be drowning (they’re a bit picky that way). 

Water them regularly, especially during hot weather. A good rule of thumb is to make sure they get about 1 inch of water per week, either from rain or watering.

They also don’t compete well with weeds. Since onions have shallow roots, weeds can easily steal their nutrients. 

Keeping the area weed-free (or using mulch to block weed growth) helps them grow better. 

A little fertilizer now and then doesn’t hurt either, especially one that has more nitrogen early on to help with leaf growth.

Dealing with Pests and Diseases

Onions don’t get a lot of problems, but when they do, it’s usually pests or diseases.

Onion maggots

These little pests feed on the roots and bulbs, causing onions to rot. To prevent them, avoid planting onions in the same spot every year and cover young plants with fine mesh netting.

Thrips

These tiny bugs suck the juices from onion leaves, causing them to turn silvery and curl. A strong spray of water or insecticidal soap can help control them.

Fungal diseases

If you live in a humid area, watch out for fungal problems like downy mildew or onion rot. To avoid these, space your onions properly for good airflow and avoid overwatering.

Harvesting and Curing

You’ll know your onions are ready when the tops start falling over on their own. At that point, stop watering them and let them sit for a few days before pulling them up.

Once harvested, onions need to be cured (which is just a fancy way of saying they need to dry out) so they store well.

Spread them out in a warm, dry place for two to three weeks until the outer skins feel dry and papery.

If the weather is nice, you can cure them outside in a shaded area with good airflow. If it’s too damp, curing them indoors works too.

Storing Onions

Once cured, onions should be stored in a cool, dry place with good air circulation. 

Keeping them in mesh bags or baskets works better than sealing them in something airtight (unless you enjoy finding moldy onions later). 

Avoid storing them near potatoes, since potatoes release moisture that can make onions go bad faster. If stored properly, they can last for several months.

Companion Planting for Onions

Onions do not mind sharing space, but they grow better next to certain plants. 

Some help keep bugs away or leave enough room for onions to grow, while others steal nutrients and slow them down. 

So, I have listed some good plants to grow with onions and a few you should keep apart.

• Good companions: Carrots, lettuce, beets, chamomile, and tomatoes all help onions thrive (some of these even help keep pests away).
• Plants to avoid: Beans, peas, and asparagus don’t get along with onions. They can slow down onion growth and compete for nutrients.

I hope this guide helps you get started with growing onions! 

Have you grown them before or have any tips to share? Drop them in the comments!

Happy growing!

Frequently Asked Questions (FAQs)