How To Grow Onions

Onions are an excellent vegetable to grow at home. They come in dozens of different varieties and are relatively easy to grow, even for the most green, but not green-thumbed, home gardener. They do well in containers or mixed into any garden bed. These growing instructions are general to any type of onion, so be sure to check your seed packet or with local grow experts for any particularities of the variety you choose to grow. Here’s how to grow onions:

Onions come in a huge range of shapes, sizes, colors and most importantly, taste. They can be generally divided amongst sweet onions and pungent onions. Red, white, yellow and Spanish cultivars are among the most popular types of onions. If you’re unsure where to begin, check with local growers to find out which varieties do best in your growing zone.

Onions do best if planted in cool temperatures, usually a few weeks before the last frost of the season. Onion tops will thrive in cold weather while the bulbs need warm temperatures to develop. Beware that most onions grown from seed take several months to mature. Alternatively, green onions are among the fastest to harvest.

Most types of onions will prefer full sun and need lots of light to thrive (14 – 16 hours per day). However, be sure to check the daylight requirement for you particular choice before planting. Short-day onions, such as “Red Hamburger” will form bulbs with only 10 – 12 hours of daylight. In hotter regions, some onions may prefer partial shade.

Onions can thrive in almost any type of soil but they tend to prefer loamy soil. The most important thing is to enrich the soil with lots of mature compost or an organic fertilizer before planting. Shoot for a neutral pH between 6.0 and 7.0.


Onions can be grown from seed, sets or transplants. Growing onions from seed will give you the most options as to which type of onion you’d like to grow. Transplants will give you a head start on the long growing process but may limit the types you have to choose from. Onions grown from sets are the quickest to harvest and tend to be less prone to disease. However, you will have the most limited cultivar choice when growing from sets.

When growing onions from seed, start them indoors about 6 to 8 weeks before the last frost of the winter. Growing onions from seed can take 4 months, so it is best to get a head start, particularly in shorter growing zones. Follow instructions on the seed packet for your particularly variety of onion but most onion seeds like to be sown about ½ inch deep and 1 inch apart. Water them regularly and provide lots of light once they germinate. Be sure to use fresh seeds each season as onion seeds are short lived.

Transplant 3 – 4 inch seedlings outdoors. Harden them off before leaving them outside overnight. Transplants can be planted outside as soon as the garden bed can be worked. Plant them 3 inches apart. Bury the stem up to where the leaves begin.


Plant onion sets pointy end up directly into your outside garden bed about 4 weeks before the last frost but be sure temperatures do not drop below 20° F. Cover them in about 1 inch of soil and space them about 5 inches apart.

Onions need 1 inch of water per week. Be sure to check the soil as onion plants often look healthy even when they need water. Transplants need more water than onion sets. If you use mulch, onions will not need as much water. However, they should be checked regularly and watered if need, particularly during hot, dry spells.

Most varieties of onions do not need much fertilizer if planted in an enriched soil. You may give them a few feedings throughout the growing season but avoid high nitrogen fertilizer, which makes for leafy plants at the expense of the bulbs.


Onion bulbs begin to ripen once the tops yellow and start to fall over. Once this happens, bend the tops down to hasten the ripening process. Loosen the soil. A day or two later, once the tops have turned brown, pull or dig up the onions bulbs. Leave them in the sun to dry. Handle them carefully to avoid bruising.


If you harvest the tops of certain cultivars of onions before the bulbs properly mature, you will have green onions (sometimes called scallions). Green onions have a milder taste than fully mature onion bulbs and are best when young and tender, about 6 to 8 inches tall. Cut them off about an inch above the bulb and you can replant the bulb.


Weed thoroughly. Onions do not compete well. Mulch will help prevent root competition.

When sowing seeds, try planting radish seeds with them. This will help mark the onion rows and lure maggots away form the onions.

Harvest onions in late summer before the weather becomes cool again.

Do you have tips on how to grow onions? Let us know in the comments section below!

Leave a Reply

Your email address will not be published. Required fields are marked *