How to Grow Green Onions

Green onions and scallions make perfect additions for soups, potato pancakes, and, of course, all sorts of Asian dishes. They’re easy to grow, don’t take up a lot of garden space, and you can even regrow them from kitchen scraps.

What’s the Difference Between Green Onions and Scallions?

Before diving into how to grow green onions, let’s cover what it is and the difference to scallions. Both green onions and scallions are biennial plants belonging to the Allium family, which includes all onions, leeks, and garlic. Green onions (Allium cepa) are regular onions that have been harvested early, while scallions (Allium fistulosum) grow in clumps and have narrow bulbs. 

Scallions tend to be more tender and milder in flavor than green onions. They come in a wide range of varieties, from tasty Japanese Nabechan and bulbless Tokyo Long Whites to deep red Welsh onions and purple-bulbed Red Beards.

You may also see the term “spring onions” in the produce section. These are green onions that have been harvested while the bulbs are smaller in diameter.

You can use the same methods to grow all three types of onions. 

Growing Green Onions from Seed or Sets

How to Grow Green Onions from Seed or Sets

You can start green onions from seeds or by purchasing sets. Sets are dormant bulbs that you can get online or in local garden centers. You can plant sets the same way you do with flower bulbs like daffodils, tulips, and amaryllis. You’ll have a greater variety to choose from if you start with seeds, but you’ll save a little time if you begin with sets.

It helps to choose seeds or sets that work with your climate. Plant short-day green onions if the day length in your area is between 10-12 hours. Long-day varieties are well-suited for regions that receive 14-16 hours of sunlight, and intermediate-day onions thrive in almost any zone.

You’ll need to sow your seeds in a spot that gets at least six hours of sun with well-draining soil or in terra cotta pots. Make sure you label where you planted seeds, as scallions can easily be confused with garlic. Green onions are toxic for cats and dogs, so you may want to sow your seeds in places where your furry friends don’t usually hang out.

Green onions should be planted in the early spring to ensure a bountiful summer harvest. You can start green onion or scallion seeds indoors about 8-10 weeks before the last frost. If you’re sowing seeds directly in garden beds, wait until the soil warms up enough to work it easily. 

Green onions have tough roots, so you can sow several seeds in one area. When the seedlings reach about two inches tall, thin them to about three inches apart.

Keep the planted area moist, and the first green onion seedlings will emerge in 7-10 days. If you started your seeds indoors, move the seedlings to a sunny windowsill or keep them under a fluorescent grow light with a 16-on/8-off schedule.

Planting new crops in three-week intervals will provide you with continuous harvests.

Caring for Green Onions 

Green onions are relatively easy to care for as long as they get enough sun, and the moisture in the soil remains consistent. You don’t want the bulbs to dry out, but you also don’t want to flood the soil, or the roots may grow fungus and rot.

Adding mulch will help retain water and limit the number of weeds that will compete for much-needed nutrients. You can add small quantities of organic fertilizer every three weeks, but be careful not to overfertilize your green onions.

Managing Pests and Diseases

When it comes to plant health, be on the lookout for common diseases that affect green onions, including: 

  • Damping-off: If you notice that the roots rot shortly after the seedling emerges, your plants have succumbed to a fungus. You can reduce the chances of damping-off by thinning your seedlings, making sure the soil isn’t too drenched, and limiting the amount of fertilizer you use.
  • Onion Smut: This is a fungus that causes blisters near the base of the bulbs and streaks along the leaves. The best way to avoid onion smut is to rotate crops each season.
  • Downy mildew: This type of fungus produces gray patches on the leaves. You’ll want to avoid overcrowding and give your plants adequate air circulation to combat downy mildew.
  • Pink root rot: You’ll know you’re dealing with pink root rot when the roots start to turn pink to red. Eventually, the plants will turn brown, wither, and die. You can help avoid pink root rot by planting as early in the spring as possible.
  • Rust: This fungus causes rusty patches on stalks and leaves.
  • Insects: Green onions are susceptible to maggots, thrips, nematodes, cutworms, slugs, and allium leaf miners.

Gardeners can deter most pests and diseases by planting early in the spring, rotating crops, avoiding overcrowding, and giving green onions adequate sunlight and soil drainage. You’ll need to remove slugs by hand in the evening or create a barrier with coffee grounds or food-grade diatomaceous earth. Coating the leaves with an eco-friendly insecticidal soap is an effective way to discourage thrips.

Harvesting Green Onions

Green onions can reach up to three feet tall, but most people choose to harvest when they reach around 6-10 inches tall and about ¼ inch wide. You can cut pieces of the green stalks as the plant grows or pull the entire bulb out. Store harvested onions in a jar with roots in water or chop and freeze them.

Green onions and scallions can be harvested year-round in warm climates. You can overwinter your green onions by protecting them with a thick layer of mulch at the end of summer. If you plan to let your green onions grow as perennials, skip the first season’s harvest. This will allow the plant to become well established and increase the yield during subsequent years. The plant also blooms and produces seeds in the second season.

Propagating Green Onions

You can propagate green onions and scallions by division. First, dig up a bunch and gently pull them apart at the roots. Then, plant 1-3 individual bulbs in your garden bed or container with enough room to expand.

Regrowing Green Onions from Table Scraps

Besides knowing how to grow green onions, it’s also useful to learn how to regrow them. There’s nothing more convenient than having a continuous supply of your favorite vegetables and herbs. Regrowing green onions means you’ll always have them around to add to your favorite recipes. You’ll also save money in the process. 

Regrowing green onions is quick and easy. Here are the steps:

  1. Cut off the ends of the bulbs about one inch above the roots and rinse them under cool tap water.
  2. Place the onions with the roots down in a jar or glass of water.
  3. Set the glass on a sunny windowsill or porch, adding water when necessary. If the outer layer gets slimy, peel it off. You may also want to cut the roots down to an inch if they get too long and begin to bunch up.
  4. After a few days, you’ll notice that the roots have begun to grow. Change the water, and place the onions back in the jar.
  5. When they reach around five inches long, you can plant them in the garden or a medium-sized pot with nutrient-rich, organic potting soil. Plant several single onions two inches apart in the garden bed or container. Otherwise, you can keep them in water and harvest what you need right from your kitchen window.

Beginning gardeners can also buy bamboo kits to regrow onions. They’re easy to use and make a nice addition to kitchen decor.

Growing Green Onions Highlights:

ClimateWarm (68-78°F)
SoilSandy, rich, well-draining
Spacing2-3 feet apart
Seed depth¼ inch
pHAcidic to neutral (6.0-7.0)
Zomes (U.S.)6-9
Harvest60-80 days


Alice is a writer who grew up on a beautiful homestead in rural Old England. She now lives in New England with her fur babies and is on a mission to return to the land for a simpler, greener, and all-round kinder existence.

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