Spring Onion vs. Leek: Understanding the Differences

Written by Nikita Ross
Updated: August 8, 2023
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Spring onions, scallions, green onions, leeks — there’s a lot of confusion about the similarities and differences. While these plants are all related, there are notable differences in growing habits and flavor profiles.

The term “spring onion” is often used for several different species in the onion family, creating additional confusion for gardeners and culinary creators. Here are the key differences between spring onions and leeks so you know how to grow and use these delicious plants.

Spring onions have a stronger onion flavor than leeks.

Comparing Spring Onion vs. Leek

Spring OnionLeek
ClassificationAllium fistulosum, Allium cepaAllium ampeloprasum (Allium porrum)
Alternative NamesWelsh onion, Japanese bunching onion, scallionsOften mistakenly called scallions.
OriginAsiaEurope, Asia
DescriptionVertical stalks with a rounded, white end and root base growing into deepening green, broad leaves at the top. It grows up to 3 feet tall and spans from 1-2 inches at the base to 6-12 inches in span at the top.They are used for culinary purposes.
UsesUsed for culinary purposes.They are used for culinary purposes, often as a base for soups and stocks or as an accent in sauces and stir-fry.
Growth TipsPlant directly into well-draining soil in USDA Zones 5-10 after the risk of frost has passed. Plant in full sunlight and water weekly, keeping the dirt moist. Harvest when the stalk reaches 6-12 inches high. Consider planting every few weeks for a continuous supply.Start seeds indoors 12 weeks before the last frost in USDA Zones 5-9. Transplant to well-draining, acidic soil in full sunlight. Weed control is essential, as leeks have minimal resistance. Cover initial growth with dirt to the top of the stalk. Water weekly or more in dry areas, using mulch to trap moisture. Harvest when the width exceeds an inch, and the stalk is sturdy.
Interesting FeaturesThe term “spring onion” is used interchangeably with regional variances, leading to mass confusion over what a spring onion really is.High in vitamins A and K. Toxic to cats and dogs.
Flavor ProfileSweet, mild, peppery, moderate onion flavorMild, sweet, subtle onion flavor

What Are the Key Differences Between a Spring Onion and a Leek?

Even when mislabeled, spring onion and leeks are scientifically different species in the onion family. The confusion comes from the use of the word “scallions” as a blanket term for both plants.

Spring onions have a small, white bulb at the end, while leeks typically have a rounded, bulb-free root base. Although the coloration and growing patterns are similar, the greenery of spring onions tends to be softer and tubular, whereas leeks sprout into broad, thick leaves.

Spring onions have a stronger onion flavor than leeks, though it’s still milder than a full-grown onion. Leeks are quite mild with a subtle, sweet flavor.

Spring Onion vs. Leek: Classification

Spring onions are often classified as Allium fistulosum or Allium cepa — two different species of onion. This is where the confusion about what spring onions really stem from.

Allium fistulosum is the Welsh onion. Allium cepa is the common onion. They are similar in taste, appearance, and growing habits. The key difference is in the bulb. Allium fistulosum doesn’t have a large bulb at the end like Allium cepa and looks more like a leek in that regard. Spring onions can be either Allium fistulosum or Allium cepa as long as they’re harvested before full maturation.

Leeks are also members of the Allium (onion) family, though it’s a unique species with several varieties and cultivars. When added to dishes, leeks are often mislabeled as scallions due to their similar appearance and flavor profile.

Spring Onion vs. Leek: Origin

Spring onions of both the Welsh onion and common onion variety originate from Asia. The name “Welsh” onion is another misnomer that confuses this issue. “Welsh” is an Old English term for someone foreign or unknown. The use of onions for cooking and remedies dates back thousands of years, with traces of onion discovered at Bronze Age sites. The history of when people started harvesting them early as spring onions is unknown.

The use of leeks also dates back to Biblical times, with records of their consumption as far back as ancient Egypt. Leeks have also long been a symbol of Wales, with Queen Elizabeth II’s coronation gown, alongside the Irish shamrock and Canadian maple leaf.

Asia is where spring onions originate from.

©iStock.com/chengyuzheng

Spring Onion vs. Leek: Description

Spring onions have small, white bulbs at the base, which are less pronounced in Welsh onion varieties. These bulbs grow in slender, vertical stalks with a deepening green shade toward the top. Stalks are 1/4 – 1/2 inches in diameter, tubular, and hollow with soft foliage. A spring onion will grow 2-3 feet tall and mature into a full onion if left unharvested. As such, they should be harvested at 6-12 inches before maturation.

Leeks have a rounded white end, similar to a Welsh onion. They grow in vertical stalks in deepening green toward the top, where the stem separates into broad, gritty leaves. Leeks grow up to 3 feet tall, 1-2 inches thick at the base, and have a 6-12 inch span at the top.

While spring onions are smaller than leeks, their flavor packs a punch. While still milder than a mature onion, spring onions have a peppery, sweet onion flavor. The intensity varies based on watering habits and the harvest period.

Leeks are milder and sweet with a subtle onion flavor. The delicate flavor and aroma make leeks a favored substitute for onions in cooking.

Spring Onion vs. Leek: Uses

Both spring onions and leeks are primarily used for cooking. Both share a similar flavor profile and uses, though spring onions tend to be an accent flavor, and leeks tend to be a base.

Spring onions are a flavorful addition to stir-fries, salads, and meat dishes. Leeks are commonly used in soups and sauces for a subtle pop of flavor.

Leeks cut into pieces for cooking

Leeks are commonly used in soups and sauces.

©iStock.com/ArtCookStudio

Spring Onion vs. Leek: Growth Tips

To grow spring onions, start seeds directly in well-draining soil in full sun after the risk of frost has passed. Onions thrive in USDA Zones 5-10. Water weekly, keeping the dirt moist, but avoid overwatering to maintain the flavor. Harvest when the stalk reaches 6-12 inches high, usually around eight weeks into the growth cycle. Consider planting every four weeks for a continuous supply.

To grow leeks, start seeds indoors 12 weeks before the last frost in USDA Zones 5-9. If you live in zone 7-9, you can also plant leeks in the fall and harvest in the spring with garlic. Pretreat and weed the soil to remove any potential infiltrators, as leeks lack weed-resistant properties. Transplant the sprouts to well-draining, acidic soil in full sunlight after the risk of frost has passed. Cover the sprouts in the dirt to the top of the stalk. Water weekly or more in dry areas, using mulch to trap moisture. Harvest when the width exceeds an inch, and the stalk is sturdy — usually in the fall.

The photo featured at the top of this post is © Graham Corney/Shutterstock.com


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About the Author

Nikita Ross is a writer at A-Z Animals primarily covering plants, gardening, and yard care. Nikita has been writing for over seven years and holds a Marketing diploma from NSCC, which she earned in 2010. A resident of Canada, Nikita enjoys reading in her library, epic beach naps, and waiting for her Coffea arabica plant to produce coffee beans (no luck yet).

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