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.
Comparing Spring Onion vs. Leek
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 are stems 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. Leeks are often mislabeled as scallions due to their similar appearance and flavor profile when added to dishes.
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 adding confusion to 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.
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 inch 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.
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.
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