There are a ridiculous number of onion varieties, so choosing the right onion can make my head spin sometimes. With four distinct types of "green onions" that all look almost the same, I'm guessing you have the same issue—but not once you know the secrets to identifying and properly using each of these green onion types.
Green onions are a species of onion from the Allium fistulosum family. They are either harvested early before a bulb grows from the stem or harvested with the bulb attached. Green onion bulbs are much smaller than the bulbs of a spring onion.
They are mild in taste, so you won't cry while cutting them. The most intense flavor comes from the white part closer to the stem, but the entire green onion is edible and can be eaten raw or cooked. Asian cuisine uses this type onion a lot, especially in stir-fry dishes.
There are 3 correct ways to cut green onions.
Guess what? There's actually no difference between scallions and green onions. The Illinois Times states that the names differ based on geography. The mid-Atlantic coastal states and all of New England call them scallions while the rest of the US calls them green onions.
Finally, a solution to the common "I can't find scallions at the grocery store" problem!
Spring onions are also members of the Allium fistulosum species, and are distinguished by their large bulbs. They are also more slender than green onions.
As you probably guessed, spring onions are called so because they are harvested in the springtime. There's more flavor packed into spring onions compared to green onions, and that's because they are grown for a longer period of time. Spring onions are more sharp and pungent than green onions, but not as strong as yellow onions. They can be eaten raw or cooked and pair well with spring and summer vegetables.
Now that you know the similarities and differences among green onions, scallions, spring onions, and chives, you can use any of them in your cooking with confidence.