Leeks, shallots, chives, ramps and green onions are substitutes for scallions. Scallions are members of the onion family with small white bulbs and tall, narrow green leaves. When the bulbs of a scallion grow to more than ¾ inch wide, the vegetable is considered a green onion.
Leeks, shallots and green onions have similar flavors to scallions, which means that each vegetable can be substituted in equal proportions for scallions in many recipes, such as soups, stews, meat, chicken and vegetable dishes. Ramps, or wild leeks, have a stronger, garlicky-onion flavor. When substituting ramps for scallions, use about half the amount of ramps to ensure that the dish is not over-seasoned.