Appearance

• On the outside a yellow onion bulb has a dry, mature, brownish-yellow skin. The green onion, which is still immature when harvested, has a white, unformed bulb with long, green stalks. Depending on the variety, small yellow onions range from a little over 1 inch to almost 4 inches in diameter. Green onions, also known as "scallions," are typically smaller than 1 1/2 inches.
  
  

Cultivation

• Growing both yellow and green onion varieties does not require too much soil depth -- an inch in the soil will do. Green onions can be planted in clusters because they are harvested before they grow to full maturity. For the yellow variety, each bulb has to be planted separately from each other to allow it to grow as much as it can.
  
  Both varieties are sown starting late spring. Green onions are harvested as soon as the stalks begin to straighten up in about a month to seven weeks, while yellow onions take around two months. Both varieties require sufficient and appropriate soil moisture, fertility and temperature. Free soil must be pulled towards green onions when the shoots have grown to about four inches in length. Yellow onions do not require this, as it causes bulbs to decay.
  
  

Taste

• Green onions have a subtler taste and lesser essence, as they are harvested before they become fully developed. Yellow onions have higher sulfur content and higher quercetin levels, giving them a stronger onion taste. Both varieties can be eaten raw, depending on a recipe's requirement.
  
  

Common Uses

• Although both onion types can be eaten raw, yellow onions are often used in soups, toppings, stews, and sautéing. On the other hand, green onions are often eaten raw together with their stalks, and often included in salads. If used in cooking, green onions are often added later in the process so they can retain their taste.