Hardiness Zone: 9b
Raj from Kenya
That's the ironic thing about oranges-they aren't always orange. Depending on the variety, sometimes oranges are green, yellow or even spotted. Temperature fluctuations are what cause oranges to change color while still on the tree. The pigment responsible for orange-colored oranges is called carotene. In order for oranges to turn orange, cooler temperatures are needed. This breaks down the chlorophyll (the green pigment) so the carotenes can show through. In climates where temperatures stay warm all of the time (Puerto Rico, Central America, South Pacific, West Africa), the oranges tend to remain green. Before being sold in the U.S., these oranges used to be coated with an orange dye to make them more attractive to consumers. This practice is no longer acceptable by the FDA, so today green oranges are exposed to ethylene gas while in storage. This removes the chlorophyll layer and allows the orange color to emerge.
Fortunately, the color of an orange has little to do with whether or not it's mature enough to eat or if it will taste good. Apples, bananas and tomatoes all naturally give off ethylene gas while ripening. It might be worth a try to store your green oranges in a cool enclosed area (like the fridge) with one or more of these fruits. Who knows, if enough gas is produced, you might see a color change.
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My sister-in-law had an orange tree in Florida and the oranges were always green! They never turned orange, but they were the sweetest, best tasting oranges I've ever had!
By stang (Guest Post)12/12/2006
"Store Oranges" are dyed for the uniform look. Longer the oranges are left on the tree the "oranger" they will get. They are sweet even if they are only half orange. I live in Centeral Louisiana. Don't know what zone.
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