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What causes pumpkins to turn orange? Well they're not always orange! They can be white, red, yellow, green, even blue! This "Never Stop Asking 'Why?'" answer is brought to you by eHow!
Pumpkins change color from green to orange for the same reasons tree leaves change color in the fall, and they do it under the same conditions. Most pumpkins contain organic pigments called carotenoids that give their flesh and skin the classic deep orange tint. Not all pumpkins turn orange, though -- some are selectively bred to be white, red or even blue.
Here are a few factors that lead to a pumpkin's color:
Day length
With the longer nights of fall, pumpkins on the vine gradually slow down and stop their production of chlorophyll. This green pigment, necessary for photosynthesis, degrades and the carotenoids are revealed, causing the pumpkin to change color to shades of orange, red and yellow.
With the longer nights of fall, pumpkins on the vine gradually slow down and stop their production of chlorophyll. This green pigment, necessary for photosynthesis, degrades and the carotenoids are revealed, causing the pumpkin to change color to shades of orange, red and yellow.
Temperature
Warm, sunny days and cool nights with no freezing temperatures can accelerate color changes in both pumpkins and fall leaves.
Moisture
How much moisture is in the soil affects when pumpkins turn orange. If the summer has been a dry one, the color change may be delayed.
Because of their orange color, carrots and sweet potatoes also contain lots of carotenoids. Some carotenoids show up as a yellow color rather than orange and are dominant in vegetables such as corn and fruits such as bananas. Even some green vegetables, including spinach and broccoli, have large amounts of carotenoids hiding under all that deep green chlorophyll.
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