From reading and inference over the years, I've come to this basic model for 'ripening': (Confidence level is not high.)

  • Photosynthesis in the leaves produces sugars. These are available to nearby fruits. This is good.
  • There's a process in the fruits that converts sugars to starches. This is not good for flavor. Heat and sunlight promote this process. Ergo, tomatoes should be shielded from the sun.

Is this true/sorta true/bogus?

If (sorta) true, does it apply broadly - say to squash, cantaloupes, peppers, ...?

  • 1
    Usually sun-ripened tomatoes are more flavorful and sweet than shade-ripened tomatoes (although it seems that it really depends on the variety, and the specific tomato, in some cases). You might study ethylene, which is a hormone to help fruits ripen. Aug 26 '16 at 22:08

No, it's not even 'sort of true'. Sunlight on tomato plants, particularly intense sunlight, means a lot of photosynthesis is going on, which means the plant can convert carbohydrates (produced by the photosynthesis) into sugars, acids and other flavoursome components in the fruits. Temperature plays a role too - tomatoes prefer to be cooler at night than they are during the day, and there is an optimum temperature range for the best tomatoes. Variety of tomato also plays a role in flavour, sweetness and acidity. Obviously, a balance has to be struck between the fruits getting sunscald in really intense sun, whilst still ensuring maximum exposure to sunlight. More info in the link below


I'm intrigued by your reference to 'process in fruits that converts sugar to starches', and this process being 'promoted by heat and sunlight' - can you provide a link to that information?

  • That is the reason tomato plants have so many arching leaves. Helps to shade their fruits. I got a bit out of control pruning tomatoes once and learned this the hard way. Shoot, I'll just go ask a question for mesef!! And check this link you've sent!
    – stormy
    Aug 26 '16 at 18:54
  • Temp is critically important. If the ambient temp gets above 86 or so for any prolonged period (2+ days) the ripening catalyst(ethylene) production will halt and leaf production will start back up to protect the plant. Slashing and other methods have been used over the millennia to encourage the metabolic response to ethylene. That method allows the decaying portion of the fruit to off gas ethylene. This same premise is why tomatoes will ripen quicker in a paper bag with a banana or other fast rotting fruit. Maintaining connection to the stem while ripening is critical for complex taste. Sep 26 '16 at 16:18

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