Dr. Z: Why Are My Tomatoes Still Green?

Customers have been stopping by the Garden Shop to tell us their beautiful tomatoes are not getting ripe.  They have been sitting there green for quite a while and do not seem like they will ever turn red.
Problems with tomatoes ripening usually occur at the tail end of the season, in the fall, when the temperatures are too cool for the process to take place.  But that is not the case now. You would think that with the extended period of extreme heat we recently experienced that those tomatoes would be getting ripe by the second.  However, it ends up the heat is the problem they are not turning red!  So let's look at what causes a tomato to ripen to its' red color.
First the tomato must mature to the proper size for the variety being grown.  This is called the mature green stage, and it is the stage at which the fruit can turn red.  Next the tomato must give off ethylene gas which aids the process and stimulates other tomatoes in the cluster to ripen.  Finally to get that red color, it needs to produce the pigments lycopene and carotene.  These are only produced in the 50 to 90 degree temperature range.  So when temperatures exceed 90 degrees and remain there for a while, the ripening process stops.
And that is what has been happening recently during this persistent heat wave.
By the way, the optimum temperature range for tomatoes to ripen in is 70 to 77 degrees.  And light, irrigation, or fertilizing will not help a tomato ripen quicker.
Call or come visit Doctor Z to have any of your questions answered.

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