Ideal Conditions

• Burrows and Graper stated that tomato plants produce most abundantly with day temperatures between 70 and 75 degrees and night temperatures around 65 degrees. Higher daytime temperatures result in more flowers, but since production of pollen is reduced above 80 degrees, less fruit will be set. Higher than ideal day temperatures are partially offset by cool evenings, they noted.
  
  

Blossom Drop

• Oklahoma Cooperative Extension Service warns of a condition called blossom drop, in which the flowers of the tomato plant fall off before setting fruit. This condition is caused when day temperatures remain above 92 degrees or night temperatures are consistently below 60 degrees. Blossom-set sprays, which mimic plant hormones, help the plant retain blossoms and set fruit if cool nights are the problem, but they have no effect when high day temperatures are at fault.
  
  

Cracking

• Hot, dry periods or extreme temperature shifts during the growing season can affect the quality of the fruit, Burrows and Graper noted, causing the skin of the ripening tomatoes to crack. Home growers can decrease the incidence of cracking during hot periods by keeping the soil uniformly moist. During periods of extreme temperature variation, pick the tomatoes before they are fully red and allow them to ripen indoors.
  
  

Catfacing

• Too little heat during the days just before blossoms appear cause another aesthetic problem in tomatoes, called catfacing. Scars or bumps form on one end of the tomatoes and disfigure the fruit. Burrows and Graper said home gardeners can reduce the problem by using plant varieties that produce smaller fruit, since these are less susceptible. Excessive nitrogen worsens the problem, so take care when fertilizing. Catfacing does not affect the flavor of tomatoes; simply cut away the affected area before eating.
  
  

End-of-Season Temperatures

• When cooler autumn temperatures arrive early, or if there is still an abundance of unripe fruit on the vine at the end of the growing season, the lack of heat will inhibit the ripening process. Oklahoma Cooperative Extension Service recommends the following method for overcoming the problem. Remove all green tomatoes from the vines before the first frost. Wrap them individually in newspaper or waxed paper and store them in a dark place at about 60 degrees. Check often for tomatoes that have turned pink, unwrap them, and allow them to fully ripen in a room heated to about 70 degrees. This method should yield a continuous supply of tomatoes for one to two months.