Why yellow shoulders & cracked stem end?

by Richard
(Indianapolis, IN )

Q. It's the summer of 2011, the place central Indiana. I've got 600 plants (12 varieties). The season started too wet, then too dry, then too hot (100 degrees at times) then too wet with 3 inches of rain in one day, then dry again.

The result is 30 - 40 % of the tomatoes have yellow shoulders & cracks across all varieties, except the yellow variety, which has just a few cracks. I understand the cracking is probably due to dry/wet cycle but I have never seen the yellow shoulders. Can you explain what's happening? Thanks.

A. What a tough season for you Midwest gardeners!

You've got two different issues going on here, as you outlined so logically.

1. Cracking. Dry weather that gives way to excessive watering or a rainy period can lead to cracking.

• Tomato plants get too much water too fast.
  
• A tomato’s interior grows quickly as it absorbs the extra water from rain or disproportionate watering, but it expands too fast.
  
• The tomato skin can’t stretch to accommodate the extra fluid.
  
• Cracking alleviates pressure.
  

You can't do anything about Mother Nature. However, next year you can plant crack-resistant varieties. If possible, keep plants well-watered during dry and hot spells to allow moisture levels to be consistent in fruit.
(Read more about cracking.)

2. Yellow shoulders. Tops of your tomatoes aren't ripening as the rest of the fruit does, leaving them a yellowed color. Most likely, high heat and light (during your 100-degree hot spell) prevented the proper production of lycopene, the pigment responsible for a tomato's red color. You can prevent or slow yellow shoulders by providing shade during intense hot spells. You can also pick tomatoes when they first start to ripen, allowing them to finish the process inside and out of the direct, driving light. Some gardeners purposely plant varieties that are less susceptible to yellow shoulders, such as cherry tomatoes.

Good Luck and Happy Gardening!
Your friends at Tomato Dirt