Shouldering Up: Treating Discolored Shoulders on Tomatoes

“I’ve been gettin gyellow shoulders on my tomatoes.  Purchased last year and planted the seed both years.  It didn’t happen last year.  Does your seed go bad that fast? What disease is included in them?  ~Very Disappointed Customer”


Dear Very Disappointed Customer,

Thank you for the letter regarding the yellow shoulders on your tomatoes.  Thankfully, the discoloration you are experiencing is an environmental effect on the fruit of the tomato and not a disease.

What you are seeing with your tomatoes is the lycopene degradation.  It is brought on by intense heat or light has probably prevented lycopene production.  As a tomato fruit ripens, the chlorophyll within the cells degrades, leaving the fruit a greenish-yellow color.  Normally, that yellow coloration is not noticed because the lycopene enhances during the ripening process and the two ‘swap’ places, so to speak.  However, intense heat or light can damage the chemical pathway that develops the lycopene and prevents the process from continuing.  Without lycopene, the ripening process does not occur as it normally would and the tissue in that area remains hard.

What can you do to avoid yellow shoulders? Here are a few easy steps:

(1) Select varieties of tomatoes that are less prone to yellow shoulder, e.g., cherry tomatoes.

(2) Pick tomatoes at the “breaker stage” when you first see pink color and let the fruit ripen at room temperature.  While some people swear by this, I find that the taste  is similar to a hydroponic tomato.  (This is probably more of a mental thing on my part, but if you a fussy about things like that, keep it in mind.)

(3) Be sure your plants get enough potassium fertilization (Epsom Salts work great!).

(4) Make certain your plants have enough leaf cover so that ripening tomatoes are shielded from intense heat and light.

For more information on this disorder, or to quench your plant biochemical curiosity, check out these university websites and professional journal articles:




© Mertie Mae Botanics LLC and Horticulture Talk!, 2010. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Mertie Mae Botanics LLC and Horticulture Talk! with appropriate and specific direction to the original content.


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