The UC Davis Good Life Garden blog has moved!
You should be automatically redirected in 5 seconds. If not, visit
and update your bookmarks.

Wednesday, July 14, 2010

Tomato Troubles: BLOSSOM END ROT

Tomato blossom end rot is annoying to say the least, but fear not! You are not the only one who has this issue!

Today's entry is an answer for Kate, one of our beloved fans, and addresses the problem that she is having with her tomatoes. Above you will see a photo of her poor tomato. Most of her tomatoes have a hard brownness at their ends. Kate has correctly identified the issue as a lack of calcium, but wants to know what it is and how she can fix it.

First of all, it looks to me like you have a classic case of tomato blossom end rot. The University of California Division of Agriculture and Natural Resources describes the problem in detail in their free publication "Growing Tomatoes in the Home Garden:"

  • Water-soaked spot on blossom end of fruit enlarges and darkens, becomes sunken and leathery. Affects both the green and ripe fruit, and is more common in sandier soils.

Probable Cause
  • Calcium nutrition and water balance in the plant, aggravated by high soil salt content and fluctuating soil moisture.

  • Maintain even soil moisture
  • Amend planting area with organic matter such as compost to improve water retention.
  • Avoid heavy applications of high-nitrogen fertilizer.
  • Soils that are deficient in calcium may be amended with gypsum.
Kate, for some reason I remember that you were concerned about the sandy soil where you planted your garden. If this is the case try amending your soil with gypsum which you can obtain at most nurseries. The packaging will let you know how much to add. Also try to be sure to maintain even soil moisture. If you are concerned that the soil around your tomatoes is not evenly moist then add some compost around your plants to improve the water retention. (On a side note, what is that black and white enamel(?) background on which you took this photo? It looks so cool and vintage!)

Does anyone else have some suggestions? Have you ever added gypsum to remedy this kind of problem in your home garden? How did you do it and what were the results?


kate said...

:) Enamel is a white vintage chair in front yard- I put tomato on- the black is open work :)

My tomatoes are famous. No, soil is NOT sandy- very clay-ey- we added sand in an area for potatoes.
Our friend is a UC farm advisor- sent us this link-

looks like we will try gypsum. the tomato plants right next to the Romas are fine, though...weird....

I want you and Arlene to come see my garden- next week????

UC Davis Good Life Garden said...

Here is a great resource for Tomato Blossom End Rot!

UC Davis Good Life Garden said...

It seems that Roma tomatoes are disproportionately affected by blossom end rot!