Small space gardening, cooking, and crafts

Blossom Rot - How to Save Your Tomato Harvest

With the hot and hazy days of summer ticking away, my itsy garden has suddenly sprung into a jungle of produce. All of that careful planning, construction and tending has finally begun to pay off in pounds upon pounds of fresh and delicious veggies!

With dreams of pickles, hot sauce, dried chilies, pesto and fresh herbs finally becoming a reality, I looked anxiously to my tomatoes. Would they similarly thrive in the containers I had chosen? Were they getting enough sunlight to produce those amazing San Marzano fruits? As dozens of little yellow blossoms formed on what can only be described now as 'tomato trees', I allowed myself to imagine the taste of amatriciana sauce in the middle of winter freed from the confines of a Bell canning jar.

(Tall as these plants are in the photo, they now reach the height of the humming bird feeder and recently required some new bracing, but more on that growth spurt later.) 

From each set of yellow blossoms that the tiny pollinating bees having been loving so much soon sprung my first green tomatoes. 

Sweet success!  Bunches of perfect fruits soon followed on all of the plants and I foolishly thought that nothing could stop the bumper crop of my dreams from happening! That was, until I spotted this...

Nothing to worry about, surely. My plants were green and growing like weeds, this was just an anomaly. Nope. More like a warning of worse to come. Here is a picture of one of my vines overhanging the balcony on the same day I shot the above photo:

Green, growing tomatoes, but I should have noticed the browning of the leaves on the lower right. Had I acted sooner, I might have avoided harvesting these which ripened a week later:

On the same day as I picked these tomatoes (a mere 7 days after spotting the first blossom rot fruit) this was my overhanging vine:

Shriveling, almost silvery leaves indicating a very unhappy plant. But how could this have happened so quickly? Hydration was never an issue with my rain gutter system suppling a steady amount of water. The root systems that had made their way into the gutter looked lush and healthy and there were no infestations on the upper leaves. Not water, not lighting and not pests, which left me with only one other cause: nutrition. 

Not trusting my potting soil to supply all of the necessary nutrients, I had applied a good quality, organic fertilizer after planting. While this was enough to allow my plants to grow bushy and tall, it was not nearly enough food to support a full fruiting. With container planting, you can control so much of what happens with your plants, but this also means that you must be more aware of nutrient depletion and pH levels. Where you might get away with fertilizing a ground plant once a season, that isn't likely to suffice for a container plant.

Beyond the fact that my plants were due for a feeding, I suspected that my problem was actually two-fold. Allow me to briefly give some details on those conditions for any garden geeks, or feel free to skip ahead for the solution. (*Resources used in the diagnosis of my issue are listed at the conclusion of this article). 

- My first round of fertilizer was not only insufficient to last the season, but it was also not fast acting. In my ongoing attempt to support local business and green initiatives, I chose an organic fertilizer from a company that recycles a number of waste products. It really is a great fertilizer, when used at the right time and in the right situation. The pellets are compacted and did not break down as quickly or completely as I had expected, meaning that much of the nutrient density remained near the surface and out of reach. If this product were used for ground plants that were watered top down, rather than from the bottom like in my system, the pellet breakdown would have occurred more swiftly. Introducing the pellets before planting would also have helped greatly. When I removed my spent Sugar Snap peas from their pots, I could identify a concentration of fertilizer bits which confirmed my initial suspicion. 

-Low soil pH. If you want to go down the rabbit hole of plant germination and fruiting issues, do a quick study on the effects of plant stressors on Gibberllins (plant growth hormones). Suffice to say, disruption there is a much more sound case for blossom rot than the more common claim of calcium deficiency. In fact, calcium deficiency in tomato plants is usually seen -after- the emergence of blossom rot, indicating it more as a result, not a cause. So then why does the conventional treatment of using lime (a source of calcium) seem to work so well against blossom rot?

Because lime raises soil pH, thereby reducing stress on the plant caused by imbalanced soil conditions. While it made sense to assume that adding calcium improved the health of tomato plants as they do require calcium to survive, the raise in pH is now a more acceptable reason for the improvement.

So how can you tell if your blossom rot is due to low soil pH, nutrient deficiency, or both? Get a pH meter. They are cheap from any hardware or gardening center and will potentially save you time which could result in a lackluster crop. Of course you can always go ahead and give your plants some fertilizer if you have neglected the task as I had, which is just normal garden maintenance, but if you can swing the $10.00 for a meter, the results may indicate the need for a different fertilizer blend. As I considered it, I could pay for a meter, or risk losing that much or more in ruined tomatoes. 

Now I should mention that extremes in watering can also act as a stressor that will bring about blossom rot. While this was a controlled condition in my garden, you may need to consider this as a third possible variable in yours. If you find splitting in your tomatoes along with the blossom rot, then the watering cycle may be too erratic. Tomatoes like a consistent watering schedule, so don't allow them to go through periods of drought or over-watering. While we can't control heavy rains necessarily, we can at least avoid thirsty plants, which would go a long way to avoiding the cycle of watering stress.


So how are my tomatoes doing now?

So much better! The last of the affected tomatoes have been picked and all of the new ones are rot free. 

Though I did have to cull a number of leaves, the new growth at the top is again pristine. 

With the addition of fertilizer and some nice warm days, my plants have nearly doubled in size with plenty of new tomato bunches showing up. While I'm excited to see them grow so tall, I suspect that the hummingbirds are less excited about the new obstacles. 


As for the actual tomatoes, these were the last of the young, green ones that started forming right as I fertilized/corrected the pH.:


While we can't always anticipate all of the variables that can cause our plants to falter, we can grow more confident by applying basic troubleshooting:

-Is the plant receiving proper lighting?

-Are the plant's nutrient and soil needs being met?

-Is the plant getting the correct amount of water and drainage?

-How can I protect the plant from invaders?

By asking these four questions whenever a plant becomes sickly, we can narrow down the causes and focus on finding a solution. Add into this the use of tools, such as an inexpensive pH meter, and even the first time gardener can solve most of what might come their way. 


Do you have any tips for keeping tomato plants healthy and producing a high yield? Please share in the comments below! 


*Additional Sources:







Categories: Garden, Highlights

Tags: tomato, blossom rot, soil pH

Comments: 2 Comments

Creative Commons License
This article's still images and text by Sandra Rosner are licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.


  • Comment by Jennifer Oliver on 11 January 2016 3:39 pm

    Thanks for citing your sources. Not only does it lend itself to credibility, it helps me find more to read! ;)

  • Comment by sandy on 11 January 2016 8:45 pm

    Thanks and I totally agree. Not only do these men and women deserve heaps of credit for their research, I can't tell you how often I have clicked on cited sources and went on massive reading binges!

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