Blossom End Rot

Unfortunately, my tomato experiment is not without its troubles. I expected a certain amount of it, but mainly too little sunlight after July and the possibility of drought. I've grown tomatoes successfully before, but never in pots. And I was away for two weeks and worried about the consequences of absentee high-maintenance gardening.

Fortunately, NYC had several thunderstorms while I was away, and it has been that kind of summer- weekly thunderstorm rains. My tomato plants had been watered by the heavy rains from these storms, but while I was away- the plants grew enormously! The leaves shed most of the water that fell on them. Normally this wouldn't be anything to think about, but since my tomatoes are in planter boxes, the surface area of soil is quite small compared to the leaves. So the planters received little of the rain.

Although they had grown enormously while I was away, the tomatoes didn't receive nearly as much water as they had been getting before. To mitigate this, the plants sent fine roots through the planter box bottom to tap the water in the soil beneath. Despite this, my Brandywine tomato plant succumbed to blossom end rot. I've grown tomatoes that have suffered this before and its always such a disappointment when you first see those dark spots under your tomatoes.

Blossom end rot is a symptom of a calcium deficiency in the plant brought on by low water uptake or a calcium deficiency in the soil. In my case, I believe it was brought on by the lack of watering while I was away. My potting soil is mainly seafood compost, rich in calcium (but then maybe salts too, which could limit calcium uptake), so I 90% ruled that out.

These are two Brandywine tomatoes picked because they succumbed to blossom end rot. As you can see, the tomatoes look fine on top.

This photo shows the same tomatoes, but flipped over. The blossom end, has been rotting, turning black in the process. The tomatoes that succumb to this often prematurely ripen.


I threw these tomatoes into the compost heap. Immediately I began watering more thoroughly. I also added some complete organic fertilizer that has calcium (although I still don't believe its a deficiency of fertility in the soil). Finally, I added a home-made slow release watering system made from a 1.5 liter soda bottle. After I filled it with water, I cut a pinhole in the cap and on the bottom. Then I turned it upside down and inserted it in the soil of the tomato planter.

The water lasts about 2 to 3 days. If I continue to get new blossom end rot, then I will know that it is a soil calcium problem, not a water issue. So far, the few tomatoes on the plant have not succumbed. A few weeks will tell.