Here's one of my earlier posts about blossom end rot:
"See https://ohioline.osu.edu/hyg-fact/3000/3117.html for information and pictures of what that would look like, in a severe case. Blossom end rot is caused by calcium deficiency in stressed tomatoes. The stress can be caused by fluctuations in soil moisture, going from dry to very wet, from over fertilization, or soil that's too acid. It's not a disease and if the conditions are corrected, the plant and future tomatoes will be fine, but the ones already affected are a loss.
Suggestions: Maintain a uniform supply of soil moisture by watering plants during drought and mulching to retain soil moisture. Tomatoes want to stay pretty steadily moist, not go through fluctuations. Avoid using excessive amounts of ammonia forms of nitrogen, which reduce calcium uptake. Avoid overfertilization during early fruiting. Maintain neutral soil pH. Liming helps supply calcium, if soil is acid. Do not subject plants to sudden and severe hardening off before transplanting. Avoid setting plants in the field too early when the soil is still too cold for rapid growth."
It is always a calcium deficiency, but the calcium deficiency is caused by stress, not necessarily lack of calcium in the soil. You have to figure out what is stressing your plant because you know what you have been doing to it and what your conditions have been. Has it been staying evenly moist? I think the water fluctuations are the commonest cause of BER. Have you been adding artificial fertilizer? Growing tomatoes in containers and watering a lot, you probably have to fertilize some, but be careful not to overdo it and look for tomato fertilizer that is 5- 10-10 (nitrogen is the N in NPK, the first number in the ratio) or even heavier on the PK end if you can find it.
Re the topsy-turvy planters. You can search here for that also. People are reporting very mixed results. Keeping the tomatoes out of the ground does reduce risk of soil borne disease and some pests (the same as your deck containers), but you still have all the same issues with how much water and how much fertilizer and what the temps are, complicated by the fact that they have to be small containers to hang them, so you don't have a lot of soil to work with and the roots are right up there exposed to heat and sun, so plants can easily get stressed. I haven't heard much lately since it got to be hot weather from the people who in the spring were posting pics of how great their topsy turvy tomatoes were doing.
Last edited by rainbowgardener
on Mon Nov 16, 2009 11:34 am, edited 1 time in total.