Some things to check: First the pot, does it have drainage holes at the low points? If not-- drill holes. Is it the right size for the plant? If you have a dwarf windowbox then 2 gallons might be OK. Second the Mix, does it drain without holding water too long? If not, then repot with appropriate draining mix. Did you have a COMPLETE fertilizer in your initial potting mix including calcium? make sure you do. Next; were you watering when the plant needed it, or on a predetermined schedule? Check moisture at root level with your finger, and look at the plant for wilt. Dont water unless the plant needs it. Are you giving the plant a periodic fertilizer after the initial fertilizer is depleted? The watering of containers with fast draining mix will deplete fertilizer faster than in the ground plants. Consider these questions and how many of these things need to be addressed. This is a a little late in the season for some locations, so some special things may have to be considered due to remaining growing time. Of course one needs to assure the plant has good sunlite and right temperature.

Growing Tomatoes FAQ: What is blossom-end rot? How can I prevent it? Blossom-end rot is a disorder of tomato, squash, pepper, and all other fruiting vegetables. You notice that a dry sunken decay has developed on the blossom end (opposite the stem) of many fruit, especially the first fruit of the season. This is not a pest, parasite or disease process but is a physiological problem caused by a low level of calcium in the fruit itself. Symptoms BER, or blossom-end rot usually begins as a small "water-soaked looking" area at the blossom end of the fruit while still green. As the lesion develops, it enlarges, becomes sunken and turns tan to dark brown to black and leathery. In severe cases, it may completely cover the lower half of the fruit, becoming flat or concave, often resulting in complete destruction of the infected fruit. Cause Calcium is required in relatively large concentrations for normal cell growth. When a rapidly growing fruit is deprived of calcium, the tissues break down, leaving the characteristic lesion at the blossom end. Blossom-end rot develops when the fruit's demand for calcium exceeds the supply in the soil. This may result from low calcium levels in the soil, drought stress, excessive soil moisture, and/or fluctuations due to rain or overwatering . These conditions reduce the uptake and movement of calcium into the plant, or rapid, vegetative growth due to excessive nitrogen fertilization. Management Adequate preparation of the garden bed prior to planting is the key to preventing BER. Insure adequately draining soil in the bed by adding needed ammendments, maintain the soil pH around 6.5 - a pH out of this range limits the uptake of calcium. Lime (unless the soil is already alkaline), composted manures or bone meal will supply calcium but take time to work so must be applied prior to planting. Excess ammonial types of nitrogen in the soil can reduce calcium uptake as can a depleted level of phosphorus. After planting, avoid deep cultivation that can damage the plant roots, use mulch to help stabilize soil moisture levels and help avoid drought stress, avoid overwatering as plants generally need about one inch of moisture per week from rain or irrigation for proper growth and development. Once the problem develops, quick fixes are difficult. Stabilize the moisture level as much as possible, feeding with manure or compost tea is recommended by many, foliar applications of calcium are of questionable value according to research because of poor absorption and movement to fruit where it is needed but many have reported that foliar application of magnesium (epsom salts) can effect added calcium uptake. Other various suggestions consist of powdered milk, crushed egg shells tea, bone meal tea, Tums tablets, etc. but prevention is the key. Some recommend removing affected fruit from to reduce stress in the plant. BER should not be confused with fruit abortion or inadequate pollination although the symptoms may appear similar. The onset of BER occurs only after the fruit is well on it's way to development while insufficient pollination problems terminate the fruit while still quite small. Here is a link that might be useful: BER FAQ

The problem is that almost ANY variety can develop BER in a given season. Variety X that has BER this season may not have it next season. And that's b/c of all the environmental variables that change from year to year. The main cause of BER seems to be uneven moisture delivery, so tell that to the weatherpersons, LOL, as well as growing in soil that's too rich re N, or if it's too hot, too cool, too dry, too wet, just so many variables to deal with. In other words, stresses to the plants. But it is true that paste tomatoes are more susceptible to BER and many of them are also prone to Early Blight ( A. solani) as well. BER is seldon due to a lack of Ca++. Data has shown that tissue taken from plants that have BER fruits has plenty of Ca++ in those tissues, but the problem is maldistribution of Ca++ within the plant such that Ca++ doesn't get to the blossom end of fruits. So it's usually not lack of Ca++ that's the problem, rather, the variables I mentioned above. Often folks will add Ca++ in some form and think that it has cut down on BER when in fact BER usually goes away as the season progresse b/c the more mature plants can better handle the various stresses that they might face. if soils are too acid then Ca++ can be bound in the soil, but that's rare, and if there's NO Ca++ in the soil, then that's a problem as well, but that condition is also very rare. One might think that all tomato varieties have the same physiology when it comes to transport of minerals and nutrients within a plant but the susceptibility of paste varieties as well as seldon seeing BER with cherry tomatoes says differently. And one can also see the difference if plants are deluged and sitting in water, at least I have, where some varieties can withstand that and others turn yellow, then brown and then die ASAP. So there have to be differences in how certain varieties deal with root uptake and dissemination of water and minerals and nutrients within plants. I know some folks just cut off the BER affected areas and eat the fruits but for some reason I find BER fruits to not taste good so I just discard them. Hope that helps. Carolyn

Hey Rick, I could very easily be the temperatures. Or any number of factors.... Carolyn137 wrote an excellent response to a question about Blossom End Rot (BER) and I am quoting it here: With BER there is NO problem with absorption of Ca++ though the roots. The problem is maldistribution within the plant that can be induced by a number of stresses which include uneven delivery of water, too much N, growing in too rich soil, too hot, too cold, too wet, too dry you name it. As the plants mature they can better handle the streses that can induce BER so usually it goes away. The two exceptions are first, if the soil has NO Ca++ as confirmed with a soil test, and that's a rare condition, and second, if the soil is too acidic in which Case Ca++ is bound in the soil. Again, adding lime, egg shells and on and on can not and will not prevent BER b'c absorption of Ca++ thru the roots is OK. Paste tomatoes are especially susceptible to BER and I think someone in a post above mentioned that. If you go to the top of this first page and click on the FAQ link and scroll down you'll also find an article about BER in case some of you have never looked at the FAQ's And there's some darn good articles there as well, but I wouldn't pay any attention to the variety list b'c it's way out of date. The old information about BER being caused solely by lack of soil Ca++ has been shown to be wrong with research that's been done in the last 20 years or so, but it's going to take another generation before the real story gets into books, websites, magazines, etc. Most of the better websites already have the correct information. BER affects not only tomatoes, but peppers, squash, cabbage, cauliflower, etc., and it's a huge multimillion dollar problem for the industry, which is WHY all that reasearch was done. For instance, when tissues were taken from a plant that has BER fruits and was assayed for Ca++, the normal level of Ca++ was found, it just wasn't getting to the blossom end of fruits. And there's also a condition called internal BER where the fruits look fine, no evidence of BER externally, but when you cut open the fruit the inside is black Hope that helps Betsy