Can anyone identify what this is? Blight, blossom rot, something entirely different? This is our first try for tomatoes- container growing. Every tomato that this particular plant has produced has had a black bottom. Leaves look fine. Located in central Arkansas. Any insight appreciated!

Its called blossom end rot and it could be caused by a calcium deficiency. In container grown tomatoes, the deficiency is caused by inconsistent watering. Assuming you used potting soil and are fertilizing with tomato food, there is plenty of calcium in the soil but when it dries too much between waterings, the calcium is not available to the plant.

Another possibility is that you over-fertilized when you planted the tomato in the container. Did you add extra fertilizer to potting soil that had fertilizer already in it?

Pick all the fruit off that has black bottoms. Water enough so the soil is always moist (not soggy wet or bone dry).

Thank you for your response! We used "organic plus" potting mix and also used tomato fertilizer when we potted it. So both are potentially our problem? Should we repot (without extra fertilizer) as well as maintain moisture?

Also, the other four plants do not seem to be affected. We did them all the same.

I would flush it with water really good then keep the potting medium damp. That should wash out any extra fertilizer and dampen the roots well.

Thank you!!!

Pick off those tomatoes and toss. Usually the plant grows out of the BER problems.

hootowlfeathers said:Thank you for your response! We used "organic plus" potting mix and also used tomato fertilizer when we potted it. So both are potentially our problem? Should we repot (without extra fertilizer) as well as maintain moisture?

Also, the other four plants do not seem to be affected. We did them all the same.

Do you know if the "organic plus" potting mix contained any calcium? I looked on Google and didn't see anything by that name. Usually soluble fertilizers don't contain any calcium, so if you're using something like Miracle Gro water soluble tomato food, it will not be providing any so it can only come from the potting mix and/or irrigation water.

Some cultivars are more susceptible to blossom end rot than others which is probably why your others are not affected (or are they all the same cultivar?).

I think it does depend on your region and water quality too. I've never had that issue here, but our water is very hard, and pipes are very old, so water is high in calcium

sooby said:

Do you know if the "organic plus" potting mix contained any calcium? I looked on Google and didn't see anything by that name. Usually soluble fertilizers don't contain any calcium, so if you're using something like Miracle Gro water soluble tomato food, it will not be providing any so it can only come from the potting mix and/or irrigation water.

Some cultivars are more susceptible to blossom end rot than others which is probably why your others are not affected (or are they all the same cultivar?).

I'm not sure about the calcium content of the potting mix (purchased it at Home Depot). The tomato fertilizer we have is a 8-5-5, states 4% for calcium.
They are Cherokee purple heirloom tomatoes. We have two of these plants but this one is the problem child.

I exclusively grow my tomatoes in either containers or Earthboxes (a type of "container"). I use MiracleGro Potting Mix in my Earthboxes and add to this with dolomite (a calcium source: Espoma Garden Lime is organic dolomite, readily available at Lowe's, Home Depot, Walmart eg). For fertilizer for two years, I used MiracleGro Tomato. (Earthboxes have a reservoir of about 3.5 gallons of water, so water is obviously NEVER a problem - unless I forget and let the reservoir go dry!! ).

There are many scientific theories as to what causes BER, how to prevent and/or treat it. There seems to be many causes: erratic watering, insufficient calcium in the growing media, cultivar (my first year, one cultivar/variety had almost ALL f its fruit due to BER, while its companion in the same Earthbox - a different cultivar/variety - only lost a few fruit to BER.), insufficient uptake of calcium by the tomato (fruit), a heavy producing plant (too many fruits starting all at once would exceed the available calcium) etc. And as many ways to prevent it: dolomitic lime, crushed eggshells, banana peels etc. Cures? A popular one (which I used one year) is to make a slurry of the pelletized garden lime (a slurry would be mixing tap water with the lime) and pouring it around the base of the afflicted plant. Another year, I added water-soluble Calcium Nitrate every week during production.

Potting Mixes generally have a very modest amount of fertilizer in them, sufficient for the initial planting only. It causes NO problem!! Neither the potting mix nor MG fertilizer have sufficient quantities of available calcium to prevent BER.

I do not think you need to flush out the potting mix fertilizer (in point of fact, it is almost never done, as it causes no problem needing to be corrected.) I WOULD suggest that you do 2-3 things this year : pick off/throw away all affected fruit, correct/treat with the slurry and add 1 tablespoon calcium nitrate per week beginning ASAP (available at Amazon).

BetNC said:
I do not think you need to flush out the potting mix fertilizer (in point of fact, it is almost never done, as it causes no problem needing to be corrected.) I WOULD suggest that you do 2-3 things this year : pick off/throw away all affected fruit, correct/treat with the slurry and add 1 tablespoon calcium nitrate per week beginning ASAP

Yesterday, I picked off all of the fruit and gave it a super healthy drink (today it has rained). This is the second time this year I've picked off bad fruit.
I do think our watering schedule has been somewhat erratic - so I will correct that. What is the ratio for the lime/water slurry? Is it possible that eggshells would provide enough calcium in conjunction with the calcium in the fertilizer (dynamite mater magic)?

The majority of the time, with container grown tomatoes, the calcium deficiency is caused by erratic watering. If you are still worried, mix 1 tablespoon of Epson salts in 1 gallon of water and spray the foliage. Do it when the sun's not shining on the plant.

DaisyI said:The majority of the time, with container grown tomatoes, the calcium deficiency is caused by erratic watering. If you are still worried, mix 1 tablespoon of Epson salts in 1 gallon of water and spray the foliage. Do it when the sun's not shining on the plant.

"From a review of the relevant literature it is concluded that Ca2+ deficiency is not the cause but a result of blossom-end rot (BER) in tomato and pepper fruit. ............The actual causes of BER are obviously the effects of abiotic stress, e.g. by salinity, drought, high light intensity, heat, and ammonia nutrition, resulting in an increase of reactive oxygen species (ROS), high oxidative stress and finally cell death."

From this 2014 paper on blossom end rot
From: http://www.sciencedirect.com/s...

Daisy, why Epsom salts? It's magnesium sulfate. Tomatoes do need magnesium but blossom end rot isn't related to magnesium deficiency?

[quote="sooby`` . . .
Daisy, why Epsom salts? It's magnesium sulfate. Tomatoes do need magnesium but blossom end rot isn't related to magnesium deficiency?[/quote]

I was wondering that, too, Sooby.

For container growing tomato plants, they usually benefit by twice monthly foliar spraying of an Epsom Salt solution ( 1 tablespoon unperfumed Epsom Salt - magnesium sulfate- disolved in 1 gallon tap water). This is because a magnesium atom is at the center of the chlorophyll molecule, which is responsible for turning sunlight into energy for the plant. Magnesium is needed in very small quantities which is usually ample in the ground, but not in container media. When the top of a growing tomato plant is a lighter green than the bottom, the new growth will benefit by this foliar spraying and reward you (later that day, certainly by the next morning) by turning a uniform dark green!!

I don't have an exact ratio for the slurry; I just wing it until the slurry is a muddy watery mess! The pelletized lime is not water soluble, so the main purpose(s) of making a slurry is to make a pourable mixture . . . pellets are little balls of the insoluble lime rolled in clay and dried.

The Epson salt spray had nothing to do with calcium. Its just another fix for blossom end rot causes.

I was thinking ahead of myself. Water consistently, add calcium then add magnesium. It was next in line...

DaisyI said:The Epson salt spray had nothing to do with calcium. Its just another fix for blossom end rot causes.

I was thinking ahead of myself. Water consistently, add calcium then add magnesium. It was next in line...

I don't know whether magnesium is in the "mater magic" fertilizer, it's hard to find a complete analysis, but if you read this article from Clemson, they say do not apply Epsom salts unless you know magnesium is deficient as it makes plants more susceptible to blossom end rot by competing with calcium for uptake by the plant.

http://www.clemson.edu/extensi...

Presumably that's why you're suggesting to spray it rather than add it to the soil but do you have a research reference that suggests magnesium is involved in blossom end rot?

The "Garden Myths" page on blossom end rot is a bit more blunt than I was lol ". Epsom salts is magnesium sulfate...........it does not contain calcium! Blossom End Rot has nothing to do with a magnesium shortage."

From: http://www.gardenmyths.com/blo...

I found an analysis of "Mater Magic" in the Washington Fertilizer Database, not sure if the link to that exact page will work but here goes:

https://agr.wa.gov/PestFert/Fe...

It contains 4% calcium and 1% magnesium. It doesn't seem to contain much in the way of micronutrients though. Perhaps intended more for growing in the ground rather than containers?

The potting mix is made of "Recycled forest products, coir, perlite, dehydrated chicken manure, composted chicken manure, hydrolyzed feather meal, peat moss, kelp meal, worm castings, bat guano" which suggests it probably also contains calcium - not sure if there is an analysis somewhere......

Okay, I take back the Epsom salt idea - I personally never use it. But will continue to maintain that calcium deficiency in container grown tomatoes is most likely caused by erratic watering. Its also the easiest thing to fix. Water consistently.

Here's a source for you:

http://homeguides.sfgate.com/b...

Agree that erratic watering can contribute, as the Clemson article I linked to above said "Extreme fluctuations in moisture, insufficient soil calcium, root pruning from nearby cultivation, and excessive ammoniacal (NH4 +) nitrogen, potassium, or magnesium fertilization can also increase the chances of blossom end rot."

I'm interested in this because I had the problem last year with container tomatoes, which were not short of calcium (from potting mix plus high calcium irrigation water) nor magnesium (I had used Epsom salts). In fact I had applied Epsom salts because most fertilizers don't contain magnesium. I don't recall having applied as much Mg to them in previous years and had not had BER to the same extent either.

Interesting that the sfgate article cites NGA for suggesting Epsom salts for BER, which is not supported by any scientific research I could find this morning, in fact I found the opposite which is why I'm now wondering if I exacerbated it with the Epsom salts. Will have to look for that page on this site, if it still exists.