Most likely IME - too wet soil. It's the cause 90% of the time. Leads to root rot, nutrient deficiency symptoms, and death from the bottom up.

Second most likely - plants are root bound in their containers. Symptoms are the same as you describe plus the plants tend to wilt a bit between watering.

Could be a combo of both.

Dave

no, they are not root bound. I planted them up about a month ago into quite large containers. The design of the containers does not allow for root boundness(you'd have to see a pic)

Too wet of soil. Possibly, but I haven't been watering them.
The soil seemed to be between damp and dry from top top bottom.
I watered two days ago them and they perked up quite a bit, but the bottom leaf die off continues.

Thee conditions are *quite* humid with little air movement.
Home made green house like thing.

Thanks for the tip!

I think you're right, even though the conditions
don't match quite match.

I dissected a couple of "volunteers".

Their starter pot root balls never really grew
(simulating root bound-ness) and they are
brown the the ends of the roots.

I am assuming tomato roots ????should not be brown??????

Luckily when I repotted them I buried deep.
The inch or so that I covered the stems
all have really strong looking beauty roots.
Kinda short still 1/4 - 3/4 of an inch long.

I wonder how the original root ball rotted.

Maybe i'll pro-bmx w/ fungicide next year.

Nope, they shouldn't be brown. ;) That's root rot.

The "original" root ball may have been root bound or overly compacted when transplanted. In that case you need to break it up a bit before transplanting.

Primarily I used last years potting soil from
self watering containers.

Used potting mix tends to compact more so than fresh. Good idea when using it to mix in some fresh stuff with it before re-using to loosen it up.

The MG with Moisture Control added is quickly getting a reputation among some growers as keeping stuff TOO wet - especially when used in small containers. Just something to consider.

Dave

last years potting soil or potting mix ?
I would never reuse any material a plant has grown in w/o sterilizing but would only use then at plant out time and never for starting seedlings - the root rot could be cause by compacted soil as mentioned , by over watering or by a fungus that cause root
Always start seeds with fresh seed starting mix and a good mix when potting up (pro-mix BX or metro mix)and when finally transplanting to there final growing medium
when using old or pre used mix use sterilized and add some new mix
Miracle grow will work for plants but unless really diluted is not good for seedlings. I do not use any fertilizers but if I did suspect the need to add it would be diluted seaweed, fish, kelp extract
Dennis

Too wet is normally an issue, but do not forget about the lack of Magnesium ( virginia tech coop printout) "lower leaves turn yellow along the tips and margin and between the veins, the lower leaves wilt. Calcium Young stems and new leaves die. Good luck

Without seeing your plants I can not compare to what was happening to my tomato seedlings. Almost all of my started to turn yellow also. They were all in 3" peat pots, new Pro-Mix BX under T-5 lights, 4 weeks old, and I do not over-water my plants. I uploaded pictures of my plants and within a couple of hours some awesome people in here told me exactly what was wrong. The best way I can explain what was happening to my plants was....I needed to get ironite into them asap. I was giving them a weak solution of miracle grow every other feeding, but for some reason they were not absorbing it. It has been 2 weeks now since that was happening, and my tomato plants are doing beautifully. They are very happy, green again and growing well. I did lose about 12 plants though, they were just to far gone. The diagnosis that my plantlings had was "clorosis" ....all is well now. I wish you luck. I was also stressing out at the time.

MVIsland, the diagnosis of your problem was INTERVENAL Chlorosis ... lacey yellowing between the veins of the leaves ... caused by micronutrient deficiencis, usually iron or magnesium. That is why I recommended Ironite or Fertilome iron supplement. Also, as Mulio said, a good Miracle Gro type tomato food should contain all those micronutrients, but I recommended the Ironite + Epsoms salts as a booster.

What Elskunkito describes sounds more like classic nitrogen deficiency caused or compounded by chronic wet root ball causing rotted roots which then cannot take up sufficient nitrogen and phosphorus (he noted some stiff purple stems along with the gradually yellowing leaves).

Without pictures, I cannot confirm the diagnosis, just the same as I needed pictures of your plants to confirm micronutrient deficiency witnessed by intervenal chlorosis.

However, what elskunkito describes, and he describes it quite well, SOUNDS LIKE gradual and general chlorosis moving from the lower and outer extremes upward through the plant.

Why is this nitrogen deficiency (most likely)? Because nitrogen is mobile in the plant. That is, the plant is capable of moving nitrogen from where it is least needed (the cotyledons and lower, older leaves) and transporting it to where it is most needed (the growing tips). Nitrogen is essential for photosynthesis, cell division, new growth and starch (sugar) production.

Why is there no nitrogen left in the old potting soil? Because nitrogen is volatile and evaporates into the atmosphere or is washed out of the potting mix by irrigation. Nitrogen must be replenished into the soil in regular dosings for proper plant health.

Lastly, folks who continually repeat the old saw that seedlings do not require fertilizer are doing no one any favors. Stop it please. This instance with elskunkito's excellent description of symptoms as well as MVIsland's previous problem two weeks ago are just 2 recent instances that clearly prove growing tomato plants require proper nutrient feedings. In elskunkito's case, he clearly stated his plants are 8 - 10 inches tall with minimum 3 sets of true leaves ... and "a couple months old." THEY NEED PLANT FOOD!!!

My caution to you all is to ignore these folks who repeatedly say tomato seedlings do not need plant food. They are only repeating bad, incomplete, uneducated information they have gleened from other uninformed or improperly informed people at other websites, IMO.

Without pictures, I cannot confirm the diagnosis

I can't post a pic for another day or two but
I am not sure if it would do any good now.

I dosed the plants yesterday with worm poo juice* + water
and an additional layer of high N potting soil.

Some plants grew a 1/4" inch already.
They seem way more green and perky.
Somehow they just look 'healthy'.

Is that fast a turn around possible?

Or maybe its mostly optical illusion because I removed all the dead and dieing leaves.

I have some ironite + epsom on hot stand by but I am afraid
of over watering now.

Normally I use only 'sterile seed starting mix'
This year I was lazy, impatient and in a hurry.
I remember convincing my self 'it doesn't matter'.

Never again.

Thanks again all.

*made mostly from digested coffee grounds.

Lastly, folks who continually repeat the old saw that seedlings do not require fertilizer are doing no one any favors. Stop it please. This instance with elskunkito's excellent description of symptoms as well as MVIsland's previous problem two weeks ago are just 2 recent instances that clearly prove growing tomato plants require proper nutrient feedings. In elskunkito's case, he clearly stated his plants are 8 - 10 inches tall with minimum 3 sets of true leaves ... and "a couple months old." THEY NEED PLANT FOOD!!!

My caution to you all is to ignore these folks who repeatedly say tomato seedlings do not need plant food. They are only repeating bad, incomplete, uneducated information they have gleened from other uninformed or improperly informed people at other websites, IMO.

You are quite correct hoosier. These are not seedlings. They are plants. Yet even you seem to be using the terms interchangeably in your criticism of those of us who council, knowledgeably, that seedlings do not require feeding.

But plants and seedlings aren't the same thing. Plants need feeding. Young seedlings do not need and can in fact be harmed by fertilizers. Not pointing that out would be doing the disservice.

So when I make the claim that seedlings do not require fertilization I mean just that - young seedlings.

Dave

Dave, I'm not sure what you mean about inconsistent advice. Basically, I think a plant, whether seedling, transplant, blossoming, post-fruit set, fully mature, whatever stage of growth, will let you know when it needs feeding by exhibiting visible signs of nutrient deficiency.

Some young seedlings can make it to transplant without fertilizer in addition to whatever is in the initial starter mix. Yes. But some cannot. And those that cannot will clearly show you symptoms of nutrient deficiency. And I've only been trying to point out what those symptoms are in relation to the specific deficiencies.

Additionally, all tomato seedlings will benefit by sufficient uptake of phosphorus early on. And by that I mean at and immediately following first true leaf stage. This has been proven by lab tests using marked phosphorus that later is tracked to the first blossoms and initial fruit.

Also, it's my opinion that a lot of what folks complain about older varieties like Brandywine being unproductive is directly due to lack of proper feeding both at the seedling stage and throughout the growth cycle. Those are some monster, indeterminate plants and they need food. And you can improve their fruit setting capacity with early feeding, in my opinion. Yes, even at the seedling stage.

So again, it's my opinion that all this advice about not feeding tomato seedlings is generalization and not addressing the specific needs that are expressed by the plants and clearly seen if you know what to look for and how to diagnose it. Too many people are tossing these generalizations around as if they are gospel ... just cuz they read it somewhere on the Internet.