Tomato Seedlings

scrib2222February 7, 2013

Hello everyone, I need help. I purchased Costoluto Genovese tomato seeds and planted them a month ago. When the first true leaves emerged, I transplanted each of them to their own pots. They are currently under a fluorescent light that is suspended by chains from the ceiling. There are only a couple of inches between the light and the seedlings. The seedlings were thriving for a couple of days but have since started wilting and the leaves are now turning yellow. At first I thought that I watered them too much so I then transplanted each of them to new pots and added just a little bit of moisture- needless to say they don't look good at all. Is it too late to try to save them? I have attached pictures as well - not sure if anyone can offer advice based on the pictures. Thank you in advance for any help.

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My guess is that those lights are pretty hot so they may have gotten burned. In my opinion, it's a fickle thing to get the light intensity high without burning the plants. Tomato plants are pretty resilient and they would probably make it if you kept with it. I have had some heavily damaged tom plants make a remarkable turn around. For example I had a mouse totally defoliate a plant just after it was planted. All that was left was a stick, which I left in the ground. In a few days a bunch of new leaves sprouted out of the stem and the plant ended up producing tomatoes. The only unknown with it is if there are lingering effects when the plants get older. I have seen that too. For example cat facing on the fruit from too cold of exposure when young. I would say that if the part between the two codelydons is still green then the little plant will probably make it. If that is burned or yellow, throw it out.

    Bookmark   February 7, 2013 at 11:04PM
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missingtheobvious(Blue Ridge 7a)

Kevinitis, I start seedlings under "cool" fluorescents, just an inch or so above the leaves, and have never had a burned leaf -- even when the plants grow up against the tubes.

scrib2222, is the white circle another light? What type and strength is it?

The seedlings look too small to have been planted a month ago. Other than that, I can't say. (I'm naturally suspicious of peat pots, but you say you didn't start with those.)

    Bookmark   February 8, 2013 at 2:04AM
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What I see is plants that are not absorbing nitrogen. Here are some things to check for.

Temperature - tomato seedlings grow best between 65 and 72 degrees F. If your temperatures have been below 60 for any length of time, nutrient imbalances can occur depending on variety. If they get below 50 degrees, then physiological changes can kill the leaves. The cure is to raise the temp to 90 degrees for a few days which will reverse the effects of being too cold.

Nutrients - Seedlings need the equivalent of 1/4 teaspoon of miracle grow 15-30-15 applied twice to 50 seedlings to get them to 8 inches tall. If you have been using organic fertilizers, please check the nitrogen content. This is the most likely source of problems with your seedlings.

PH balance - tomato seedlings grow best at 6.5. If you are using commercial seed start mix like promix-bx then this is not likely a problem.

Phytothora/overwatering - or other microorganisms propagate in soil and can demolish the root system in about 24 hours. This is ALWAYS associated with some amount of overwatering and is usually a result of using contaminated soil.

In my opinion, bright sunshine will help your plants, BUT since they have been grown under lights, you would have to harden them off before they could handle the UV. Given their condition, the additional stress of hardening off may finish them off.

One other note, lots of folks use the various forms of peat pots or cow pots or peat plugs to start seedlings. These all wick water from the soil and evaporate it into the air. The evaporation can cause evaporative cooling under some conditions which is like giving your tomato roots an ice bath. The excess evaporation also means they must be watered very regularly. I won't say outright to not use them but would suggest that a seed start tray is a smart investment.


    Bookmark   February 8, 2013 at 3:27AM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

Lots of good info above. The white, what appears to be a heat lamp or incandescent flood, first caught me eye as well. A great deal of heat there.

But I'll go a step further than Darrell and say one should never use peat pots. The problems they create far outweigh any possible advantages to their use. Even an old plastic yogurt or cottage cheese container is 10x better. So my first move would be to transplant them out of those ASAP.

But we need answers from you to all the questions posted for more help.


    Bookmark   February 8, 2013 at 11:32AM
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helenh(z6 SW MO)

I had trouble with organic Jiffy mix. I think it is your potting mix holding too much water. What potting mix are you using?

    Bookmark   February 8, 2013 at 12:17PM
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missingtheobvious, yes with florecents, heat is often not a problem. It looked to me like in the pic he had incandecents, which put off more light intensity but also more heat. I have used both and had burn problems with the incandecents. With florecents I had problems with low light intensities which caused sun scald problems when you move them to the outdoors for hardening. If you don't have high enough light intensity then you have to be really careful when hardening them off. Even a short duration of sunlight can scald young plants when they were grown under grow lights with insufficient light intensity. If you have exposed your artificially ligted plants to sunlight light for even a half hour on a bright day, you could have experienced sun scald. I try to introduce my young seedlings to natural sunlight as much as possible, as soon as they sprout. That way they develop protective pigments in their tissues early. Sometimes that's not possible, but I do so whenever I can. I have had much better success with hardening them off that way.

Light duration could also be an issue. Guidlines for indoor lights for tomato growth are often 18 hours and some sources even suggest keep the lights on them 24. Longer duration of light is needed when using artificial light because light intensity is lower. However, I don't recommend 24 hours based on physiological reasons. Plants need darkness for some phases of photosynthesis and respiration, without which they develop excess sugar build up in the leaves which can cause yellowing and leaf damage. How long are your lights on?

I also think you should evaluate the factors that fusion_power and digdirt recommended. You might have more than one thing going on there and they are right on about what it could be. If you cover those bases you will probably have your problems solved.

    Bookmark   February 8, 2013 at 12:23PM
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