Oh, I should mention that I have them growing in my basement which is around 65 degrees. I do have a heat mat but I stopped using it about 10 days ago. Coincidentally (or not) the problem has worsened since then. Is the temperature the problem?

Before I posted this I searched GW and really didn't find anything. Then this morning I searched again using a different strategy and realized that topic has been covered previously and there is another recent post in this list that is relevant as well. Anyway, it seems it could be that either the plants are too cool or are low on phosphorous (or a combination of the two). I have put the tomatoes back on the heat mat. I would be surprised that they are low on phosphorous because they are only 1.5 to 2.0 inches tall at this point and are definitely not root-bound. I do have some 8-5-5 fertilizer ("mater magic") that I could sprinkle on even though the plants are quite small. Does this sound like a good idea? Thanks.

Anyway, it seems it could be that either the plants are too cool or are low on phosphorous (or a combination of the two). I have put the tomatoes back on the heat mat.

No sorry but not a good idea. Please take them OFF the heat mat before it cooks the roots. You are misunderstanding the info given in the other posts you read.

The plants are not too cool nor are they lacking in phosphorus. The cause for the purple coloring is their young age and their inability to take up the phosphous that is there because it is being used by the roots right now - just as it should be. The purple coloring is normal. The goal for seedlings is root development, not top growth.

Do not heat them, do not feed them. Just let them do their thing and they will be fine.

Dave

Dave, I would tend to agree except for the fact that on most of the seedlings the older set of true leaves have shriveled up. On one or two seedlings there is only one leaf that looks to be in decent shape and the rest have shriveled up. Also the growth rate is poor. That is what prompted me to put up the post rather than wait it out. Regarding the temperature - what soil temperature is too high for the roots?

The shriveled leaves has nothing to do with the soil temps or the purpling. Something else is causing that, not temperature. We gorw thousands of seedlings annualy and work hard to keep the ait temps between 60-65 degrees.

Most likely cause is over-watering or a poorly draining or contaminated soil. That doesn't look at all like plain old Jiffy Mix in your pics. What is all the other stuff on the top of the cells?

Next most common cause is pests of some kind such as aphids or spider mites.

Once germinated, seedling roots do best at 50-65 degrees soil temp. Established plants can handle much higher soil temps but not seedlings. The effects of putting seedlings on a heat mat has been studied extensively which is why they specifically state they are for germination only.

Dave

our soil looks odd.. I am curious as to what it is. They look pretty wet too. I bet replanting them in some good potting soil and decreasing your waterings will help a lot

Keriann~

I thought the soil looked odd too, but the OP said it was a Jiffy mix. Not something that I use, but I had thought it would be finer (vs. coarse) for germinating seeds

OK, full disclosure :) To keep the initial post from getting too complicated I didn't mention the fact that on the day I posted I up-potted the tomato plants. Up to that point the seedlings were in Jiffy seed starting mix but when I up-potted I made up the pot volume with another mix. Unfortunately, I can't remember the brand but my eggplant and peppers love it. I didn't think it mattered because the purple color and leaf shriveling on the tomatoes had started long before they were exposed to this other mix. So now they are in a mix that consists of both the jiffy mix and this new mix.

Regarding watering, I tend to let them dry on the surface between waterings. I typically pick up the pots/cells to feel the weight before I decide whether to water and how much to apply. But you may be right - I may be watering too much and perhaps this is causing the leaf shriveling. What I can say is that my level of watering is not bothering the peppers and eggplant though they are in a different soil mix. Anyway, I'll back off a bit on the watering and see what happens.

It appears the tomato seedlings are not getting worse since I up-potted so maybe the new soil is beneficial. There is one other piece of information that could be important though. I sometimes notice a few really small flies/gnats around the plants. They are slightly smaller than a fruit fly. Could they be damaging the plants somehow or spreading a disease that could explain the shriveled leaves? Has anyone ever seen this?

I'll try to post better images tonight. Thanks for all your help.

I also grow in my basement, and the temperature has never been a problem for me.

Once my seedlings get their first set of true leaves, as yours have, I transplant them into pots (or small Solo cups) with potting mix. The seed starting mix doesn't have any kind of nutrients and potting mix typically does. Not that I recommend fertilizing them, but the nutrients in potting mix should help give them a boost.

If you're looking for advice, I would say pot them up. Also, it looks like you're watering overhead, is that right? I only water from beneath. That allows the roots to soak up only what it needs without splashing water onto the seedlings which can cause fungus.

Do you have a fan on them? If not, you should. Personally I keep my seedlings on 12 hours on, 12 hours off on the lights. I've never had any problems. The purple leaves could just be the type of tomato you're growing. Some of mine have purples leaves some don't. I'll post pictures for you in case you're interested.

These are Japanese Black Trifele, see how purple the underneath of the leaves are? As far as I'm concerned this is normal, every year I seem to get some variety of tomato with purple underside or cast to the leaves.
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And here is a Big Beef with no purple
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Good luck!

As we have already established the purpling of leaves is normal and nothing to be concerned about. Those who insist on trying to fix it only create worst problems for themselves.

The shriveled leaves is another matter and as pointed out, top watering is to be avoided as is watering based on the surface condition only. It isn't a valid indicator of the need for water at the root level. Both lead to over-watering which causes roots to rot and the older leaves to shrivel and die. The existence of fungus gnats - what you are seeing - is proof of the overwatering. The few you see don't reveal the large numbers of larvae. The larvae exist in the damp soil and eat on the roots.

Re-potting to a drier mix will show temporary improvement since the soil population is temporarily reduced. But if you continue the same watering patterns they will multiply again.

Cut your watering by 1/2 and pick up some Mosquito Dunks to dissolve in your water to kill the larvae.

Dave

PS: full disclosure is ALWAYS appreciated. :)

I think we are zeroing in on the problem - thanks for the advice. I was just reading about fungus gnats as this is my first experience with them. I'll get the mosquito dunks tonight. Do you think watering from below will kill the larvae close to the surface of the soil? Or should I start by watering from the surface a time or two and then shift to exclusively watering from below?

I'm having the same problem with my tomato seedlings. I've grown tomatoes from seed for years and never had this happen before. I'm growning 2 varieties. One is
Cupid grape tomato which I've grown before. The other is Margherita, a saladette variety that I'm trying for the first time. I have never seen seedlings look like this before. Both varieties have the purple stem and underleaf and they are growing slowly and seem to be deformed. I've grown these tomatoes as I always have. The ONE common denominator we have is Jiffy mix seed starter. I just transplanted the seedlings into Metromix potting soil in the hope that they will do better. I'm thinking it's the Jiffy mix that is the problem.

Eaine, I have not had this problem at all this year. Several things are different:

- I have used two different seed starting mixes neither one of which is from Jiiffy. One is from Foxfarm and I can't recall the other but it has some organic fertiizer added to it.
- I have a couple carniverous plants and these have kept away the fungus gnats.
- I started adding Foliage Pro liquid fertilizer to the water very soon after emergence.

My seed starts are the best they have ever looked. By the way last year my plants did slowly snap out of it. I'm not sure if it was the mosquito dunks or the transitioning to the outdoors or the addition of fertilizer. I used a solid fertilizer (formulated for tomatoes) last year.

Steve