Purple leaves on seedlins is actually quite common I am told. BUT a few weeks ago i was panicing also. Lol. It has to do with cooler temperatures making it harder for the plants to get the phopherous(sp) I believe. They will grow out of it

More info in link below.

The consensus seems to be that it's not harmful and it will just go away or stop happening.

Here is a link that might be useful: Purple stems/leaves

Purple leaves are normal in seedlings, more so in some varieties than in others. We all have them to varying degrees and it often comes up for discussion the first time someone notices it. ;)

It is a result of the cooler growing conditions and the stresses associated with growth that may temporarily interfere with the plants ability to absorb and use nutrients. It goes away all on it's own as the plants mature. Don't worry about it but do make sure that you aren't over-watering them as that only makes it worse.

Dave

Thanks for the replies!! The plants are in my dining room, which is one of the colder areas of my house. At worst, it is probably around 60 degrees at night. Do my babies need a little space heater to take the chill off at night???

Also, the first set of leaves (not the true leaves) are turning yellow and dying. Is this normal?

I'm glad you posted this, because my brandywine, cherokee purple, and mortgage lifter leaves are the same way. Thanks!

EG

ccaggiano - no they don't need a heater but it does sound as if you may be over-watering. Purple leaves as I said are made worse by excess watering as it increases the stressors and yellowing cotyledons is also a sign of too much water. Yes it is normal for them to die...eventually. But please try cutting back on the water a bit too. Too much water is worse than too little. ;)

Dave

I'm saving up to buy one of those Eden Pure heaters for my greenhouse. :)

Diagnostics:
Purple under leaves of tomatoes is a trait of phosphorus deficiency. This is the most telling trait of that deficiency.

The yellowing of seedling leaves (lower part) is the deficiency of a mobile nutrient. The plant takes the nutrient from the lower leaves and moves it up to the growing portion at the meristem. Phosphorus is a mobile element. These two factors together diagnose your plant as definitely phosphorus deficient.

Organic miracle grow is great, but tomatoes are heavy phosphorus feeder. Phosphorus is found in the soil in small, ever present amounts that are broken down from soil minerals (making it a bit different from Nitrogen in that respect). This will probably clear up once you get them into the ground with some nice soil and cations :) .

If your plant were large enough to bear fruit, lower leaf chlorosis could be caused by an Mg deficiency.

My advice is to transplant them as soon as the LFFD occurs. If you cannot, adding a bit of regular miracle grow solution may solve the problem (use the weak, smaller scoop, well diluted as directed) until you can get them into their final home.

marandalovesveggies - the plants in question here are young seedlings, not established plants.

While P deficiency may exist in some garden soils, it would be rare to find it especially lacking in any average new potting mix. At least no more so than any other nutrient may be lacking.

Many recent studies show that tomatoes plants require no more P than they do any other nutrient or micro-nutrient and that P is just as easily mobilized as any other nutrient by the plant.

So while the "purple leaf/stem" symptoms may signal nutrient deficiency in established plants and may need to be addressed, in young seedlings it is honestly extremely common and quickly disappears as the plant and its circulatory system matures. Attempting to "cure" the symptom by over-dosing it with nutrients that it can't yet handle only stresses the young seedlings even more.

Dave

I have tomatoes growing on my bay window sill. They have extremely deep purple undersides of their leaves. The tomato plants growing of the same variety 12 inches away on a table in front of the bay window are not purple. I think it has to do with the cold. We have been getting some night below freezing. The purple tomato plants on the window sill are much healthier and larger looking then the ones further away due to more sun light near the sill despite the cooler conditions.

It has to do with cold : NOT cold air but cold SOIL, that the roots cannot uptake the nutrient, especially "P"

Too much watering (with COLD water) can also aggrevate it.

THAT IS WHAT they SAY.