Why are my tomato seedlings looking yellow?

[cheapdave]

started some tomatoes - 3 varieties, 6 of each in peat containers...used organic potting mix (from home depot) watering with rain water....they are couple of weeks old. I place them outside whenever it is sunny day...if there is no sun, I use florescent lights 12 hours or so.... several have first true leaves.........none are dark green.....they look sort of light green color....I see the tomato plants in the stores look beautiful lush dark green.........what am I doing wrong?

[Billy]

At a couple of weeks old, they are probably no more than an inch or two (2.5-5cm) tall. Relax. Can put them in the ground until it is 70F.

[David Hare-Scott]

I am thinking they need more light. Once they have their first true leaves I move mine into dappled sun. Then as they get near ready to plant out into full sun.

David

[Billy]

At a couple of weeks old, they are probably no more than an inch or two (2.5-5cm) tall. Relax. CAN'T put them in the ground, until it is 70F. Oh, you can, but not much will happen.

[Pat Kiewicz]

Does the 'organic potting mix' include any fertilizer? It should say so explicitly on the bag. Unless the potting mix comes with fertilizer you will need to add some to your seedlings. Perhaps fish emulsion (if you stick to purely organic). Dilute to half-strength.

You didn't describe your seedlings as being tall or leggy, so I don't think they lack for light. It is possible to sunburn your seedlings if you move them from flourescent lights to full sunlight too quickly. They need to be acclimatized.

[Billy]

If you use fish emulsion, be sure to get "organic" fish emulsion. Fish have become the repositories of human waste like mercury, lead, PCBs, and PBDEs. You don't want to be adding these to your edible gardens.

[Higgs Boson]

He may not have thought to mention "tall or leggy" but that could be happening.

I'd suggest putting them on a table near a window that gets at least a few hours of sun daily. That way they're protected from cold. Turn every day to avoid plant leaning in one direction. Monitor if too much light; if so, move a few inches away. If too many sunless days, resort to grow lights. Put out to harden as soon as frost danger past -- but be conservative; don't rush it; if your area can get sudden frosts. Good luck!

[Dan L.]

Hmmm... Can Chlorosis exist in seedlings? Could be bad seeds?

Grow lights may be better than shop lights for plants. Try transplanting some of the plants to better soil and see what happens. For cold season areas a heated propagation frame is nice to have for seedlings.