Lower leaves turning yellow on seedlings

[Tomatovator]

I know I have read something about this recently but I can't find it now. I have a good number of plants that are about 5 weeks old, 5" to 6" tall and in 7oz. cups of potting mix. Most of them look fine. Two Costoluto Genovese and one Early Pick have the bottom 2 leaflets turning yellow. The plants actually look great and are the larger of the bunch. I used some diluted seaweed emulsion about a week ago but no help. The leaves are getting more yellow. I don't think I've been over-watering but who knows could be more dense packing of the potting mix in the affected cups so they are not drying out as fast as the others. I'm not that concerned about curing the condition for now but want to know if the plants will be OK if the bottom leaflets are cut off and they are planted deep when the time comes. I would also like to point out that it is not the cotyledons that are turning yellow. I pinched those off a while ago. It is the first set of true leaves that is turning.

[Tania]

I notice that happens when my transplants are kept outside under lower than optimal temps and when the soil in the containers is too wet. I think roots cannot take up all the moisture/nutrients when the soil is too cold.

I didn't look into any scientific explanation of this phenomenon, since it really hasn't been a huge issue for me - all these seedlings recover nicely once transplanted into a warm garden soil when the weather warms up. I remove the affected leaves.

[scottfsmith]

I'm having that problem now due to all the cold and cloudy weather we are having lately. The plants are in a greenhouse where it is somewhere between the house temps and outside temps. I am using the same pots, soil, etc as last year so I think its the cold that is doing it, confirming Tanias observations. The tops look good so I'm no too worried.

Scott

[WildLife]

Yes too cool, too wet, not enough sun.
Let them dry out

[the999bbq]

yes have to agree with wildlife, yellow is too wet for the opinion of your plant... is there a reason why you pinched out the 'baby' leafs ?

[kudzu9]

My greenhouse-grown heirloom seedlings were all getting lower leaf yellowing and getting light green overall...it has been too cold at night to plant them out until 1-2 weeks ago and they were not happy any more in my 4" pots. Once they were in the ground, most of the plants darkened up within a few days. I cut off pale leaves and these have been replaced by new, dark-green growth.

[nctomatoman]

Lower leaves get ugly (yellow, spotted) when seedings have spent too much time in tight quarters - once they escape and are planted nice and deep in their final location, they typically do fine.