Yellow Leaves - Seedlings

15 years ago

I've been starting heirlooms from seed for a few years now with great results. I use a vermicompost/peat mixture under flourescent lights. I have been hardening off the past week and then bringing them in at night to put under lights again. I have plants that I am giving away that I don't give light to at night and they have no signs of yellowing. Did I answer my own question? Do I need to give them a break from so much light? When I transplanted last week I watered pretty heavy and then let the soil get pretty dry before watering again. It appears to me that the ones with sunlight and flourescent during the night have the yellowing leaves; although they are in the same tray as the peppers and they are doing great. Comments please?

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Comments (4)

Bets
15 years ago
Most literature (even online) about tomato seedlings recommend 14-18 hours of light with a rest period, although many growers have said they have lights on them 24 x 7 with no adverse effects, so that is not likely to be the issue.

Yellowing leaves on seedlings is a classic symptom of overwatering. Salt Damage can also cause leaves to yellow, are you in an area with hard water? Do you notice any "mineral" build up in your pots? Iron defficiency can also cause yellowing of leaves, but by far the biggest culprit is over watering or poor drainage.

I'd suggest two things: First - check the moisture near the bottom of the containers. (Try a small wooden dowel or skewer, put it in and leave it for a bit then pull it out. Is it wet? Cut back on watering. If dry, then they need water. Just damp, they are fine.)

Second - give the plants at least 6 hours of darkness.

I hope that helps.

Betsy
eric30
Original Author
15 years ago
Thanks Betsy. Learn something everyday. I have hard water but haven't noticed any mineral residue on anything. The seedlings came up strong for the 1st 5 weeks. This just happened recently when I transplanted from small cells into my homemade paper pots. I must admit I did water a little too heavy after transplanting. my peat/vermicompost mixture slurps water right up and it took 4 days to get them to dry out, even out in the breeze. I was more carefull with the segregated plants that I am handing out to friends because they are in much smaller flats. Last night I brought them back inside and left the lights off.
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ethnobotany
15 years ago
If the watering doesn't help, it could be nitrogen deficiency. Although, with a good vermicompost component in the mixture, I don't know why a nitrogen deficiency would be the case. Just an alternative opinion though.
eric30
Original Author
15 years ago
I think I figured out what I did. When I transplanted from cells to newspaper pots, I left alot of air gaps around the root ball. A result of being greedy with space and didn't allow enough room between the root ball and paper pot to compact potting mix around. When I went to plant into the garden, the exposed roots were turning yellow and suffering. Now all of the plants are growing green tops. Maybe the stress made them tougher.