Tomato Seedlings Pale/Yellowing

[z28derick]

Hello everyone,

I saw a recent post about tomato seedlings but didn't quite get an answer for what I thought mine were doing. I've attached pictures of mine and the mix I started with. My seed leaves are turning a pale green, not quite yellow. I'm starting to get a few true leaves on a couple plants but growth seems rather stunted now. I have only been watering every 3-4 days making sure they don't stay too damp. I also have a grow light on them for 12 solid hours, but they also get a good 4 hour shot of direct sunlight from the window (the grow light is still on at that time).

I had assumed the starting mix would have enough nutrients to get me to planting time but everything I'm finding online seems to point to maybe a lack of Nitrogen and Phosphates. I went ahead and added a tiny bit of a fertilizer to two cups last night so I'll keep an eye on those and see if it makes a difference but I wanted to get my pictures on here and see if there were any other suggestions. Thanks!

EDIT: The 4 darker green seedlings on the back left are peppers. Those seem fine so far but they did germinate about a week later.

 

[Chuck]

The actual vegetable seeds have adequate NPK to grow the seedling until the first set of true leaves so I don't think nutrition is the cause of the yellowing. That leaves lighting and temperature. You may have lights that are for plant growth and not seedling growth. From what I can see your plants are just now starting to become leggy as is shown in picture #3. This legginess is caused by insufficient lighting, usually because the plant is too far away from the lights and is reaching or growing toward more light. I would place the lights closer to the plants. A tomato plant or seedling that has purple leaves and stems is suffering from a phosphorus deficiency and the veins of your seedlings are purple. A tomato seedling that has purple stems only is staying a little too cool. Are your plants on a heating mat and is the soil temperature maintaining a constant temperature of about 65F+? IMO the yellowing and slow growth is caused by insufficient lighting and a too cool soil temperature. I would also, just to be on the safe side, fertilize @1/4 rate with an organic liquid fertilizer to all seedlings that do not have at least one set of true leaves. For all other seedlings I would fertilize @1/2 rate.

 

[z28derick]

Thank you for your reply. I'll try moving to light closer. I have had it on it's highest setting. I was beginning to wonder if maybe it was too close. I'll also go ahead and start fertilizing with a small amount. I don't have a heating mat but we do keep the house at 70 during the day, 67 at night. It's odd because last year I had better luck and I didn't have a grow light or fertilize and I thought my seedlings did better. I did start them about 3 weeks earlier this year though hoping to get more of a jump on the season.

 

[Chuck]

Thank you for your reply. I'll try moving to light closer. I have had it on it's highest setting. I was beginning to wonder if maybe it was too close. I'll also go ahead and start fertilizing with a small amount. I don't have a heating mat but we do keep the house at 70 during the day, 67 at night. It's odd because last year I had better luck and I didn't have a grow light or fertilize and I thought my seedlings did better. I did start them about 3 weeks earlier this year though hoping to get more of a jump on the season.

Plants receiving too much light or the light density being too high can cause nutrient disorders and yellowing. I am not at all familiar with your lighting. In lieu of this, I recommend research on your lights before doing anything drastic. And remember that different plants require different light requirements. It seems that most lighting systems use cannabis as the default plant. It appears that your lights are LED. You must determine the distance from the plant the light should be and the wattage of the light determines this. Perhaps someone on this forum knows of a chart or has knowledge that shows this distance.

 

[z28derick]

My lights are indeed LED. I honestly didn't know there was much of a difference between one to another. Perhaps I got the wrong kind https://www.amazon.com/dp/B081CVYZDQ?psc=1&ref=ppx_yo2ov_dt_b_product_details

 

[z28derick]

My lights are indeed LED. I honestly didn't know there was much of a difference between one to another. Perhaps I got the wrong kind https://www.amazon.com/dp/B081CVYZDQ?psc=1&ref=ppx_yo2ov_dt_b_product_details

Reading up on LED grow lights, it sounds like I may have had them too close...

 

[Chuck]

Reading up on LED grow lights, it sounds like I may have had them too close...

It very well could be. Do your research on seedlings and not mature plants as they require different lighting.

 

[z28derick]

It very well could be. Do your research on seedlings and not mature plants as they require different lighting.

Definitely. I just kinda dove in head first with this grow light lol.

 

[z28derick]

I gave them a small dose of food a week ago and also moved the grow light quite a bit higher. Things seem to really be turning around! Most of them have greened back up and started putting on more true leaves. Even the more yellow ones seem to be turning around.