Seedlings turning colors despite fertilize.
Posted: Sat Mar 30, 2024 7:22 pm
My tomato seedlings are turning either yellow or purple despite watering weekly with diluted Schultz's 20-20-20 plant food. What am I doing wrong???
Welcome to the Friendliest Gardening Forum, Let's grow together!!!
https://www.tomatojunction.com/
Seedlings turning colors despite fertilize.
Page 1 of 1
Re: Seedlings turning colors despite fertilize.
Posted: Sat Mar 30, 2024 8:15 pm
What variety? I'm asking because some varieties have darker seedlings.
Re: Seedlings turning colors despite fertilize.
Posted: Sat Mar 30, 2024 8:26 pm
Re: Seedlings turning colors despite fertilize.
Posted: Sat Mar 30, 2024 8:29 pm
I wouldn't worry about it too much. They will normalize once you get them outside. It could be the variety. I could be the temperature. Cooler temps slow absorption of nutrients down. Low phosphorous can make them appear purple. They look healthy and as long as they are disease free, they will be fine.
Re: Seedlings turning colors despite fertilize.
Posted: Sat Mar 30, 2024 9:22 pm
Thanks! 
Re: Seedlings turning colors despite fertilize.
Posted: Sat Mar 30, 2024 10:47 pm
My first thought by looking at them is sulfur-deficiency.
Re: Seedlings turning colors despite fertilize.
Posted: Sun Mar 31, 2024 12:00 am
I use just calcium nitrate at seedling stage. They don't need hardly any p and k at all, and those two elements can also build up in your media, which can rot roots and also block other nutrients from being absorbed.
Re: Seedlings turning colors despite fertilize.
Posted: Sun Mar 31, 2024 12:28 am
Purple leaves at the seedling stage would be a sign of phosphorus deficiency in the plant, not potassium. Maybe that's what you meant; I often type one of those when I mean the other, not sure why. Potassium deficiency looks different from what your seedlings are showing.TomatoNut95 wrote: ↑Sat Mar 30, 2024 8:26 pmZimmertomate Blau microdwarf. Yes I know plants that produce black fruits have darker foliage but this is a potassium deficiency. I can tell.
If your seedlings do have a phosphorus deficiency, it's probably not because there's too little phosphorous in the soil. More likely it would be that your growing area is colder than ideal, or the soil is too wet. It also seems like certain types of lights may contribute to the problem. My point being, don't try to fix it by increasing the fertilizer.
I don't think you should discount the fact of this being a dark antho tomato. I googled pictures of this variety because I wasn't familiar with it, and there are lots of images with very dark purple on the leaves. This may be normal for this variety at the seedling stage. Your plants look very healthy other than the unusual coloring, so it doesn't really seem like a nutrient deficiency.
If you do think there's something wrong with the seedlings, my suggestions would be get them some natural light (gradually) and back off the fertilizing a bit. But I agree with @MissS that most likely no action is needed and they'll do well once they're planted.
Re: Seedlings turning colors despite fertilize.
Posted: Sun Mar 31, 2024 12:24 pm
From growing a lot of micros I wouldn’t worry to much they are at least for me very strong plants that can take a lot.. I had a bunch last year that looked like that and they were just fine. Some are just darker than others..
Re: Seedlings turning colors despite fertilize.
Posted: Sun Mar 31, 2024 12:58 pm
Purple possible cool weather causing phosphorus deficiency and the lighter color in the middle of the tops is new growth.
(((Possibly.)))
(((Possibly.)))
Re: Seedlings turning colors despite fertilize.
Posted: Sun Mar 31, 2024 3:17 pm
I concur, like any other issue, until you know what a healthy plant is supposed to look like, it’s hard to know if there is an issue.
Seven Bends wrote: ↑Sun Mar 31, 2024 12:28 amPurple leaves at the seedling stage would be a sign of phosphorus deficiency in the plant, not potassium. Maybe that's what you meant; I often type one of those when I mean the other, not sure why. Potassium deficiency looks different from what your seedlings are showing.TomatoNut95 wrote: ↑Sat Mar 30, 2024 8:26 pmZimmertomate Blau microdwarf. Yes I know plants that produce black fruits have darker foliage but this is a potassium deficiency. I can tell.
If your seedlings do have a phosphorus deficiency, it's probably not because there's too little phosphorous in the soil. More likely it would be that your growing area is colder than ideal, or the soil is too wet. It also seems like certain types of lights may contribute to the problem. My point being, don't try to fix it by increasing the fertilizer.
I don't think you should discount the fact of this being a dark antho tomato. I googled pictures of this variety because I wasn't familiar with it, and there are lots of images with very dark purple on the leaves. This may be normal for this variety at the seedling stage. Your plants look very healthy other than the unusual coloring, so it doesn't really seem like a nutrient deficiency.
If you do think there's something wrong with the seedlings, my suggestions would be get them some natural light (gradually) and back off the fertilizing a bit. But I agree with @MissS that most likely no action is needed and they'll do well once they're planted.
Re: Seedlings turning colors despite fertilize.
Posted: Sun Mar 31, 2024 4:55 pm
Thanks everyone for the advice; I'm anxious to get everything planted out and can hopefully work on that this week! 
Re: Seedlings turning colors despite fertilize.
Posted: Wed Apr 03, 2024 6:59 pm
You're not doing anything wrong!
Many tomatoes do this under grow lights, particularly under lights with lots of blue (cooler/higher kelvins). This is actually how commercial greenhouses induce purple leaves in ornamental plants. Some tomato varieties are more susceptible than others. This year, 7 of the 11 tomatoes I grew had purple leaves like that. There's nothing wrong with them. They go back to green after a few days in the sun. Unless they're dark antho varieties, in which case the leaves are supposed to be purpley to some degree.
Like others have said, purple leaves can also be caused by poor phosphorus uptake. Like @Seven Bends said, don't increase fertilizer. You'd rule out uptake issues by doing things you need to do anyways for healthy tomato plants. Make sure:
-Temps aren't too cold
-The seedlings aren't rootbound
-You're not overwatering
Many tomatoes do this under grow lights, particularly under lights with lots of blue (cooler/higher kelvins). This is actually how commercial greenhouses induce purple leaves in ornamental plants. Some tomato varieties are more susceptible than others. This year, 7 of the 11 tomatoes I grew had purple leaves like that. There's nothing wrong with them. They go back to green after a few days in the sun. Unless they're dark antho varieties, in which case the leaves are supposed to be purpley to some degree.
Like others have said, purple leaves can also be caused by poor phosphorus uptake. Like @Seven Bends said, don't increase fertilizer. You'd rule out uptake issues by doing things you need to do anyways for healthy tomato plants. Make sure:
-Temps aren't too cold
-The seedlings aren't rootbound
-You're not overwatering
Re: Seedlings turning colors despite fertilize.
Posted: Wed Apr 03, 2024 7:05 pm
Thanks everyone, I'll let y'all know how they do! After this horrendous wind has died down after 3 rough days of it, I'll get more transplanted outside.