Young purple seedlings

I've had these tomato seedlings under lights and on heat mats for 4 weeks.
They are all really purple.
Are they nutrient deficient?
They look reasonably healthy to me apart from the color.
They are only just getting there first true leaves, should I hold off and wait untill they are more developed to fertilize.
I used organic store bought seedling mix.
Thanks,
James

Maybe phosphorous deficient? That can cause red/purple color. But it may also just be the variety.

Thom Bri wrote:Maybe phosphorous deficient? That can cause red/purple color. But it may also just be the variety.

Phosphorus deficient, that's what I'm thinking but can't understand why.
And is it too early to fertilize, They only just got their true leaves?
Would it be better to just re-pot them early into a mix of potting soil and compost?
It's across multiple varieties so don't think it's that.

Thom Bri wrote:Maybe phosphorous deficient? That can cause red/purple color. But it may also just be the variety.

Purpling of leaves in seedlings is a general sign of stress in tomato seedlings, and can be caused by a few different things. Apart from phosphorous, it could also be: too cold (nighttime lows should be over 14C/58F -- and a heat mat only protects the roots), to wet, or grow lights not providing the right lighting for the plants.

What to do about it? You may not need to do anything. I have this problem every year as I start my tomatoes in an unheated glasshouse or on a cold windowsill. Once they're a bit bigger and in the ground, they've always come right for me. That being said, making sure they're not getting to chilled at night will help them grow better regardless!

Seed compost normally doesn't have much in the way of nutrients, so if you have time/space I would pot on any that have true leaves. As M Broussard says, they'll survive and grow on regardless.
I found that some of my tomato seedling purpling was due to overwatering. At least, when I monitored the watering and only watered when the compost underneath was dry the seedlings did do better. Starving my seedlings was certainly part of it too, and I keep meaning to plant fewer and pot them on sooner.....

What variety were those seedlings?

Some seedlings can be purple due to variety.

I'm going to add my vote for stressed... and temperature is the most common one I run into. If I put the plants out a little too early, or if the seedlings get a little too cold, they turn purple. Once they get in the ground and warmed up for a while they go back to green just fine. Maybe there is a slight delay in their growth, but not noticeable.

I have had tomatoes that looked like that before and they were badly deficient in phosphorus.  I sprinkled some bone meal over them and watered it in and the purple leaves turned green in no time!  My thoughts for you are

1)  sprinkle some bone meal over the seedlings and water in

2)  make sure that wherever they eventually go that they have a good access to plenty of phosphorus.  Again, I would use bone meal by working it into the ground/bedding near where you plant

Bone meal has long been one of my favorite soil amendments.  Prior to discovering wood chips and mushrooms, whenever I planted tomatoes I always mixes a combination of bone meal and blood meal into the soil to add a good dose of phosphorus and nitrogen to the hungry tomato plants.

Good luck,

Eric

I have to admit I've stopped using store bought seedling mix in favour of my own mix with my mature compost. As a Chicken/duck wrangler, I end up with a lot of bones in my compost and biocharred bones as well.  

So I vote for potting some of them up in real soil along with some extra goodies and see how it goes.

Thanks for all the info, much appreciated.
It could be cold, their in a unheated room on heat mats. It hasn't being particularly cold lately though.

It could also be over watering. I recently added fans and that changed the amount of water they needed. I lost a few because I let them dry out a bit so maybe I over compensated and watered too much.

They are in a cold frame under real sun now that doesn't get below 60° at night so hopefully they can balance out.
Could that also be a stress factor. Moving from under lights to out in real sun?

I think I'm going to leave them for another couple of days in the cold frame before potting up to monitor the situation.

Anne Miller wrote:What variety were those seedlings?

Some seedlings can be purple due to variety.

It's a mix of different varieties. Better boy, super sweet 100's, sun Sugers, black Cherry's (could be naturally purple), pineapple, Cherokee purple Arkansas traveller. Maybe one or two more

Jay Angler wrote:I have to admit I've stopped using store bought seedling mix in favour of my own mix with my mature compost. As a Chicken/duck wrangler, I end up with a lot of bones in my compost and biocharred bones as well.  

So I vote for potting some of them up in real soil along with some extra goodies and see how it goes.

I am making my own now with coconut coir, perlite, vermiculite and a handful of work castings. That's what I start the seeds in.
I've got some well broken down compost mostly consisting of cow manure. When I pot them up I was going to do 1:1 with the coconut coir and compost and add enough perlite and vermiculite to get the consistency right.
Does this sound about right to you?

James Hird wrote: When I pot them up I was going to do 1:1 with the coconut coir and compost and add enough perlite and vermiculite to get the consistency right. Does this sound about right to you?

How large a pot? This seems heavy on the coir. I don't think I ever use more than 1/4 soaked coir, but if the pot's really small, you might need more to help reduce how quickly they dry out.  I have also started adding some actual dirt to my mix. Dirt has things in it - particularly minerals - that I'm not convinced pure organic matter has.

Jay Angler wrote:

James Hird wrote: When I pot them up I was going to do 1:1 with the coconut coir and compost and add enough perlite and vermiculite to get the consistency right. Does this sound about right to you?

How large a pot? This seems heavy on the coir. I don't think I ever use more than 1/4 soaked coir, but if the pot's really small, you might need more to help reduce how quickly they dry out.  I have also started adding some actual dirt to my mix. Dirt has things in it - particularly minerals - that I'm not convinced pure organic matter has.

Funny you should say that. I've being thinking about adding some of my top soil to the mix. It's really sandy 1:1:1 soil, compost, coir plus the perlite and vermiculite.
I'm potting into 4" round pots
The soil I'd be adding is the same soil that it will finally be going into so I was thinking it would be adjusting the plant to it.

I might do a couple different mixes and see if there is much difference.

James Hird wrote: I might do a couple different mixes and see if there is much difference.

That's the spirit! Please take before and after pictures. Since some of the seedlings seem to be struggling more than others, I would try both the stronger and the weaker ones in different recipes and see what happens.

That said, I don't like to see babies die... so crushing up some bones from your dinners or from the neighbour's dinners, seems like a good idea for some extra phosphorus. However, an easier source which I use is dried, crushed egg shells. I put a spoonful in the bottom of my pots and let the microorganisms spread the goodness where needed.

If you're on sandy soil, I have read that biochar can be a big help, as it helps to hold onto nutrients.

Jay Angler wrote:

James Hird wrote: I might do a couple different mixes and see if there is much difference.

That's the spirit! Please take before and after pictures. Since some of the seedlings seem to be struggling more than others, I would try both the stronger and the weaker ones in different recipes and see what happens.

That said, I don't like to see babies die... so crushing up some bones from your dinners or from the neighbour's dinners, seems like a good idea for some extra phosphorus. However, an easier source which I use is dried, crushed egg shells. I put a spoonful in the bottom of my pots and let the microorganisms spread the goodness where needed.

If you're on sandy soil, I have read that biochar can be a big help, as it helps to hold onto nutrients.

I heat my house over winter with a log burning stove so I mix all that ash in with my compost. I know it's not as good as bio-char but there are some chunks of charcoal in it. Good for potassium too.

A little update. The seedlings seem to be doing better, still very purple but new leaves are green. I think it was a combination of over watering and then shock from being moved outside too quickly.
I'm going to have a potting up session this evening so will take lots of photos. I'll make a separate post. Kind of like a mini case study.
I've lost a fair few seedings already but for my first year doing this I've learnt a hell of a lot. Still plenty to learn too of course.

Jay Angler wrote:

James Hird wrote: I might do a couple different mixes and see if there is much difference.

That's the spirit! Please take before and after pictures. Since some of the seedlings seem to be struggling more than others, I would try both the stronger and the weaker ones in different recipes and see what happens.

That said, I don't like to see babies die... so crushing up some bones from your dinners or from the neighbour's dinners, seems like a good idea for some extra phosphorus. However, an easier source which I use is dried, crushed egg shells. I put a spoonful in the bottom of my pots and let the microorganisms spread the goodness where needed.

If you're on sandy soil, I have read that biochar can be a big help, as it helps to hold onto nutrients.

Do you think seedlings with only one small true leaf are too small to pot up? I know it's not recommend but in this case I'm thinking of risking it. I potted up 5 or 6 a few days ago as a test and they are all doing much better in their new pots. I did only pot up seedling with 2 true leaves though

James Hird wrote:I heat my house over winter with a log burning stove so I mix all that ash in with my compost. I know it's not as good as bio-char but there are some chunks of charcoal in it. Good for potassium too.

Depending on how wet your compost gets, this could be part of your problem. Tomatoes like acidic soil, and ash pushes things basic. I added a bit too much ash one year, and my tomato starts were truly unhappy. When I mixed new soil with only the tinyest bit of ash, tomato plants were happy. Can you test the acidity of your soil?

and wrote:

Do you think seedlings with only one small true leaf are too small to pot up?

If they're looking unhappy, and not growing well, I'd take the chance if it were me. Just be as gentle with them as you can be!

Jay Angler wrote:

James Hird wrote:I heat my house over winter with a log burning stove so I mix all that ash in with my compost. I know it's not as good as bio-char but there are some chunks of charcoal in it. Good for potassium too.

Depending on how wet your compost gets, this could be part of your problem. Tomatoes like acidic soil, and ash pushes things basic. I added a bit too much ash one year, and my tomato starts were truly unhappy. When I mixed new soil with only the tinyest bit of ash, tomato plants were happy. Can you test the acidity of your soil?

and wrote:

Do you think seedlings with only one small true leaf are too small to pot up?

If they're looking unhappy, and not growing well, I'd take the chance if it were me. Just be as gentle with them as you can be!

I've got litmus paper, I'll test my compost and soil.
It was store bought organic seedling mix they were planted in though. I'm not happy with it, it wasn't cheap and I noticed a improvement in other seedlings when I started making my own.
I repotted most of them last night. I'm pretty sure it was over watering that did it. I noticed the stems at soil level was pale colored and shriveled on quite a few of them. Some wern't able to hold there own weight.
When I repotted I buried them as deep as I could so they can grow new roots from the stem hairs and to support them a little.
I'm going to make a post about it now.
Thanks for all your help and info