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brooksms
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Purple underneath…too cold?

I've got three types of tomato plants grown from seed in 6" pots under T5 grow lights inside my house. All three of them are a bit purple on the underneath sides of their leaves. One of the plants has a few leaves pointing down toward the soil while the other two do not. I googled and it seems the fluctuation of cooler temperatures may be causing this phosphorus deficiency. Our house is warmer in the daytime and the light bulbs warm the plants. At night, the house is a few degrees colder and the lights are turned off. Other than moving the plants further away from windows at night, is there anything else I can do? They're currently about 1.5 feet from a window but are also right near a vent our heat comes out of.
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Lindsaylew82
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Re: Purple underneath…too cold?

What've you got them growing in? The soil?

Purple in tomatoes leaves is usually caused by a nutrient (phosphorus) deficiency. But you're right about the temp, too. If they're too cold, they can't use the phosphorus in the soil, if it's available. You could place your plants on a heating mat. One that can be adjusted for plants. If it's a temperature issue, one that's resolved, the purple will resolve itself.

They may just need to be fed, though
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imafan26
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Re: Purple underneath…too cold?

Tomatoes are heavy feeders so depending on what you used to start them with and if you added a starter fertilizer, they probably need feeding too. Mine don't usually turn purple until they are much bigger, so cold may also be influencing that. If you are using organic fertilizer and organic media, remember that microbes need to convert the fertilizer to a form usable for the plant to uptake and they don't function as well in the cold. If you are not organic, then start feeding them a water soluble fertilizer to help them grow and warm them up to at least 50 degrees.
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imafan26
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Re: Purple underneath…too cold?

Tomatoes are heavy feeders so depending on what you used to start them with and if you added a starter fertilizer, they probably need feeding too. Mine don't usually turn purple until they are much bigger, so cold may also be influencing that. If you are using organic fertilizer and organic media, remember that microbes need to convert the fertilizer to a form usable for the plant to uptake and they don't function as well in the cold. If you are not organic, then start feeding them a water soluble fertilizer to help them grow and warm them up to at least 50 degrees, but 70 would be even better.
Happy gardening in Hawaii. Gardens are where people grow.

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brooksms
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Re: Purple underneath…too cold?

They are in a mixture of black gold organic potting soil, biomax shrimp compost and worm gold plus castings. I didn't exactly measure so I couldn't tell you a true ratio. The temperature here has really dropped a lot at night this past week so I thought that might be affecting them. Maybe I could set the whole tray elevated over a vent to warm them enough? I don't have a heat mat at home and am trying to save money for installing/filling/irrigating my raised beds. Thanks for your thoughts!

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rainbowgardener
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Re: Purple underneath…too cold?

I think this is quite common in indoor started tomatoes, can be cold, soil, light, etc. Nothing to worry about and they will outgrow it as soon as they go outside.
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applestar
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Re: Purple underneath…too cold?

What are the names of the varieties you are growing?
Tomato plants have different kinds of leaves and this one simply may have different leaf type than others. The one in th picture looks a bit rugose to me.

As stated above a little purple in the leaves is normal for seedlings, and nothing to worry about. Some varieties have intentionally purplish foliage, too.
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brooksms
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Re: Purple underneath…too cold?

applestar wrote:What are the names of the varieties you are growing?
Tomato plants have different kinds of leaves and this one simply may have different leaf type than others. The one in th picture looks a bit rugose to me.

As stated above a little purple in the leaves is normal for seedlings, and nothing to worry about. Some varieties have intentionally purplish foliage, too.
Thanks everyone! I'm glad I can relax about the color. These things are my children right now lol! The pictured one is a yoder's german yellow- https://www.rareseeds.com/yoders-german-yellow-tomato/ I am also growing the tommy toe cherry variety and sioux. The tommy toe seems to be growing the best but I think it just germinated a little bit sooner than the other two. Sioux germinated last so it looks small in comparison.

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brooksms
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Re: Purple underneath…too cold?

Update- I've been keeping an eye on the plant with curled leaves and I think it might have some kind of fungus or disease, but I have zero experience so I'm not sure what happened. Some leaves underneath were wilted. I removed them. Now it seems the a few of the large top leaves have some yellow spots on one side with grayish spots on the other. I've started germinating new seeds to replace this one but I haven't thrown it away yet. Any ideas on what this is?
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applestar
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Re: Purple underneath…too cold?

Don't know abou Yoders but Tommy Toes I'm pretty sure are currant/wild type. I see in your photos leaves with rounded edges which are typical of this type.

I generally don't worry about leaves lower down because they get shed by the plant as it grows or I will bury them when uppotting. If the purple was due to too cold temp, the recovering leaves will look ragged and not as healthy as upper leaves, but I wouldn't worry about them. I do clip off the lower leaves that are touching the ground when they are planted out.

For now, the seedlings need whatever energy production they can get out of their leaves, so I would only clip them off if the damage and stress outweigh the benefit. Stressed plant will be more attractive to pests and diseases.

If the lower leaves are not getting enough light, they will yellow and be aborted by the plants.
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