Discoloration on tomato seedling leaves - Ask Extension
Hi. We planted San Marzano, beefsteak, and cherry tomatoes a few weeks ago and recently up potted them into Solo cups. A couple days after up potting,...
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Discoloration on tomato seedling leaves #867083
Asked May 05, 2024, 10:40 AM EDT
Hi. We planted San Marzano, beefsteak, and cherry tomatoes a few weeks ago and recently up potted them into Solo cups. A couple days after up potting, I noticed the leaves on many San Marzano and beefsteak plants are turning yellow and/or purple, and spots are appearing on some of the leaves. Also, some of the leaves are curling and some of the stems are bending. The plants don’t seem to be growing. To up pot them, I used a potting mix with fertilizer in it and I also lightly fertilized with a 2–2–2 liquid a day or two after up potting. We have kept the grow lights between 2 and 4 inches at all times. We have been a little inconsistent with watering – after up potting the soil seemed heavy and I didn’t water for a couple of days and then perhaps overcompensated by watering too much. Can you tell me why the leaves are turning these colors and getting spots? Are they missing nutrients? A watering problem? A disease? Thanks for your help!
Baltimore County Maryland
Expert Response
I have to say that your plants actually look like they are doing pretty well. The potting mix looks a little heavy it shouldn't really be that much of a problem. Maybe it is time to start hardening them off by taking them outdoors in the daytime and placing them in a shaded area. If you still keep them inside though, be sure the lights are on for 14-16 hours a day.
Take a look at this link which will give you a lot of information on starting seeds, proper growing media, and the hardening process. Maybe there will be some details that would be helpful the next time you do this.
https://extension.umd.edu/resource/starting-seeds-indoors/
I am hoping you will grow some amazing tomatoes this summer! Robin
Take a look at this link which will give you a lot of information on starting seeds, proper growing media, and the hardening process. Maybe there will be some details that would be helpful the next time you do this.
https://extension.umd.edu/resource/starting-seeds-indoors/
I am hoping you will grow some amazing tomatoes this summer! Robin
Thank you for the assurance and resources, Robin! I'm a first-time indoor seedling parent (could you tell?) and am a little anxious. After some more observation I realize it's mostly the big beefsteak tomato plants that are exhibiting leaf curl, turning purple, and showing some spots. I'm attaching some more photos that seem to me to show more distress. Thanks for any suggestions you can give.
As Robin mentioned, the seedlings don't look super stressed, but they would benefit from starting to acclimate to outdoor conditions so they can go into the ground soon (or into containers if that is the plan). Put them out an increasing number of hours each day, starting in the shade, to get them used to the brighter light, humidity and temperature fluctuation, and better airflow. Liquid fertilizers tend to be absorbed faster than time-release types used in potting mixes; this is not a problem, just a reason why some nutrients will take more time to be available to the plant. As the plants get exposed to warmth and more light while outside, they should begin to produce more growth. Young plants can seem to be slow-growing at first, since they are developing lots of roots at the same time foliage is being produced.
We presume the solo cups have at least one drainage hole in the bottom? If not, it may be easier to over-water. Don't keep the soil evenly damp...let it get a little dry to the touch in the top inch(-ish) between waterings, especially as the seedlings grow older.
Miri
We presume the solo cups have at least one drainage hole in the bottom? If not, it may be easier to over-water. Don't keep the soil evenly damp...let it get a little dry to the touch in the top inch(-ish) between waterings, especially as the seedlings grow older.
Miri
Thanks, Miri! This is so helpful. I've started putting them outdoors the last two days. I thought at first they were too young/small to go out (I seeded kind of late) so it's good to know that they can take it. It makes sense that they'll begin to show more growth outside.
Yes, the solo cups have two holes each, a little smaller than a pencil eraser.
Thanks again! I really appreciate the advice and information.
You're welcome!
