Seedlings unhealthy

Asked April 23, 2020, 11:14 AM EDT

Hello, I started seedlings, some as many as 6 weeks ago— kale, broccoli, tomatoes, peppers, and others. They have come up okay and grow their first two real leaves and then they start to look bad and stop growing. Some leaves are mottled shades of green, some have started to turn purple/red and now I’ve noticed that some of the soil has started to have what looks like white and sometimes green mold. I water daily and have been applying a diluted fish fertilizer around every week and more recently. They are very closely under an LED shop light with a fan on them. The temp in the house is between 60 and 68 usually. I tended these so carefully and I’m discouraged. Should I throw them away and try again? If so, how do I stop this from happening again? Do I try to rescue them? I’m worried that they have a fungus/blight and don’t want to put them in my garden if it’s something that could spread. I grew some peas in the house that did get a powdery mildew and I ended up tossing those. Pictures attached of current seedlings.

Ingham County Michigan

7 Responses

Thanks for your question. First thing is to not be discouraged. All gardeners have problems and failures. The yellowing in the first picture may be from over watering. The powdery mildew would indicate high humidity. This seems to fit with the moldy soil. You may have to kick the fan up a little to get more air circulation; however, you would need to make sure the plants don't dry up. The purple is usually associated with cool temperatures which can inhibit phosphorous uptake. Solanaceous plants really don't like cool temperatures. Even with all that, something else may be off. The "diluted fish emulsion" is probably not needed in the first 4 to 6 weeks. The dilution should be less than suggested on the label of the fish emulsion. Another concern would be the growing media. A sterile soilless mix works best and not all mixes are equal. If fertilizer is in the mix, the fish emulsion would not be required. Sanitation is also important pots, trays, tool, etc should be clean and disinfected so not to spread disease. Since some diseases are seed borne it is suggested to not use saved seeds. I think it would be a good exercise to work with these seedlings. You could grow some more for backup. Pl;ease let us know if you have additional questions. Check out the following links:
https://extension.umn.edu/planting-and-growing-guides/starting-seeds-indoors#soilless-seed-starting-mixtures-1178963
https://extension.unh.edu/resource/starting-plants-seed-fact-sheet
I hope this is helpful,

Thank you for your response. I haven’t given up on them, at least not all of them. I reported into bigger pots, watered them less and stopped using the fertilizer hoping things would improve. Some of the plants have grown to the point where I want to put them in the garden BUT they still look unhealthy— the Brussel sprouts and broccoli specifically. Pictures attached.

If I put them in the garden am I risking infecting my other plants with something, such as downy mildew? I clearly had downy mildew in some of my seedlings that I threw away and wonder if this is what is also afflicting the remaining... If so, are there ways to treat it or prevent spread? What would you suggest?

thanks again for your time! Much appreciated!




The yellowing of the leaves is most likely the remnant of too much water. As new leaves develop they should probably look okay. One thing that we had not reviewed was your LED lamp. Good light is essential in growing transplant. Low light especially in the red or blue spectrum can create some yellowing. I am concerned with your "downy mildew". Downy mildew is a very serious problem; however, powdery mildew is less so. We want to be sure of the disease. It may not hurt to use a fungicide (listed for vegetables) on your plants after they settle in outside. If you have an infected leaf send a picture of the front and back side of the leaf to see if we can determine the problem. I hope the plants come around for you.

I was using powdery and downy mildew interchangeably and it was a beginners self diagnosis— so I really don’t know what’s going on. I’ve gotten rid of most of the plants that looked bad. Attached are pictures of a few leaves that I took from healthy-ish looking plants. You’ll see that one leaf totally dried out on the plant and the back looks kind of grey and possibly fuzzy. Then there is the half yellow/red leaf that looks like it may have two white patches on the back but they are so small it’s hard to tell.

regarding the LED light, that could also be a problem. The ones I have are 4,000k which appear to be in the yellow range.

The photo's don't give enough detail to be sure. Clip off any leaves that have declined and use a fungicide as previously proposed. It is always good to clean you cutting tool with rubbing alcohol between cuts to prevent spreading diseases. The light temp is okay, perhaps the intensity is a little low. Don't forget to harden the plants off before planting outside. That way they can adjust to the bright sun and outdoor breezes. Let's hope things are on the right track.

Does this picture tell you anything? This is a leaf from my healthiest looking kale plant— the bottom leaf was dropping and starting to turn yellow

This may be downy mildew if as you indicated that backside was fuzzy grayish/whitish. Downy Mildew is a "water mold" which is different than a fungus. Take a look at the following link for details and controls:
https://www.extension.purdue.edu/extmedia/BP/BP-68-W.pdf