Help with tomato seedlings??

[swadloony]

I'm starting my first garden this year and have been growing some tomato plants from seed indoors. They seem to have gotten off to a good start, but yesterday I noticed that a few of the plants have leaves that are developing a mottled yellowish look, with dark green spots.

I've got no idea what to do about this, but I'm panicking just slightly because I lost my entire first attempt at pepper seedlings due to damping off, and I don't want my tomatoes to die as well. Has anybody ever seen this before?

A couple things to note: I've been keeping the seedlings under a grow light for about 14 hours a day. I took them off the heating mat once they germinated. I water them roughly every other day, and have just started adding diluted liquid fertilizer once a week to their water (3-1-2 mixture). The ambient room temperature is around 67 degrees but it's a least a couple degrees warmer under the light. I've also started taking them outside for a little bit every day. All of the tomato plants seem to be pretty sturdy, although their stems and the undersides of their leaves are dark purple and I've read that this can possibly be signs of a nutrient deficiency.

If anybody can see anything I'm obviously doing wrong, or has ever experienced seedlings that look like this and knows how to fix it, please let me know!

 

[Chuck]

Your plants are definitely suffering from a phosphorus deficiency. For this add bonemeal. It also appears that they may be under an LED light that is not proper for seedlings or is under the light for too long a time. What is the soil made of? It appears to be either peat or coir and if it is peat this substance ties up P and makes it unavailable to plants. Change the growing medium if so. Those spots are a fungus but I think the plant will recover if you foliar spray with Neem Oil. I would also sprinkle a big tablespoon of epsom salts around the base of the seedlings and water it in. If your outdoor ambient temperature is 55F+ leave them outside during daylight hours out of the wind.

 

[swadloony]

Your plants are definitely suffering from a phosphorus deficiency. For this add bonemeal. It also appears that they may be under an LED light that is not proper for seedlings or is under the light for too long a time. What is the soil made of? It appears to be either peat or coir and if it is peat this substance ties up P and makes it unavailable to plants. Change the growing medium if so. Those spots are a fungus but I think the plant will recover if you foliar spray with Neem Oil. I would also sprinkle a big tablespoon of epsom salts around the base of the seedlings and water it in. If your outdoor ambient temperature is 55F+ leave them outside during daylight hours out of the wind.

Thank you so much for these tips! The lights I bought are LED but they're specifically made to be grow lights so I assumed they are safe. I could try reducing the time I leave them on and see if that makes any difference.

The seed starting mix I bought is a mixture of peat, coir, and vermiculite. If I were to buy something else and transplant, what would I want to look for?

And I do have a bag of organic fertilizer that includes like bone meal and other types of meal, but I was under the impression this type of fertilizer is only safe to use after the plants are larger. Apparently that's not true.

Thanks again!

 

[Chuck]

Peat has zero nutritional value. About all it does is retain moisture it retains or holds onto the nutrients in fertilizers thus not allowing it to get washed away. Coir on the other hand has quite a few nutrients. Potting mixes are a combination of composted materials with usually some peat added and sometimes trace minerals and/or manures. Vermiculite also has zero nutrients. All it does is retain moisture and nutrients like the peat. I would get the most expensive potting mix you can afford as one usually gets what one pays for. I would start using your organic fertilizer whether it be in a powdered or granular form, but, at 1/2 the rate until you have 2 complete sets of true leaves. It is possible to damage young tender seedlings with too much organic fertilizer but when a plant gets 3 sets of true leaves this is not the case.

 

[Oliver Buckle]

When I pot on my seedlings I use a mix of 3 parts top soil, 2 parts compost and 2 parts manure. It's purely arbitrary, what I 'felt' was right, but it seems to work. When I plant out I put a mixture of one part of each into the planting hole, a bit stronger on the manure.

 

[swadloony]

Peat has zero nutritional value. About all it does is retain moisture it retains or holds onto the nutrients in fertilizers thus not allowing it to get washed away. Coir on the other hand has quite a few nutrients. Potting mixes are a combination of composted materials with usually some peat added and sometimes trace minerals and/or manures. Vermiculite also has zero nutrients. All it does is retain moisture and nutrients like the peat. I would get the most expensive potting mix you can afford as one usually gets what one pays for. I would start using your organic fertilizer whether it be in a powdered or granular form, but, at 1/2 the rate until you have 2 complete sets of true leaves. It is possible to damage young tender seedlings with too much organic fertilizer but when a plant gets 3 sets of true leaves this is not the case.

Super good info, thank you! I just ordered some new potting mix that seems to be highly rated so hopefully it will get here in time to save my tomatoes. And in the meantime I'll figure out the right amount of that fertilizer to add.

 

[swadloony]

When I pot on my seedlings I use a mix of 3 parts top soil, 2 parts compost and 2 parts manure. It's purely arbitrary, what I 'felt' was right, but it seems to work. When I plant out I put a mixture of one part of each into the planting hole, a bit stronger on the manure.

Noted for the future, thanks! I'll definitely be adding some of that stuff when I transplant my seedlings outside.