seedling concerns

[dan71314]

I have twenty tomato seedlings under lights in my garage. Most of them have begun to show the first true leaves. They are about four weeks old. My problem is this: some of my seedlings are yellowing on the ends of the cotyledons. I feel like I have been watering them enough and not too much. The soil feels moist throughout and the air temp and soil temp is around 65-70 degrees. I have been reluctant to put the seedlings outside, because here in West Texas, the wind blows on warm days. I was fertilizing with diluted fish emulsion once a week, but the yellowing started when I was fertilizing. I have not fertilized for two weeks. I am new to this "growing from seed" thing. What do I need to do? Could it be that the seedlings are getting too much light under the grow lights? I am using two Grolux lights for aquarium plants and I have them under the light for about 16 hours. Thanks for any help that you all can provide.

[rnewste]

Dan,

Welcome to the Tomatoville Forum. I joined about a year ago, and feel other members have taught me what would have taken 10 years to learn on my own.

I am not experienced enough to comment on the cause and solution to the yellowing issue, but I am certain many other Forum members have this expertise, that they will share with you.

Welcome Aboard!!

Ray

[dice]

My guess would be that they are too moist. They should be
able to grow on just what nutrition is in the seed until they
have at least one set of true leaves, but fish emusion is
generally safe (breaks down slowly enough to not burn seedlings). Sometimes the salt content can be a little high,
but that usually doesn't matter within a single season.
(It can build up in the soil if you use fish emulsion exclusively
year after year in the same place.)

Do you see any of the tips of the true leaves dying? That
is a pretty good indication of too much noisture and not
enough air around the roots. Did you fill the seed-starting
containers loosely or pack the seed-starting mix in there?
You want it loose and airy (that is one reason why people
bottom water seedlings, so that the soil around them does
not get packed down and lose air space).

I would not panic. Just back off on watering and fertilizing,
waiting a few more days after you think you should water.

I doubt that too much light is an issue with that kind of light.

[feldon30]

I get the soil very moist, plant the seeds, and then maybe mist 3-4 days later, and that is the last water I give them until they use it all up and are just about to start wilting (soil surface is noticeably lighter in color). Then I water again probably about once a week. I don't do any fertilization until the second set of true leaves.

[dan71314]

Thank you all for the advice. I guess I can get a little carried away with the nuturing. This is such a great forum!!!

[akgardengirl]

My seedlings did the same thing except the whole cotyledon turned yellow and some have dropped off. No difference in planting from other years. I used the ABS system with Jiffy starting mix. I also noticed some little black flies hanging on the stems. They're squished now.
Sue

[Ruth_10]

My guess would be too much moisture. I use the weight method for determining when they should get more water--when I lift them and they feel light it's time for water. You'd be surprised at how quickly you get a feel for just how much water is present using that method.