Tomato seedlings stop growing

kra2012March 25, 2012

I seeded my tomatoes last Sunday 3/18. This past Friday they came up and I moved them under a grow light. Although the stems are turning a redish color and the starter leaves are now a deep green they stopped growing after moving them. This happened last spring as well. I waited four weeks and they didn't grow any further. Eventually I had to purchase already started tomatoes from the local garden store. The temperature is 82 degrees under the light which they get 16 hours of and I'm keeping the soil moist. What do I need to do to get them to grow? Any advice?

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what are they growing in? What kind of mix...

    Bookmark   March 25, 2012 at 4:31PM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

Agree that the two most likely causes is poor growing mix and over-watering. Over-watering is #1 cause. While the reddish/purple stem is normal the "deep green" cotyledons is not. You haven't been feeding them anything have you?


    Bookmark   March 25, 2012 at 4:51PM
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I used Burpee Organic Seed Starting Mix and have not added anything extra. I use a spray bottle to water them every other day and am sure not to soak them. How often should I water them?

    Bookmark   March 25, 2012 at 9:03PM
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Once seeds have sprouted I would lower the temps, maybe twenty degrees lower than your 82. At first I thought the problem might have something to do with the soil as well, but even though I have no experience with your Burpee product I assume it's friable, drains and aerates well enough. As far as watering, if you think that might be part of the problem, do it carefully, waiting for a little dryness on the surface of the medium before watering again. If they're in cells, water them with a small cup so that not just the surface gets a spritz (again, I don't know the particulars here). And no fertilizing at this stage.

Hope you get to the bottom of this. I'm sure it's disappointing.

    Bookmark   March 25, 2012 at 9:13PM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

I use a spray bottle to water them every other day and am sure not to soak them.

Top watering encourages shallow rooting and poor root development. The tap root of the seedling which lies deep in the soil dries out quickly with top watering and growth is stunted.

That is why bottom watering is the standard recommendation they have germinated. You'll find several discussions about this over on the Growing from Seed forum here.

And every other day can still be too much if it isn't needed. There is no set rule to how often to water because it can be affected by many variables. But using the surface soil as an indicator can be very misleading since it is the moisture in the soil down at root level that counts. Checking that moisture level in one of several different ways like using your finger or a Q-tip or piece of tissue on a stick before watering is also a frequent discussion on the G from Seed forum.

But since your plants have not developed true leaves after 4 weeks the odds are that the problem lies with your water method and regimen. True leaves will usually begin to show with 4-6 days after the cotyledons develop.

Hope this helps.


    Bookmark   March 25, 2012 at 10:21PM
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susan2010(6 Massachusetts)

I like and use the Burpee mix with good results, so that's probably not the problem. As for watering, I treat seedlings like other plants, when I water them, I do a thorough/soaking (not drowning) job, discarding any accumulated water in the bottom tray. I do not water again until the seedlings really need it (as I've mentioned before, I use the relative weight of the sixpacks I plant in to judge when they need water). One tip is that if you water well when you plant, you may not need to water again for a week or more. As they grow bigger and develop more roots and leaves, you'll find they need water more frequently. Also, the Burpee mix comes with fertilizer that will carry the seedlings to planting out - you don't need to add more unless you're holding them inside for a lot longer than the normal 6-8 weeks.

Often one of the hardest things for folks new to starting plants from seed to learn is when to let them alone.

    Bookmark   March 26, 2012 at 10:36AM
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