Should I turn off the heat mat?

misterpatrick(4)March 19, 2012

Hello all,

started a tray of seeds last Thursday. I'd say half of them are up and some (the pineapple tomato especially) are almost already 1.5" high. That's a bit leggy so I'm wondering if I should turn the heat mat off and remove the dome. I'm thinking that the rest of the seeds have probably germinated but haven't popped out yet. Here's a photo:

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srjohnt(6)

It's probably not the heat mat, but rather that your light source isn't close enough to the plants. I can't see your lights, but they should be right down on the plants, about 2 inches from the plant leaves.

If that's a window in the background, and that's the light source, they're gonna get a lot worse.

    Bookmark   March 19, 2012 at 7:53PM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

And yes you should turn off the heat mat. And dome should definitely already be off. The rest will germinate shortly without either or they never would have germinated anyway.

Dave

    Bookmark   March 19, 2012 at 9:19PM
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misterpatrick(4)

Thanks for the tips! I actually do have lights - four T-12's on chains above each rack of trays which I generally keep a few inches above the seedlings. Those seedlings really jumped up. They just sprouted yesterday and today a few of them are that tall. I'm leaving town for a week and a half. So hopefully my wife will keep an eye on them and keep them nicely bottom-watered.

I'll post updates as the seedlings progress. The test seedlings I started a few months back are about a foot high now and all have many blossoms and several fruits.

    Bookmark   March 20, 2012 at 1:08AM
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capoman(5a)

Get rid of the dome for sure or you'll get damp off. You didn't say the soil temperature. If you have a cool room, it doesn't hurt to leave a controlled heat mat keeping soil temperature near normal room temperature. If the soil is too cold then you will need to water less which is not good for the roots. Having to water more often adds more air to the roots. Also, I am not a fan of bottom watering. Once the plants are up, I would top water seedling trays with a baster or something similar. Do not let them sit in water.

    Bookmark   March 20, 2012 at 9:49AM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

If you have a cool room, it doesn't hurt to leave a controlled heat mat keeping soil temperature near normal room temperature. If the soil is too cold then you will need to water less which is not good for the roots. Having to water more often adds more air to the roots. Also, I am not a fan of bottom watering. Once the plants are up, I would top water seedling trays with a baster or something similar.

While I am glad all that works for you it certainly goes against all the standard growing from seed info. Cool growing conditions, once germinated, is much better than warmth and a heat mat under germinated seedlings can quickly cook the tiny roots. Adding water deprives the roots of air rather than adding it. Bottom watering does NOT mean letting the plants sit in water.

Dave

    Bookmark   March 20, 2012 at 10:49AM
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missingtheobvious(Blue Ridge 7a)

Bottom-watering has the advantage of not splashing the potting mix off the seeds/tiniest seedlings. It also assures the mix absorbs enough water.

Leave the seedlings in the water for 20-30 minutes, then remove them and pour off the water. The roots will not lack air. [It helps if your tray system includes a tray with a mesh bottom, which makes it quicker and easier to move the seedlings into and then out of the solid bottom tray for watering. The exact amount of time you leave the tray sitting in water will depend on how often you water and on the makeup of the starting/potting mix.]

Mist the top of the soil as needed, particularly before germination is complete. I'm fond of these watering roses, which you just attach to a small plastic bottle (I think they don't work on Coke bottles or the new Pepsi bottles):
http://www.backyardgardener.com/seeds/product08/m2081.html

    Bookmark   March 20, 2012 at 11:13AM
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capoman(5a)

A couple of rebuttals. First, about the heat, if you have an uncontrolled heat mat, I agree you are best without it. But if can control heat by using a controller that measures soil temperature so that you go no higher then standard room temperature, your plants will love it. Then there's peppers, which LOVE warm roots at any stage.

As far as watering, it's best to use a well drained soil mix, even for seedlings. With a well drained soil, you are best off off watering from the top, but using something like a baster to avoid splashing the seedlings and throwing up soil. I agree that a mesh on bottom is best to prevent sitting in water. The movement of water from top and draining out the bottom will draw fresh air into the root zone. Watering from the bottom will only push air out and tends to saturate soil.

Of course if you are using crappy water retentive soil like MG seedling soil, that may not apply, but I would hope gardeners doing their research on this site would already know the benefits of using fast well draining soil less mixes, even for seedlings.

    Bookmark   March 20, 2012 at 1:55PM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

Actually I find that peppers much prefer cooler roots as seedlings. We intentionally keep then at the ambient temp of 60-65 degrees in the greenhouse to avoid leggy growth and to encourage stocky, sturdy plants with a well developed root mass rather than lots of top growth. They really love cooler roots when planted deeply into the garden. That seems to be the consensus among professional pepper growers at any rate.

As to top watering 'drawing" air into the soil, that is difficult to imagine given the way osmosis works. The water fills the air cavities in the soil while displacing the air in those spaces at the same time.

So I guess we will just have to agree to disagree on methodology then.

Dave

    Bookmark   March 20, 2012 at 9:54PM
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