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Tested ok but ...

Posted by jduren 5 MO. (My Page) on
Sun, Feb 10, 13 at 12:17

I did a trial of three different seeds in a self watering seedling tray and it tested out okay. The petunias and one variety of morning glories came up. I used the t12 fluorescent lights as a heat source from above and heated the trays just fine.

The morning glories were up and running in 48hrs and this forced me to pull the lights back losing my heat. The petunias came up in 5 days.

Is it trail and error with mixing seeds or putting the same variety in a single tray to eliminate this problem? I just put a 72 cell Lobelia/coleus out and I hope this isn't a problem?

With the petunias and morning glories up I have been moving the tray to the window for natural sunlight. My guess is this is okay?

Because the t12 fixtures/bulbs are being eliminated I purchased t8 fixtures but don't produce the the same heat response as the t12. Guess I can just use the t12 for germination and the t8 for growing....

Follow-Up Postings:

RE: Tested ok but ...

If the cell packs that you are using in the tray separate into smaller sections, then you can always pull out the different seedlings as they emerge. As long as you sow them cell pack by cell pack instead of mixing them.

Last year I had some issues trying to many different types of seed in the same tray and they were not in any kind of separate cells, just planted directly in the tray. I wont do that again. This year I am starting everything in little 3oz plastic cups inside of the domed trays, so that I can just pull them cup by cup as they sprout.

RE: Tested ok but ...

Is it trail and error with mixing seeds or putting the same variety in a single tray to eliminate this problem?

Best is only one thing in each tray or container or whatever as they will all have different germination rates. Even if they aren't made to automatically separate you can cut them apart.

moving the tray to the window for natural sunlight. My guess is this is okay?

It is ok but most likely won't be enough light to keep them from going leggy. Window light alone never is. Supplemental lighting is needed, even in a greenhouse this time of year.

To avoid confusion. the lights are used for light, not heat. The low level of heat they generate is only a secondary benefit at best. So since you have lights, why aren't you using them instead of a window?

No T8's don't produce as much heat but they produce almost 2x as much light as T12s - which is why they are so good. Other sources of heat for germination (none is needed for growing on) like heating mats or even incandescent lights are normally used for heat, not the fluorescent lights.


RE: Tested ok but ...

I put the t12 lights on the seedlings for light but get heat as well. Two birds/one stone. As far as i know I only need the heat for germination, correct?

"Seeds need warm soil to germinate but roots need cool soil to grow. :) Seriously, bottom heat on very young seedlings can easily cook the tiny roots..

it also contributes to extra humidity which can lead to damp-off and death and it stimulates excessive top growth that the roots can't yet cope with.

Most all plants, once germinated, much prefer cooler temps for slow sturdy growth. That's one reason why nurseries and greenhouses shoot for a max of 65 degree air temp. So do your plants a favor and turn off the heat blanket.


RE: Tested ok but ...

I guess not to cause confusion.. The t12 and as I checked today the T8 lights at 2" above the tray are providing enough heat to germinate the seeds. Unless I need a regulated heat source like 85 degrees this should work fine.

RE: Tested ok but ...

We are talking about two different situations jurden - seed germination and then growing the plants,

Very few seeds need light for germination but they all need heated soil.

For growing on AFTER germination they need light but not heat.

So using lights to create germinating heat isn't nearly as effective nor as energy efficient. First because it is fluorescent which create minimal heat. Plus it is radiant heat not direct and most dissipates into the air and so wasted. Plus it is inconsistent and cannot be regulated. So for every kw used the degrees of heat achieved from lights is minimal when compared to the direct consistent heat created by using germination heat mats.

Then once the seeds have germinated it is time to remove them from the soil heat, reduce the air temperature if necessary, and provide them with as much light as possible.


RE: Tested ok but ...

  • Posted by nil13 z21 Mt. Washington L (My Page) on
    Tue, Feb 12, 13 at 22:40

I don't like cell trays. I like 2.25 in. individual plug pots for versatility. I order a bunch to fill standard trays and then as cells need swapped out they can be.

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