Is this a problem?

creister(z7 TX)February 19, 2005

I recently purchased a 72 unit growing tray. It has 6 rows with 12 units per row. I also installed a 4ft. shop light purchased at Lowes. I started growing my tomato seeds. I just centered the light in the middle of the tray. Now that the seedlings are up and growing, the ones on the outer rows are bent towards the light. I started moving the tray every 2 hours so it would be directly over 3 rows, then switch it back to the other side after another 2 hours. My concern is that I will be growing leggy plants. I should have bought two lights, but another one wouldn't get put up for quite a while, so will have to live with what I got. Should I continue to rotate the tray position (during the week will have to rotate about every 7.5 hours), or just center the middle of the tray directly under the light? or am I worrying over nothing? I have never grown under lights before.

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jkirk3279(Z5 SW MI)

You're not worrying over nothing. Wait, is that a double negative?

You will get leggy plants, and even with two lights you still might.

Florescent lights, unless overdriven, aren't quite bright enough for most seedlings.

You can help the plants most by getting a small $ 9 fan. The breeze will tell the plants to sturdy up, just like a human building a muscle by lifting weights.

    Bookmark   February 20, 2005 at 2:38AM
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shrubs_n_bulbs(z8/9 UK)

Keep rotating. Once a day is enough. If the seedlings are leaning then they are growing a bit leggy. Try to keep temperatures cool. The fan will help. Reflectors would help because shop light light goes out in every direction. Collecting all the light onto the seedlings would make a big difference. I guess that would take as long as fitting another light? Can you fit a more powerful bulb? That would help. As you already know, a second light is the solution.

Isn't the 4' light longer than the tray? Can you rearrange the units into a 24x3 line instead of a 12x6 one? Does it have two bulbs or one? I'm guessing the tray is about a foot wide, so two bulbs an inch or two from the seedlings would be perfect.

    Bookmark   February 20, 2005 at 5:10AM
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jkirk3279(Z5 SW MI)

"Collecting all the light onto the seedlings would make a big difference."

I forgot to mention that, thanks. I have some recycled plastic mirrors about the place, and tried propping one up by the light bank recently.

Still wondering about the right angle for the plants. But of course, you don't need special mirrors, just cardboard with aluminum foil taped to it will do just fine to bounce the light around.

    Bookmark   February 20, 2005 at 4:27PM
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creister(z7 TX)

Thanks for your suggestions. The fan is up and running. I also went to Lowes and bought another light. It isn't hanging yet, but is set up at about a 95 degree angle to the hanging one behing the tray. I hope it all helps the precious tomatos. I might get the light hung tomorrow hopefully.

    Bookmark   February 20, 2005 at 10:07PM
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cbars(z5b6a MO-Kansas City)


Move the light down to within two inches of the leaves.
Keep the fan going and temperature around 60 F.
Seedlings should sturdy up but you will probably still have to rotate the tray or move the outside seedlings to the inside of the tray.

What are you going to do after you transplant? Have you given any thought to that. In case you didn't realize it, once the seedlings get their first set of true leaves, they need to be transplanted into a 3-4" pot and then put back under the lights and continue to bottom water. This will slow vertical (plant) growth but encourage root development. Once they reach 8", they can be hardened off and then planted outside.

Lots of folks think that they put a seed in that peat pellet, grow a plant, and then plant it outside. Won't work.

Good luck.

Forgot to mention - lights should be on a minimum of 16 hours per day.


    Bookmark   February 21, 2005 at 3:35PM
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creister(z7 TX)

I installed another shop light with one regular and one bathroom bulb next to the other one. It appears that there is now light directly over all the seedlings. I also have the fan on low. I was wondering how hard the air needs to be moving. Right now, all the seedlings just kind of gently vibrate, you can see them moving. I didn't want to over do it. I also placed aluminum foil under the tray and along the back wall behind the trays. The dull side is facing out. I also leave all the other garage lights on. Should I leave the fan on during the dark hours? After all of this, the outer rows still have some plants plants leaning in, which puzzles me, as there is light directly above them. About 2 inches above. Thanks for all the help, as I am new to this.

    Bookmark   February 22, 2005 at 9:44AM
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shrubs_n_bulbs(z8/9 UK)

Any air movement at all is sufficient. Use a very gentle fan on small seedlings to avoid dehydrating them.

The outer plants are under the lights but it is still brighter on one side so they lean a bit. Reflectors all round the trays would help, or you could experiment with moving the two lights apart slightly to provide a more uniform light to the outer seedlings.

If you don't rotate the seedlings at all it would be interesting to see if there is any difference between the ones getting warm white and the ones getting cool white light.

    Bookmark   February 22, 2005 at 11:54AM
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creister(z7 TX)

Shrubs, you must have read my thoughts, as I was wondering if the seedlings might prefer the warm bulb over the cool, or vise versa. I did alternate the bulbs, going cool,warm, cool, and then warm. It seems the seedlings on both sides still lean it. I may experiment pushing the lights futher apart.

    Bookmark   February 22, 2005 at 3:11PM
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jkirk3279(Z5 SW MI)

" It seems the seedlings on both sides still lean".

Try putting up some light-reflectors behind the plants. Cardboard with shiny aluminum foil taped to it should be fine.

    Bookmark   February 23, 2005 at 12:14AM
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Rollie4620(Ontario, Canada)

I have a cheapy little octagonal shaped "greenhouse", (metal tubes with a plastic cover) on a table in a West facing window. There is a 2 foot fluorescent light (on a timer for 16 hrs/day) inside, and a small computer fan. I planted tomato seeds 2 weeks ago and put them as close to the light as possible. The seedlings are about 1 1/2 inches high now and the 4th and 5th "true" leaves are just beginning to show. The seedlings bend to the light early and late in the day and towards the sunlight during the day. I don't rotate them as they bend back and forth from the light to the window over the coarse of a day with no problem.

I'm watching them closely to see if they start to get "spindly" and I may have to switch to more fluorescent lights on "overdrive". I think that the fan has made a big contribution to making the stems thicker and sturdier.

    Bookmark   February 23, 2005 at 7:01AM
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