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T8 Fluorescent Problems

Posted by quimoi z5 PA (My Page) on
Wed, Aug 18, 10 at 1:41

I recently splurged on a 3-shelf Flora Cart and, since our electricity is expensive, I ordered T8 fixtures. I didn't realize how different and limited the choices in bulbs were in the T8s.

My plants aren't doing well and I hope someone can help me.

Indoor Gardening Supplies sent the fixtures with Sylvania Octron XP, 32W 5000K, F032/850/X)ECO3 bulbs. Their description of T8s is:

T8 Lamps
3000 Kelvin Blooming
5000 Kelvin Growth/Blooming
6500 Kelvin Growth

Since I was afraid of burning my plants, my initial time was fairly short (4 hours, I believe). I have a lot of small plantlets and put a few on a nearby windowsill.

Although I have gradually lengthened the time, my plants aren't doing well. Several started growing straight up, but others seemed to show signs of too much light. Superman, a plant which had been doing well under a fairly dim section of the old light, looked especially bad. Yet when it was put at the end near the window, it seemed to reach toward the natural light (the window light is minimal).

I tried changing one bulb on each shelf to Verilux Natural Spectrum, F32T8VLX, V06032, 6000K, but didn't notice any difference except in the color of the light.

The plantlets on the windowsill are far ahead of the ones under the light now. They have buds, unlike the others. At best, a few of the plants don't look bad, but others definitely have funky centers or are growing up, etc.

Some of my plants had just begun to look good and I gave in and replaced one shelf with a T-12 model. However, I would like to make the T8s work.

The only other thing I can see to try is something like this bulb:

Ushio F32T8/830 32 watt 3000 Kelvin T8 Fluorescent lamp

F32T8/830 Lamp Specifications
32 watts
Color Temperature: 3000 Kelvin for flowering and fruiting
Color Rendering: 86 CRI
MOL: 48 inches
Initial Lumens: 3050

Any help would be much appreciated. We only have one other T8 fixture in the house so it's not so easy to use a lot of extra bulbs. I hate to buy new shelves, but will do it as a last resort.

Thanks for any ideas. I've gone cross-eyed trying to understand this light thing.

Diana in PA

Follow-Up Postings:

RE: T8 Fluorescent Problems

Diana -

I use T8s. I am too cheap for Floracart - so mine is Costco storage rack $80 a piece plus fixtures. I am replacing my T12 fixture gradually when the old ones give the ghost. So far I was successful except when my timer died and the plants got 24/7 light and got badly burned my best guess in a week.

I would say 10 inches above the plant leaves should be right - what's yours?, 10 hours average. I usually buy Phillips lights with hi K, but theoretically it should be better - 1 hi K, one low K - to utilize bot sides of spectrum.

There are always special requirements plants - Superman wants T12 - keep it on T12. T8s will be of more advantage for "other gesneriads" and hi light requirement violets (are they dark green leaved?). Kohlerias will thrive on hi light.

RE: T8 Fluorescent Problems

  • Posted by minimac 6 So In. Louisville (My Page) on
    Wed, Aug 18, 10 at 22:51

Hi Diana,
I'm trying the T-8s, also. Right now I'm only using them on my isolation shelves. When I sat them up I left them on 24 hrs straight for a couple of days. Somewhere I read (don't know where) it was a good idea to do this because in the beginning they burn so bright, after that, then I placed plants on shelves. Lights still seemed bright so I lowered shelves probably 12 to 14ins. from top of leaves to bulb (miniatures and standards) and left lights on for six hrs. and gradually increased light half an hour longer each week till they were on eight or nine and a half hours. Room also gets filtered sunshine.They grew and bloomed with no ill effects. All I can tell you about the bulbs - they are Phillips 32w natural sunshine. No longer have the box.
Plants reaching up perhaps they are trying to protect the crowns. I can only suggest cut your hours way back for awhile and lower the shelves or raise your lights. Then gradually increase.
When you bought your light stand from IGS did you just buy the stand alone with trays, and then separately bought their T-8 fixtures or can you now buy the stands (kits) with t-8s. The last I looked they only offered the stand kit with t-12s. I was looking the other week at their seedling carts. When you buy the kit = cart with 3 shelves, 12 trays, plus light fixtures - it looked like they still only offered the T-12s. I would like the t-8s, but they usually say "sorry no substitutions". The kit is less expensive than buying separately.

Hope you can get things straightened out. You have to love those carts. At least now its easy to raise and lower as needed. You'll figure it out.
Good luck,

RE: T8 Fluorescent Problems

I appreciate the responses!


Thank you so much. I believe you are suggesting changing to one in the 3000K range? From what I can grasp, that one has the most red in its spectrum (or something...remember the eye-crossing). They are roughly 12" away but nothing really looks good. I only grow AVs, no other gessies. One that upset me was Arctic Frost. I don't usually grow it under lights but I had it in the center and that spot seemed a little bright for many plants; surprisingly, I had the nicest one ever, nice foliage for the first time, and then it started to bend up.

There is nothing wrong with the large shelves many people use. It just took me a long time to get one and then it was boxed in the garage for a year or so and then on the porch for a couple of years. After I gave up and bought the Flora Cart, it has put together in the basement. It's kind of strange here at times. I am disabled with a disorder that affects my shoulder, arms and hands so I'm somewhat limited.


I think that was probably a good idea on the lights. I probably read about the "burn in" after the fact. I started with a very short time and the lights are as far apart as they would go!

I was going nuts (I must enjoy it) trying to choose a stand and finally just called IGS and asked how much it would cost to substitute the T8s. I may have emailed first, but I also called because I didn't know about shipping and that quote had included shipping. I thought it was relatively reasonable.

Replacing the one light with a T12 cost quite a bit though, but I can use the T8 shelf to convert an old plant light for spring seed growing. I put Gro-Lux tubes in the new shelf and my reds are certainly redder :).

The cart is nice, although I am a bit short for it. It is easier to move than the utility stands too so that's a plus.

I have since bought a 24" T12 stand from another company. I know that size isn't practical but I always seem to be running them anyway for minis and such.

Diana in PA

RE: T8 Fluorescent Problems

Diana -

sorry for being quiet for a long time - my home comp crashed.

If your Arctic Frost is bending up - it is not enough light. I would say 10 hours shoud be right for 12" and 6000K tubes. My best guess that a mix of 6000 and 3000k tubes would be better because it will cover both wavelenghts plant's chlorophyll could utilize.

But - you know your plamts and their needs better than anybody else - keep experimenting and you will find what works for you.



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