T8 Fluorescent Problems

quimoiAugust 18, 2010

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

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irina_co(z5 CO)

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.

    Bookmark   August 18, 2010 at 5:42PM
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minimac(6 So In. Louisville Ky)

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,

    Bookmark   August 18, 2010 at 10:51PM
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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

    Bookmark   August 19, 2010 at 12:52PM
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irina_co(z5 CO)

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.



    Bookmark   August 23, 2010 at 7:30PM
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I grow my African violets under t8s. I have for about 2 years. When the tubes are new you either have to put 3 layers of wax paper over the fixture and tubes or turn out one of the tubes. You will burn the plants up if you don't. T8 lights shouldn't be on more then 9 hours a day and much less when they are new.

Remember to watch the crowns of the plants. They will tighten up really fast if you don't watch them. It took me a long time to get it right. Many hours of changing shelf height and light times.

They can be use but error on the side of too much distance and short hours of lighting. It's easier to tighten a crown then opening it up!


    Bookmark   September 21, 2014 at 5:24PM
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judyj(Z5 CO)

Diana, I don't know if it helps. I use two 2 foot long fixtures with T-5 tubes-one 6500K and one 2900K in each. Seems to work wonderfully. They're on about 13 hours a day.


    Bookmark   September 21, 2014 at 6:34PM
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I gave the Floracart with the T8s away. I never could make them work.

Now I'm trying to get something set up with T12s. I do have a T8 shoplight that I used in the spring for annuals and it seems a bit much for some leaves.

BTW, as near as I can determine the Floracarts with the large trays are now discontinued. It looks like the big trays may be the problem. I have mixed feelings about giving that one away but it's too late now. I need to find a shelf unit and space to put it.

(I was really surprised to read this. I lost Superman entirely and eventually lost many other plants. I'm sure it wasn't just the T8s but it was a very frustrating experience. I have now seen where some people cover them with some type of paper.)


    Bookmark   September 23, 2014 at 3:21PM
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Will (AKA wec1957 )

did you mention the distance that you keep the violets at? I'm curious because I haven't really figured that out yet...I'm still getting that "suburned" yellow/brown effect on one of my light stands. I keep different heights and light arrangements on different stands as I'm trying to figure out what works...so any advice is greatly appreciated!!!

    Bookmark   October 31, 2014 at 9:30PM
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I measured mine a while back, now i don't remember the exact figures. i think i have them 15-12" away from the shop light with no cover, and about 6-8" from the light with diffusor (ceiling fixture). the lights are on about 12h i think.
then, i gradate where i put which plants, sturdy ones to the middle, extras past the end (72" shelf, with 48" fixture)
still, there are some plants, that will not loosen up, no matter where i place them. i hope the 2nd generation will do better...


    Bookmark   October 31, 2014 at 10:46PM
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Obviously, I'm no T8 expert :) As of now, I am only using them with leaves and I have some of those covered with the Press 'n Seal plastic wrap which is more opaque than regular plastic wrap.

However, I recently had to rig up a shop light and didn't think I had Gro-Lux bulbs (later my husband dragged one from the garage with 2 genuine Gro-Lux bulbs...). Yes, I know there are alternatives but I didn't have those either.

Anyway, I used a light that I'd had in another room with an old full spectrum bulb called Vita-Lite (they have a twist in the tubes). Well some of the plants adored them. However, after awhile, others started showing signs of too much light. I think this was a good experiment. It showed me that plants really differ a lot in their likes/requirements. A couple of them took off like wildfire under those (Buckeye Seduction was one but eventually showed the effects of a little too much light). Ness' Cherry Confection never did flinch. It liked it.

I suspect T8s may be the same. Some plants may do very well with them but others perhaps not so well?

Diana in PA

    Bookmark   November 3, 2014 at 2:54PM
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Okay-I didn't read through all of these so forgive if I repeat or miss the mark. I have a Gro-Cart and use T-8's. I use one warm white and one cool white from HD. Nothing fancy. Works great.


    Bookmark   November 4, 2014 at 1:21AM
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Vikki(7b / 8)

In my fixtures, I use T8, I put in one bulb with the lowest K value and one with the highest I can find. Currently, one is 2400 and the other is 5000. That seems to give them the broadest band of color, one for the leaves and growth and the other for the flowers.

    Bookmark   November 6, 2014 at 8:13AM
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