Too hot under lights -- did I buy the wrong bulbs?

[Barnowl]

Hi folks, past time I introduced myself as I have read and learned from all of you since the end of last summer. I want to thank you for sharing your experiences and knowledge. I have previously only grown tomatoes from starts and this year I am growing from seed for the first time.

I planted 18 varieties on March 7 (5 days ago) and have kept the room temps btw 77-79 degrees as best I could. I planted in peat pellets placing 3 seeds of each variety into a pellet, using 2 pellets per variety. Some of the seeds germinated after 2 days and shot upward with great vigor. I suspect that it was too warm for too long as yesterday some were over 3” high while other seedlings were just emerging. Last night I placed them under lights and turned the room temp down to 69 degrees. I also plucked the seedlings that were over 3” high.

Yet the temp under the lights is currently 82 degrees and the bulbs I am using are warm to the touch (the ambient air in the room is around 69 degrees). I have read that seedlings should be grown under the lights at cooler temps – which seems impossible with my set up given my lights are the source of heat. I suspect the problem is in the lights I am using – one Phillips 40w natural sunshine bulb and one Phillips 40w plant & aquarium bulb in each of my two fixtures… Did I buy the wrong type of lights???

Jamie

[bcday]

The lights you have are fine. Fluorescent bulbs do get a little warm but they are much cooler than any other type.

I wouldn't worry about the temperature of the air under the bulbs. A small fan circulating the air nearby will help dissipate some of the heat and also encourage stronger stems.

It could be that what you read about cooler temps was in response to a question of when to remove young seedlings from the heating mat where they were germinated. Once they have sprouted, they don't need the extra warmth any more.

It would be better to put the seedlings under the lights as soon as the first ones come up, even if the rest haven't sprouted yet. The rest won't be far behind and the first ones up won't become leggy for lack of light.

[dcarch]

Several things to consider:

1. Air temperature may not be the same temperature on surfaces. it would be better to use a non-contact type digital thermometer. You will see that temperature will be very different on leaves, soil, and air.

2. Flurescent tubes are known as lineal light source, therefore you can give a couple more inches of space above the seedlings without loosing intensity.

dcarch

[Barnowl]

Thanks bcday, I am relieved by your response... All this is new to me and I am having a blast experiencing the wonders of tomato growing first hand. Learning lots and plan on never stopping.

Rigging up the fan was going to be the next step, I will set them up tonight and as you point out the temp under the bulbs will go down...

Dcarch – all that you say makes great sense… I will raise the lights up a little. I was wondering if I was crowding them too much…

[dcarch]

Originally Posted by Barnowl

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Dcarch – all that you say makes great sense… I will raise the lights up a little. I was wondering if I was crowding them too much…

I bought a digital thermometer for less than $10.

I use a 400 watt Metal halide light and the light is 36" above the seedlings

dcarch

[robin303]

Use one regular bulb and buy the Grow light bulb [$10 Homer] keep 2” from the tops. Different light spectrums.

[feldon30]

I think he's using bulbs of 2 different spectrums but actually went a bit over the top with the grow/aquarium light and the natural sunshine bulb. I think those are $15 and $10 respectively?

A cool white and daylight are just fine and I think $4 and $8 respectively.

[Barnowl]

Actually, they weren't that expensive. The natural sunshine bulb was just under $7 and the grow/aquarium light other just under $9 each... the regular ones sell for around $4-5 at the local Home Depot....

Gosh... could it be that something is actually cheaper in Canada?

[dice]

If they end up lanky, it can be a little annoying
when they are still indoors under the lights. They
look spindly and may want to lean over.

Once transplanted into the garden, though, one
just plants them a little deeper (or sideways in
trenches if they are quite long), leaving only
a couple of sets of leaves and the growing tip
above the soil. Roots will grow out from the
buried stem, and you will have a larger root
system sooner.

[Barnowl]

Thanks dice, I was planning on setting them deep in the 8oz cups that I pot them up to when the first set of true leaves form... I've got a question about potting up that I will post separately... thanks everyone.

Jamie