Seed Starting With CFL's

ehsteveMarch 18, 2012


I'm trying to start tomato and pepper seeds indoors to get a jump on the growing season. When the weather is warmer I plan to transplant them outside. I only need the light to give the seedlings a kick start, not to produce fruit. I have the seeds in a 12" x 12" starter kit. As it's the first time I've tried to grow anything like this I've got a few questions:

1. Bulbs I currently have are a 60W (equivalent) 2700k, which I currently have a light fitting for. I also have a 100W (equivalent) 5000k, which is too large for any of my current desk lamp fixtures (doh!). Will these two bulbs be sufficient or will I need additional bulbs?

2. I plan to run the 60W one at first until I can sort out a lamp that can hold the larger 100W bulb. Will the 2700k initial light be too red for a seedling? I.e. should I get a bigger lamp fixture ASAP?

3. Rather than get a bigger lamp fixture would a 60W 5000k bulb work, given how small the space is and the lamp will be right above the seedlings?

4. Once I get a fixture for the 100W bulb should I run them both at the same time or would that be overkill for such a small growing space?

5. Can I leave the lights on 24/7 to grow the seedlings faster or will that weaken the plants for when I transfer them outdoors?

6. Can anyone recommend a decent lamp fixture that will hold a 100W CFL? Preferably a desk lamp style one so I can more easily suspend it directly over the plants.

Thank you for any help with these probably dumb questions.

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For a 12x12 I would recommend a 24" florescent fixture and two 24" 6500K T5HO bulbs. Would allow you to expand to standard flat size, which allows you 24 3" pots. Guaranteed, you will not be satisfied with 12x12, and when you need to up pot your seedlings you'll need the extra.

A perfect microgarden would be the above fixtures, a standard flat with cover, and a heat mat with controller to fit.

    Bookmark   March 19, 2012 at 12:31PM
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mistascott(7A VA)

Probably not enough light from those bulbs to get them very far along as seedlings (without supplemental sunlight), though you might get by for a little while with such a small area. I don't think you are anywhere near overkill with those two bulbs; I would recommend more light.

There is no such thing as "too red" with fluorescent bulbs. They all produce a sufficient range of wavelengths for photosynthesis.

You can leave them on 24/7 and probably need to with that little light output. Nightshade family plants are not hindered by constant lighting, but others are.

Do your bulbs not physically fit in the fixture or are you going by the 60 watt incandescent bulb safety rating for most desk lamps? If it is the latter, you do not have to use those guidelines for CFLs because they produce only a fraction of the heat of incandescents. You can easily put a 100W equivalent CFL in a 60 watt rated desk lamp.

As for fixtures, you probably should look into getting either several 6500K (or so) CFLs that produce 1200-1400 lumens each and a couple clamp lamps from Home Depot (~$8 each) or else a 2'fluorescent fixture as the previous poster suggested. Desk lamp setups tend to get a bit difficult to manage as the plants grow, but it can be done. How far you go should be determined by your interest in producing something nice and your budget.

    Bookmark   March 21, 2012 at 12:28AM
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Thank you both for the replies.

With the size of the operation - I have a small rooftop terrace area to grow in (once the seedlings can go outdoors) and am only looking for a total of 5 plants out of the starters (2 each of two types of pepper and 1 tomato) as not much more than that will fit.

With the 100W bulb - the lamp I had handy has a reflector inside that is set too far away from the socket and has too small a hole for the larger base of the 100W CFL. It fits an incandescent bulb and lower power CFLs but the 100W one won't screw in.

I'll get a couple of clamp lamps from Home Depot this weekend and then see how it goes with the two 100W (equivalent) 5000K bulbs I currently have.

    Bookmark   March 21, 2012 at 9:09AM
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I assume they are 26 watt CFL's. That should do for what you want them for. I usually prefer the tubes to give a larger light source, but if that's what you have it should get you by. Make sure you rotate your plants as they will tend to lean towards the smaller light source.

    Bookmark   March 21, 2012 at 11:59AM
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