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Lightbox suspended

Four-fluorescent lightbox

Another seedling room set-up task checked off today: hanging the lightbox. Not exactly a big job—the chains were already there from last year—but having it in place is a big visual reminder in the Milkhouse that we’re heading into spring. The box, given to me two-three years back, has four 48″ fluorescent tubes on 5″ (12.5cm) spacing. Raised up a bit more, it gives pretty good light to the whole tray, which is about 3.5’x4′ (1×1.2m). It’s been a welcome bit of much-needed space for larger seedlings, though this year, with the barely-heated greenhouse plan, maybe it won’t be so critical. I still have to line the tray with plastic, and possibly get round to giving the box a coat of white paint…



  1. I recommend you cover the entire construction in aluminium paper. It will increase the light yield, and also trap the heat from the lighting.

  2. Johnn

    As far as i know. fluorescent light bulbs don’t generate much heat. But the aluminium paper construction is a good idea for the light yield, if required by the way.

    I decided not to use the aluminium paper and i am doing just fine without it. you have five bulbs which is more than enough for the one tray you have there. You can problably fit about 2 more trays along the length of the light/table.

    I would not raised the light fixture too much. It might encorage fast growth with very thin stems / weak plants. The height right now seems fine. Good luck with your plants!.

    By the way, a first timer here in your blog, very interesting. I really look foward reading more, and i thank you for it.

  3. Johnn: Glad you’re enjoying the blog. I’ll have lots more crammed under that light fixture in no time, you’ll see! :)

  4. LF

    Thanks very much for sharing. It’s really appreciated by beginners like myself.
    I have a couple of questions …This will be my first attempt starting flowers/veggies from seed using lights. I have a double 4 ft. florescent fixture that I plan on using…..the room is a “warm” room in our basement…
    My question: how high above the seeds should the fixture be placed?? I plan on using a two 4ft “cool” white blubs. I have read bulb placement should be anywhere from 1 or 2 inches above the seeds, to over 12 inches. I’m a bit confused.
    Also, should the clear plastic cover be used to provide a “greenhouse” when using lights? I don’t see any covers over your seeds/seedlings.
    Thanks very much,

  5. LF: You’ve just about got it all sorted! Here’s what I know…

    Most (North American) common garden veggies are covered when seeding, and can germinate in little or no light. They need moisture and heat. Soil temperature of around 70°F is optimum for most, so if your room is 65-70, you should be fine.

    Putting clear plastic over the tray or pot (if you look back at some other seed-starting pics, you’ll see the plastic I use) keeps the moisture in, so you usually don’t have to rewet until germination (or for at least a week), but always check! Some people put a few holes in the plastic to allow air circulation, but I don’t, I lift it up to peek every day, and don’t seal the edges. The plastic also creates a greenhouse effect, trapping heat from the lights and heating up the soil a bit more. Plastic does about the same thing as those clear tray covers.

    Oh, you also want to remove plastic as soon as germination starts, because it’s not good to keep seedlings and the soil surface too wet and humid, that can promote…disease.

    As long as you’re clear on the effect of plastic—retain moisture, increase soil temperature—common sense and keeping an eye on things should guide you well.

    Regular 40W fluorescents are quite weak. The whole comparison with the sun thing is quite complicated, I’m still chipping away at it (you can find lots of good articles online, for one, it has to do not only with intensity, but usable spectrum), but basically, you need to keep fluorescents quite close or the plants will stretch towards it. 2-4″ is usually recommended and works out well for me.

    However, once the seedlings start growing, unless they’re in small pots or flats that fit directly under the lights, the plants right under the lights will grow faster than the ones on the edges, and as you raise the lights from them, the ones on the edges start getting further away. It sounds more complicated than it is. But keep in mind that even an inch added distance from the light makes a measurable difference. So, you just figure out height adjustments as you go, and probably rotate trays every day or two if you can to try and give all seedlings the same amount of light. Or you can install more lights.

    Overall, my advice is to try to keep things under lights for the least possible time. Instead of starting a tomato at 8 weeks, start it at 6. For many veggies, the extra growth indoors may produce a bigger, nicer-looking seedling (if you manage to not stretch ’em), BUT, this doesn’t necessarily translate into faster growth in the garden. The longer a plant is in less than ideal conditions, chances are the more adjusting it has to do when it gets set free!

    It’s really pretty simple, especially once you’re been through it once. If something doesn’t seem to be working out, don’t hesitate to plant some more. It’s almost never too late to start things…late, even if it’s way after the recommended starting dates.

    Hope that helps! Just my opinion based on my humble bit of experience, but it shouldn’t be far wrong… :)

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