(Revised and corrected on 2/9/11)
I’ve heard time and again, even today if you Google “seed starting,” that you need a bright window for starting seeds. You don’t need a bright window; there’s no such thing as a bright enough window when it comes to seedlings. They need 14 hours or more of sunlight, which is what they’d get if growing outside in late April or May – but you won’t find that in any house window. You’ll get weak, spindly, “leggy” seedlings starved for light that won’t ever do well.
What you need instead is artificial light, and what works best is four-foot hanging shop lights with two fluorescent bulbs. The bulbs needn’t be those pricey full-spectrum thingies; just cool-white tubes. I’ve used these for years and they do just fine. Now you’ll need shelves – more than four feet long to accommodate the lights, and at least 14 inches apart vertically to accommodate growing seedlings.
I use a frame of 2-by-4 studs, two at each end of the shelves, set about 4 inches apart (inside measurement) with the broad sides facing in and out. Fasten them together with a vertical foot-tall piece of plywood or other rigid material, top and bottom, to prevent lean (optional). For shelves you have two choices: One is is to use 1-by-8s or 1-by-10s, four feet long, meaning you can cut a standard 8-footer in half to eliminate waste, fastened to each corner post with an L-shaped angle bracket. Or, you can use low-cost 1-by-4s, each end fastened the same way, but now you’ll need a short cross-piece at either end so the shop lights can hang centered on the two seed flats below that each light will accommodate. Fasten the shelves with a little space at either end to be sure the 4-foot shop light will fit in there. Put the first two-piece shelf about 18 inches off the floor because it’s hard to reach lower than that. Once the brackets are in place, the assembly shouldn’t move much.
Now you need cup hooks and lightweight chain (or twine with a slip knot) to hang the lights from and allow you to lift or lower them. The lights should be kept no more than about two inches above your seedlings as they grow.
As for containers, I use standard 11-by-16-inch waterproof trays with inserts for the seedlings. I begin with cells 1.5 inches wide, to 2.25 inches, potting up to larger sizes if needed to prevent plants getting rootbound before they can go outdoors. These can be found at the big-box stores, by mail order, or for a lot less on ebay.
The plants you’ll want to start this way can be just about anything except corn, peas, beans, root vegetables, and others that don’t transplant well. Ideal candidates are long season crops such as peppers, tomatoes, eggplant, okra (assuming you want okra for some reason), along with the brassicas, kohlrabi, leeks and onions — and all manner of annual of perennial herbs and flowers. Tomatoes don’t like to spend more than 8 weeks in a pot, so plan accordingly. Melons and squashes may be started inside, but no more than a month before it’s safe to move them out.
As to the 14-16 hours of light your little babies crave, I’m not always awake that long, so everything goes on an inexpensive timer.
See, that didn’t break your bank, and you won’t have to go out an buy tomato varieties you don’t necessarily like with aphids all over them.