So... working up a website for this turns out to be more work than I have time to give at the moment.
Instead, here's some albums of pictures I threw together on photobucket.
Two shots of the LED tape, plus one of the bloomhouse. I used velcro plant ties to attach the tape to the shelf above. Not optimal, but it was fast and I didn't need to break out the soldering iron.
More after the break.
First two weeks. Germination was extremely fast, within three days. Progress after that was slow. That appears to be because the light intensity was not high enough; sprouts need a lot of light. If I had an adjustable light fixture I would have set it maybe 2cm above the plugs. Temperature swings were pretty high since I placed the bloomhouse up against a south window.
The first row of plugs was seeded with spinach, which failed to sprout. I think the seeds weren't deep enough into the rockwool. The rockwool plugs themselves are seated in a bed of puffed clay, all set in a stamped aluminum-foil baking pan. The pan was a quick, cheap solution. I'm seeing some evidence of corrosion on the outside of the pan so this may not be a good idea over the long term.
Next two weeks.
As you can see, leaves were long and stems were leggy. I think this is a combination of temps peaking over 85 °F and insufficient light in the first few days; the plants were already bolting.
You can also see algae starting to grow on top of the plugs. This is inevitable when sunlight and water meet.
To put things in perspective, commercial growers are harvesting by the end of this period.
Weeks 5 and 6.
Finally putting on some mass. Since the stems are so leggy they all fell over and coiled. Growth accelerated remarkably during this period.
The small white specks on the clay media are nutrient salts. I keep track of the nutrient concentration with an EC meter, checking every two or three days and aiming for around 800-900 ppm. My nutrient solution is around 1200 ppm so I alternate between nutrient solution and filtered water for fill-ups. The media I used buffers a significant amount of water and nutrients; for DWC or NFT methods try to mix the correct concentration for your crop since no wash-out water is necessary.
In the later images you can see the beginnings of a white mold infestation. Probably pythium, but it could be anything. I washed my hands but didn't mask and sterilize when handling parts of the system so there are certain to be skin flakes and a cornucopia of bacteria and other critters introduced.
The inner three plants are fine, but the one to the right is having trouble fighting off the invaders and the one to the left is still a runt.
Leaves reached past the LED tape. You can see that some of the leaves are touching the tape; there was no sign of heat stress or damage on these leaves. This suggests I can place lighting very close to the plants throughout their growth cycle.
The last shot shows the full tray wilted. I didn't add enough water on the previous cycle (aiming for about an inch in the bottom of the pan) and the bloomhouse was left unzipped to reduce overheating. It dried out while I was at work. On the plus side it seems to have stalled the fungus growth. I topped off this evening and we will see if the plants survive.
I haven't done a taste test. The lower leaves are thin and have been in contact with the salt-crusted and fungus infested growth medium. The upper leaves (within about two inches of the LED lights) are more closely spaced, properly ruffled and more intensely colored. I was planning to try a few of those this week, but we will have to see if they come back to life first.
While a very good grow program can produce lettuce in four weeks, stressed plants will struggle to produce a few edible leaves in twice that time. If your seedlings are leggy or your plants start to bolt, don't bother hoping they will snap out of it. Make a baby lettuce salad and start new seedlings. If you see fluffy fungus in small surface patches you are probably ok; try a peroxide treatment. If you see dense clumps of the stuff or if it starts attacking roots and leaves then cut your losses, harvest the tray and sterilize everything before the next batch. Remember, plants attacked by mold are generally safe to eat (at least, the parts that are not affected). Plants attacked by bacteria are dangerous; if the plant seems to be sick throughout (not just small bad spots) and smells bad or is frothy, foamy or slimy then throw the whole thing away.
LED lights need to get very close to seedlings. So do other lights, but LEDs are cooler and can be placed closer, requiring lower overall intensity if properly placed. You really do need some kind of movable fixture, which can be expensive or difficult to build. An alternative might be to use trays with spacers of some kind underneath to raise them up to the lights.
Deviating from the 'internet consensus' on growth media is a bad idea. Pick one established technique and stick with it. I could have used my cheap tray and filled it with cheap coco coir as well, with a little more care given to watering twice a day. Drainage would have been a problem. I should have used deep-water culture: a plastic tub about 4" deep with an opaque lid, net pots with rockwool inserts and an airstone and pump to aerate the nutrient solution. I would have liked to use NFT, but the pumps and channels were out of reach for my meager budget.
At minimum I should have used plastic wrap to seal in the clay puff media. Aluminum foil might have kept the algae at bay too.
Temperature control is very important for lettuce. Avoid direct sunlight unless you have automatic environmental controls. My next batch will grow away from the window and should be stable in the low 70's.
Cleanliness is important. Just washing your hands and your equipment is not enough. The bloomhouse I have has two zippers for the door; I should have done all my plant handling with the door-flap down to minimize exposure to contaminants. For other setups, don't open the reservoir / channels / root bundles more often than necessary. If you are serious about growing food, especially plants that take more than a month to be edible, consider buying a painter's suit or cleanroom gown and face mask. Also consider getting some food-grade peroxide to be diluted and used as an antimicrobial treatment.
Plants can be spaced very closely. These are just under 5" apart, which I thought was going to be very crowded. Turned out to be a bit too wide; I should have put in three rows 3" apart or so in all directions. A good DWC or NFT system will allow you to re-space the plants if necessary. My hybrid system would have caused root damage if I tried to move the plugs after the second week or so.
I'm probably not going to have time for a second run until this summer. I will definitely try the same black-seeded Simpson lettuce since it germinated so very quickly; hopefully I can rig something to position lights properly and avoid the issues I had with this first run.
I need to deal with the rest of my LED tape properly, assembling the full set of 1 roll red, 1/4 roll blue and 1/4 roll white for each of four trays with soldered connections.
I want to try a few kitchen herbs. Fresh herbs are crazy expensive, but seeds are fairly affordable.
I have some cat litter buckets that I've been using to store growth media, nutrient solution concentrates, etc. I want to attempt some bell peppers and tomatoes in these as DWC. That might have to wait until later in the summer since I'll need more LED tape.