A week ago I started some lettuce, spinach, bunching onion, and broccoli seeds in rockwool and placed them under a Jump Start grow light to germinate. I'm using the Kratky passive method and was able to place the lettuce seedlings in their final homes just this morning. While I'm still waiting for the other seeds to start sprouting, the lettuce shot right up within a few days as expected. Here are some pictures of their progress.
Final Destination (Day 9)
I'm using 16oz Ball canning jars as their final homes. Unfortunately I bought 2" diameter net cups instead of 3", so I had to rig up some hangers out of stainless steel welding wire so the cups sit flush at the top of the jars. The clay pebbles are not necessary in this case since the tinfoil should effectively block any light getting down around the rockwool into the grow solution, but I added them for redundancy since I had them on hand. What I'm not sure about right now is how much light the sproutlings need in a day. I've had it on for about 16 hours, but I figure at some point the plants will be able to have less per day. My conundrum is that I only have one light right now, and once the other vegetables start sprouting, they may still need the 16 hour sunlight for best results, whereas the lettuce plants may not. I suppose I can just move them somewhere dark if it turns out to be too much for them.
I'm not doing any pH testing right now and I may not even be using the right nutrient solution, but I'm going to see if I can make it work. It's an interesting experiment either way. I plan on starting more lettuce seeds this evening with the ultimate goal of having a weekly harvest once (or if) they start maturing.