The plywood boxes I built are a little complicated to describe in words. I framed those boxes with 2x2s and screwed in 1/4" plywood as a skin. The frame actually keeps the structure square over the years. You can see my oldest plywood box at: http://www.brandylion.com/images/front_box.jpg Using rough pine 1xwhatever is much easier because you don't have to build a frame. Right now, I make all my containers 18.5" deep which provides more flexibility in future years. 1x10 pine boards are actually 9.25" wide so I strap two of them together. To strap them I cut up a bunch of 2x2s into 18" lengths. Make the long sides first by putting the 1x10s side by side and strapping them at each end with the 18" 2x2. I screw through the pine into the corner straps using 2 1 5/8" screws. You'll have to drill pilot holes first and only use two screws per board and alternate them because the short side will also screw into that same corner strap and you don't want the screws hitting each other. Two screws is plenty since there isn't much force from the soil against the walls. Once you got the two long sides with their corner straps secured at each end connecting the 1x10s (or different depending on how deep you want your planter), you need to put an 18" 2x2 strap every two feet. So if your planter is 4' long you put one strap in the middle, if it's 8' long you'll be putting 3 straps spaced every two feet. When your long sides are finished cut pieces of 1x10s to how wide you want your box. Set the long sides up on the ground and screw the pieces into the corner straps and you'll have a square box with no bottom. It helps to have a framing square for this step to make sure all the corners are 90 degrees. For the bottom I use whatever scrap wood I have laying around -- even 3/4" plywood. You can use the same rough pine used for the sides too. Turn the bottomless box upside down and screw the boards into the sides. You don't need that many screws, perhaps 1 every 2 feet. If you use 1x10s or whatever you'll have to strap them together and the straps can be inside or out depending on how you plan to use the box. My boxes either go into a frame or sit on cut 4x4s or 6x6s. If you use 4x4s, space those appropriately. If you have a 4' box you can get away with 2, a 6-8' box will need at least three, 10' will need 4, etc. The screws holding the bottom into the sides cannot hold the weight of the dirt, the planter must be supported by some frame or structure from below and that depends on where you're going to put the box. After you have the box screwed together, paint it inside and out and then drill holes in the bottom. I use 1/2" holes and I drill a lot of them. Then screw the box into the platform and fill with dirt. This March/April I'll be building 5 more of these of all different sizes so maybe I'll put together a picture log if there's interest. Here's a pic of 3 of my boxes early Spring last year. The white one on the right sits on 4x4s and the two on the left have their own frame that supports the bottom and the weight of the soil. http://www.brandylion.com/images/rear-boxes2.jpg The boxes on the edge of the roof line were the first ones I made out of that treated wood which I don't use anymore. Here's a view later in the summer. http://www.brandylion.com/images/summer-rear.jpg

Lettuce can also be mass produced easily and cultivated in even smaller pots like a small plastic drinking cups or yet smaller net pots in any self-watering planters or diy simple hydroponic or soilless growers. With hybrid soilless and hydroponics horticulture methods, the growing medium can be made of anything, including potting mix, pea gravels, perlite, or strips of jeans, and is secondary as long as the material can minimally support plant roots structurally. There are some variations in how each soiless method or grower deliver moisture, nutrients, and air to the roots, but they all work off utilizing similar horticulture principles and objectives of growing healthier plants more simply and efficiently with less by feeding the roots directly with nutrients and air.

I typically grow stuff like greens/snow peas etc in containers with 6" of depth. Actual mix depth is 4-5" You will need to water more frequently than if the container were deeper as a higher percentage of the water is lost to evaporation, but depending on your perspective that may be a good thing or a bad thing. Anyway, 6" of depth is adequate for *almost* everything in terms of root depth. With the exception of plants grown for their below soil parts overall volume is more important than depth. Even volume isn't all that important unless the roots systems will tangle each other massively and this won't happen with lettuce. Greater volume just means more water holding capacity. If you are skeptical that 6" of depth is adequate for nearly everything consider that commercial self watering pots like Earthboxes hold about 6" of mix and clearly lots of veggies have been successfully grown in them.

Varietal differences plus the growing methods can't really be compared. Soil in a window box will dry out 100x faster than the commercial varieties grown in the ground. Lettuce is a water hog since it is 90% water to begin with. But that soil moisture level must be consistent and that is impossible to do in a windowbox. Water it well with cold water 1 hour before harvesting it for the most crispness the particular variety will allow. Also don't let the leaves get too big/old before harvesting. Dave