I have been experimenting with various container sizes for growing lettuce. I have been growing tomatoes for decades but lettuce is new to me. I don't worry about the potting soil cost as it quickly pays for itself considering the cost of lettuce. So far the salads exceed my expectations. I have been harvesting lettuce in this 95+ hot windy weather and it is not bitter. I grow in 1/2, 1, 2, 3, 5, and 15 gal nursery pots. Some lettuce does ok in the small pots. I don't see a significant difference in growth habit between 2, 3, 5 and 15 gal nursery pots. Two or three might be optimum. I lean towards the larger sizes because they are easier to water. When the lettuce gets larger it is difficult getting the water into the one gal containers. I consider two gal the minimum to grow out lettuce. I start in two inch rose pots or sometimes three inch pots. Then pot up into the larger containers. Two and three gal are nice for portability and you can grow good size lettuce in them. Five is similar to three but deeper. I place 4.5 pounds of DE in the bottom of the five before the potting soil. I can then place the five in a saucer and fill it with water. The fifteen is prime because the diameter is close to the diameter of the lettuce which makes it easy to water. They are a bit deep so I start with DE before the potting soil. Also the fifteens work well with the plastic mesh poultry netting cage I place around the lettuce for protection from birds, with added wind protection and shading. The lettuce is grown in full sun with a fair amount of wind. I don't pick outer leaves. I harvest the whole thing. The lettuce is kept well watered (wet) It is still early in the game for me so I don't know which varieties work best throughout the summer. Everything I have tried so far works. Some better than others. Southern Exposure has a good selection of summer lettuce. I just received an order of six different summer lettuce types and have begun the experiment. We eat salad every day and haven't had to buy any lettuce for a couple of months. I don't know why it took me so long. Zeuspaul This post was edited by zeuspaul on Wed, May 14, 14 at 20:32

If you have a soil thermometer, you can check the temp of the soil in the "pot". But when I lived in Las Vegas, NV, I did an experiment. I had a lot of stuff growing in 2-gal black plastic pots. They were getting heat stressed. I put my compost thermometer in the soil, and the temp was up to 130F. So I wrapped some plain old kitchen aluminum foil around the same black pots, and took their temp at the same time the next day, and the soil temp had dropped to 90F. Since your container is fairly shiny, you may not have a problem with heat. But if you are using straight potting soil, you'll want to check to see if it dries out too fast. If it dries out fast early on, you might want to add some of those water-retaining crystals to the soil. Sue

How far from the surface the potting mix is isn't critical. In a conventional, top watered container it is common to leave an inch or two of container above the mix, but certainly is not required. Doing this makes it easier to water without overflowing the container. With a self watering container the mix can be below the top of the container or mounded up above it, the plant isn't going to care much. Do you have around 4" of potting mix depth for your lettuce? If so I think you will be just fine. Even this amount is somewhat arbitrarily chosen by me. Removing plants from a nursery container is fairly straightforward. Just turn the pot over and dump them out into your hand. If they don't come right out give the container a squeeze or slide a butter knife along the inside edges to loosen. While there are some plants whose roots need to be treated gently, lettuce doesn't. Most plants respond just fine to having their roots treated fairly roughly. If you get the plant out of the container and find it is a thick mass of roots I recommend (literally) ripping a good chunk of the roots off (particularly if they are circling the bottom of the pot) and then planting them. You will be doing the plant a favor by getting rid of those roots. Lastly, if you feel you have 'mangled' the plant just plant it and try to keep it out of direct sunlight/wind for a day or two in case it wilts. Don't panic if it does, it will likely perk up in a day or three and do just fine.

They are big enough, but so are the sixpacs the nurseries sell with annuals and are thrown away by the millions. I am using a type that open up to allow the rooted plant to be removed without digging it out of a two inch pot. They are called 'rootrainers' as the bottom is open enough to root prune potential tap roots. They come 32 to the tray with a plastic dome. I have found them at Lee Valley and Charlies Greenhouse supply. I watch for them on sale and pay about $12 each. They can be reused many times if not abused. Al