Like many plant types, lettuce greatly benefits from starting the seeds indoors and transplanting into the garden. Direct sown seed will generally grow, but are fragile and you will be at the mercy of nature - weather, birds, insects, rodents, soil borne diseases, etc. Additionally, it is very difficult to direct sown a perfect planting distance and when it comes to lettuce, this is critical.
The preferred method, the one that professional growers use, is to start your seeds in flats, cell trays, or even in pots in a cold frame, in early spring. Space the seeds to one inch apart, cover lightly with fine seed starting mix, and keep moist until the seedlings emerge. [Continued Below]
Each packet contains one gram of seeds.
[Continued from Above] Lettuce germinates in seven to fourteen days at 60-70F. When the plants are a few inches tall and you have prepared the soil in your garden, transplant spacing them four to six inches apart. Keep them watered until the plants are established. At about six inches tall, thin them to a final spacing of ten to twelve inches. Control weeds by mulching or periodic cultivation and fertilize as needed during the growing cycle with Nitrogen rich natural fertilizer like kelp meal and/or fish emulsion.
This step of thinning is especially critical for heading varieties of lettuce. If you don't space them properly, you will still have lettuce to eat, but the pressure from crowding the plants will create a competition for water and nutrients and they will likely not head. One of the most common "least favorite" gardening tasks folks have (myself included) is thinning. It feels like you are wasting seeds, time and killing poor little plants. But think of it as a required part of growing healthy lettuce. Plus as a reward for doing the thinning step, the plants you remove will give you an early season salad. I guess you can think of it as an early season harvest.
The other error that people make in planting their lettuce, especially heading varieties is their timing. It is critical that you time your sowings and your harvests. Sow early, transplant early and plan to harvest your crop before the summer heat comes. Heat is an enemy of lettuce as it is another stress that will cause the plants to bolt. Heading varieties are not forgiving like many other garden vegetables. As a matter of fact, at temperatures in the 70-80F range, head lettuce varieties will skip the heading stage and bolt (flower and go to seed). Again, plan your lettuce planting. The optimal temperature range for growth is 60-65F.
For continued salad makings during the summer months, do succession plants of slower bolting leaf lettuce varieties, as well as other leafy greens, and in mid to late summer, you can replicate your early spring process and grow another crop of head lettuce as the temperatures start to cool down in the fall.
In addition to the lettuce varieties on this page, here are other greens that you might be interested in adding to your tossed salad: