Leaf lettuce has to be one of the easiest of cool weather crops to grow, but it also is frequently grown poorly. First by cool weather crop, it means that lettuce doesn't grow well in hot weather, but really it means that the long days and short nights of summer cause lettuce to bolt, grow taller quickly, and when it does so in an attempt to reproduce, the laticifers, the latex producing cells that give lettuce it's generic name (Lactuca) mature and the lettuce gets intolerably bitter. So plant lettuce as early as you can in spring, or in very late summer for a 2nd crop. You can even use containers and/or a cold frame for a very early crop.
Here's the problem and my simple rules for growing nice big leaf lettuce plants. Intraspecific competition is always severe because the organisms competing are just about identical; they all need the same thing. With plants it can often be competition for space/light, water, and/or nutrients. Leafy lettuces are easy to plant way too densely because their seed is fairly small and no one wants to put each seed down one at a time, so you just sort of sow it and it's always too dense. But as they grow, a dense stand of lettuce seedlings crowd each other and compete with the result that the plants stay small and become thin and spindly. So here's the steps you must take until you learn how to sow the seed better. Step one: when the seedlings reach 1" in height, thin them out until all the seedlings are at least 2 inches (two fingers) apart. Step two: keep thinning as the seedlings grow until they are at least 4" apart by the time they are 4" tall (width of your hand). Step three: keep thinning until the lettuce plants are at least 8" apart (full hand span) by the time they are 8" tall. Step four: as you harvest, keep taking out every other plant. Step five: eat everything you thin out as you go. And don't spare the water or nutrients, lettuce likes to grow fast. By the time you get to step step three the days will be getting longer (or way colder if in the fall) and you'll have to harvest like crazy, but the neighbors will love you for giving them all the extras.
Sixty-four years later: How Watson and Crick did it
1 day ago in The Curious Wavefunction