I don't know that it's possible to declare a "ready" lettuce size! It depends on the variety, the weather, etc.

I pay attention to leaf-size -- when leaf-lettuce has enough good-sized leaves to pick from the outside, that's when I harvest those. Some people harvest lettuce when it's small, some when it's large (no real information there, I know!) Romaine lettuce is taller and the leaves are usually wider, though they do fine if you harvest the outside leaves first, too. Come again another day to harvest the next batch.

Another good clue is pretty simple. Just look at the seed package or vendor sites that have pictures of the variety, and see what they look like! Then look for the lettuce-height, which is usually given. That's as close as you'll get!

The leaf lettuce that I had this year was a red leaf variety and the leaves, at maturity, were a good 12 inches across. Of course, I think lettuce is always ready. I pick 'um young. I pick 'um big. I pick 'um all. But when I pick them, I always leave a few leaves (or several if they are still small) and the plant will give more.

Steve

IMHO, the smaller the leaves, the tastier they are. So pick whenever youwant. :)

Since with leaf lettuce I only pick the outside leaves, my rule of thumb is if I can get a salad out of my lettuce without picking so many leaves off the plants that they're going to go into shock, it's ready. Early in the season I might get one salad a week, by the end I'm getting a great salad every day. That's with 6 plants.

when the outside leaves get to 4 inches or so go for it. if you cut them and leave the rest of the plant they will produce lettuce for a long time. if you are pulling up the whole plant then it may take longer. me, as soon as i can cut off enough greens for a salad i am going to! smaller leaves are very tender and so delicious!!! hope you have a great dressing for them.

Depends on variety and how good the conditions are. My rule is that I should pick them before the plant bolts. Of course, by the time the plant bolts it's too late (or rather, it is merely "late", because I pick them and eat them anyway, but no one else in the house will because by then they're bitter - the lettuce, not the family members). For black seeded simpson, one of the most common leaf lettuces, I like them about 3-5" long. Any longer and I have to tear them into a lot of pieces and any shorter they're hard to handle while I wash them. It's really a matter of preference.

I've never cared if I killed the plants either. Lettuce season is always so short anyway that by the time the plants are big enough to eat, I only have a week or two to eat them before they bolt. Maybe other folks are using other varieties or shade cloths or something like that.

It is actually a good question.
I do not cut off the whole head, even for Romaine, as some people do.
Here is my calculation: I can start taking leaves from the time that the plant can be viable without them.

That means that until they "get going", say, with 4 leaves spread out and photosynthesizing, I leave them alone entirely. If they are going strong, I take more leaves. If I want bigger leaves, I let them go a few days. If I have too many plants, I particularly abuse them. The weak ones will die.. so what. Eventually, they get so strong that you can take all but two or three leaves, and they will keep going based on what their roots are doing.

Size depends on the variety, so that advice would not do you much good. Just take as much as you want without killing the plant, and don't be too shy. Lettuce is actually pretty tough. I have it growing out of cracks in the sidewalk.

Thank you, everyone; I realize it was one of those "are you KIDDING me?!" type of questions, but I seriously didn't know when to pick it.

Subsistence farmers where I grew up started picking it quite small like the "baby greens" salads in bags at the supermarket. They would sometimes broadcast surplus old seed, often mixed lettuce, spinach, beets, turnips, collards etc. The lettuce would germinate and grow fast and be harvested first, quite tiny.

I pick mine at about 6 inches long for romaine and loose leaf. I only pick the outside. I have picked my lettuce about 8 times on the same plant and they are still good. Even picked bare, they will continue to leaf if you leave the stalk unharmed. Just keep picking the biggest outside leaves until it starts to get bitter from heat.

Thanks for your "idiot question" i was wondering the same thing

Thank you for asking this! I had no idea either!!

Hi, Everyone I live in AZ where it's hot hot hot and for the first time I'm growing a garden ..I want to thank everyone for answering the gentleman questions for when to pull lettuce because I didn't know either Ted answered it all because my lettuce is being over powered by the squash that's next to it ..Thanks Ted ...

D