Seeding lettuce. The leaves are no longer bunched close to the ground, but start to spread out upward as vertical stems with flowers (seeds) grow. (It was described to me as looking like a “Christmas tree”.)
I also learned that carrots are biennials, meaning that in the first year they use their energy to make the roots (carrots) and then use their energy in the second year to make seeds. In the second year, the carrots would taste very bitter because the plant’s energy (sugars) are diverted to flower and seed production. This means that a farmer would need to choose whether to grow the carrot plant for food or for seeds; he couldn’t get both from the same plant.