If you sowed directly, you will not have the need to transplant and therefore, your plant runs less risk of dying once it passes from the 15 days of life.
From this moment you must keep the constant irrigation (once every three days) and the light conditions, but if the temperature is greater than 30 degrees Celsius in the afternoon, it will be best to look for half shade. The same applies with extreme cold: if where you live the temperature descends below zero at night, you must wait for the conditions to be more tempered to harvest your lettuce successfully.
Lettuce harvest
With the passage of time, you will see how the leaves take the typical form of lettuce depending on their species; However, although your plant seems completely ready to eat before, you must Wait for at least three months After sowing to harvest them.
Before doing it, irrigate the previous day and make it the first hour of the day or once the sun is falling.
Cut the leaves of the most carefully attached to the ground (preferably with sterilized scissors) to allow the smallest to continue growing and you can use them later or, if you need more lettuce, arrace it from the root to use it complete after disinfecting it.
Repeat the process with the seeds to have this permanent vegetables in your homecultivated by yourself.