I am growing lettuce for the first time in. I have harvested a few lettuce leaves and the plant is now flowering. The flowers have been for around 20 days now. I wanted to save he seeds from this plant. Could some one suggest the right time to harvest the seeds.
The fluffy stuff (puffs of white cotton) is ready for harvest, they are attached to the plant very mildly when ready. If you take the fluffy stuff and it lets go/ detaches they are ready. In nature they will be taken by the wind to find a new spot to grow next year, so be sure to be one step ahead of the wind.
After reading Giacomo's comment (thanks!), I want to add that the best way to harvest is to take the whole head off the plant. After a while the fluffy part will be detach from the seeds, see here for a good instruction about the harvest.