When it starts to warm up, usually over 75°F lettuce plants like to bolt aka go to flower. Once it bolts the lettuce is typically more bitter and tough and not so great to eat, often times people will pull it out and use the space to replant. If you let the lettuce do its thing you have a chance to collect seeds for your next growing season. It will bloom flowers that pollinators love and then just like a dandelion it will close up and reopen with the little white fuzzies. As soon as they do this it is time to collect! You will be amazed at how many seeds each flower head contains. I just snipped off every little flower head with the fuzzies and brought them in side to seperate. You’ll want to make sure you spread them out and let then dry before long term storage. Store them in a cool dry place or in the freezer for a more extended “shelf life”.