Chemical Weathering. Chemical weathering takes place in almost all types of rocks. Smaller rocks are more susceptible, however, because they have a greater amount of surface area. Chemical reactions break down the bonds holding the rocks together, causing them to fall apart, forming smaller and smaller pieces.
Autos generally are ready to harvest sooner than photoperiod. Most autos are ready to harvest 65-90 days after being sprouted from seed. Some super autos have been bred to grow very big and can take up to 100 days before harvest.
The leaves become bitter and the plants begin to bolt as the stem elongates into a tall bloom stalk. Leaf lettuce varieties take about 40 days from seeding to harvest while head types may take 70 days. This is another reason the head types are more of a challenge. To get more from your garden space, consider interplanting your lettuce with slower maturing crops.