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.
Growing Sunflowers. Sunflowers grow fast and only last a single season. After planting the seeds, sunflowers take two and a half to three months to mature for harvest. After the flowers develop, they slowly turn downward away from the sun as the seeds mature. You can tell it's harvest time when the back of the seed heads turn from green to yellow.