The life cycle of auto flowering cannabis.
Another common question I see is when to switch autos from veg to bloom. Many people are under the impression that as soon as they see the first flowers it's time to switch. Perhaps a little explanation of the life cycle of autos will help to clarify this.
Weeks 1 - 3. Once you've started your seeds and they break the surface of the soil, they are in their seedling stage. The first set of leaves to appear will usually single fingered, followed by a second set that may still be single fingered or perhaps 3 fingered. Once that second set appears growth will start to accelerate as the new leaves provide more photosynthesis. This process will continue, more new leaves, faster growth. Depending on the type of soil in use, mild vegetative nutes can be introduced at week 2. By week 3 most plants will start to show their sex. Males will start to produce pollen sacks and females will display pistols.-
Weeks 4 - 6. The plants are now entering a pre flowering stage. During this time the plants should exhibit explosive growth, often as much as a new set of nodes and 1" vertical growth a day. This is the time when they will gain most of their vertical height. Many people make the mistake of switching from vegetative to flowering nutrients at this point, assuming that since they see flowers it must be the proper time. This is incorrect. If the switch to flowering nutes is made at this time the vertical growth will stop and the plant will put it's energy into producing buds. If you need to keep your plants small, or want them to finish earlier, they by all means switch nutes at this point. But if you want to get the most out of your plants continue feeding vegetative nutes until you see the vertical growth slow and stop. Depending on the strain that will usually be sometime during week 5 or 6.-
Weeks 7 - 9. By now vertical growth has stopped and the switch to flowering nutrients has been made. The buds will start to fill out and put on weight, becoming hard and tight. Pistols will start to change from white to brown, orange, red, etc. By now the plants will also have developed a strong smell. Toward the end of this phase the large primary and smaller secondary fan leaves will begin to turn yellow. This is an indication that the plant is moving toward the end of it's life.
Weeks 10 - 11. At this time flowering nutes should be discontinued and only plain pHed water fed to flush the remaining nutrients from the soil and improve the taste. Yellowing of the fan leaves will continue as the plant draws the stored energy from them. Eventually they will die and fall off. By the time that the smaller leaves that come from out of the buds will also start to turn yellow. Then it's time to harvest.-
Source:
https://www.420magazine.com/forums/frequently-asked-questions/243982-life-cycle-autoflowering-cannabis.html