The autoflower vegetative phase.
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 nutrients can be introduced at week 2. Some autoflowers will already display pistils.
Find this video on youtube: Time-lapse autoflower weed vegging (vegetative phase)
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 nutrients 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 nutrients at this point. But if you want to get the most out of your plants continue feeding vegetative nutrients until you see the vertical growth slow and stop. Depending on the strain that will usually be sometime during week 5 or 6.