The cotton plant can tell us a lot about what has happened and what is coming if we know what to look for. Some basic notes to take in a cotton field are: total nodes on the plant, node of first square, and the number of squares present and abscised.
When the plants first emerge, they tend to grow slowly. However, once the plant has 4-5 true leaves, it will add new leaves (nodes) every 3 (2-5) days or 50 heat units.
When squares are missing on the plant and cotton fleahoppers are suspected to be the cause, count the number of nodes between the missing square and the pinhead sized square. If a node is added every 3 days and there are 4 nodes between the missing square and the pinhead square, the square was lost at least 12 days ago. This result is because a cotton fleahopper injures squares smaller than a pinhead.
The first bloom on a plant usually occurs when the plant has 9 nodes above the first position white flower. To determine the time until bloom, count the number of nodes above the first square to the uppermost mainstem unfurled leaf (1-inch width). Subtract this from 9 and multiply by 3 and you have an approximate number of days until bloom. If the plant has 10 nodes and the first square is on the 6th node, there are 4 nodes above the first square. Subtract 4 from 9 and multiply difference (5) by 3. There should be about 15 days to bloom.
More information on how the plant grows can be found at the National Cotton Council website HERE.
A good article was written plant growth regulators can be found HERE.