You're absolutely correct joey. The chemical changes that occur throughout maturation influence the "type" of high. Earlyier harvests "within" the
window of maturity produce a more "heady" sativa type high, while later harvests, which allow more THC to break down into CBD or CDN, give a more narcotic, body
stone.
When to harvest<-link
There are several important points to consider when choosing the optimum time to harvest your marijuana crop. There are different factors to consider between indoor and outdoor marijuana plants. There is the difference between Sativas and Indicas in bloom duration and final effect.
There is the difference between early and late harvest to encourage head to body high respectively. There is the issue of chemistry because what we are really considering in terms of the ripeness relates directly to the chemical nature and state of the plant at harvest.
Calyx swelling is a major indicator of peak maturity. The lowest, oldest calyxes swell first and the swelling works its way up to the highest, youngest flowers on each bud. At peak maturity about 90% of the calyxes will almost look seeded, they are so fat.
Three quarters to 90% of the pistils will have turned reddish brown as well. For a basic Indica this takes well into the seventh week of the flowering cycle.
By the end of the eighth week most of the calyxes will have swollen and a surge of trichome development has coated most of the buds. It is now that the development of a very discerning palate comes into play to determine the finest harvest time. Remember - patience is a virtue and often a discipline.
The ripening signs for most Sativas are highly similar, except extended over a longer period of time. Occasionally, some Sativas have windows of peak harvest that actually open and close. That is, for a week or so the plant may exhibit signs of peak ripeness.