We have not yet addressed yields because if you are at the third stage of floral maturity with fully form trichomes, then we will have to assume most strains have packed on all their final weight. Even then, there are variables but we can use the guide-lines spelled out below to help gauge the best harvest window for your plants based on the trichomes.
1. Fully formed but still clear will provide a cleaner up high with less sedative effect; this is the best window for heavy Indicas.
2. Fully formed and turning slightly cloudy or milky; this is probably the best time to pick most hybrids available today.
3. Fully formed completely cloudy or milky with at least thirty percent of the heads turning amber; this is usually best window for the late maturing Sativas such as Haze. This is also a good window when using the plant primarily for Hash production.
Take for instance the Jacks Cleaner harvested at fifty-six days; all trichomes are still visibly clear with very few turning cloudy. At this point it has a very up high and an in-the-head buzz. I get some good visuals and the lemon flavor is sour and a tad tart. The same plant, left just one more week at sixty-three days flower; the trichomes have turned milky white and a good portion, about thirty to fifty percent, are deep amber almost the color of cola. Taken at this time the smoke is heavy and thick, the lemon zing has been replaced with a musty sweet lemon smell that reminds me of Lemon Heads candy. The high is now all body high and very much a sedative. We would smoke this only as our night time medication. It is almost an example of a plant taken too late, however we do this because of the medicinal properties she takes-on at this late stage.
Another example is Killer Queen. At forty-nine days flower, she has a candy-like smell and taste with that same up high. If you were to harvest her at sixty days flower, she becomes Super Killer Queen, with a more skunk-like smell and a thicker trance-like high.
The mistake to try and avoid is harvesting before the trichomes are fully formed, so as mentioned in the guideline; most growers whom use this method, harvest at the point in which the majority of the heads are cloudy. Harvesting before this window will produce bud that is less potent, containing less essential oils and trepans, causing your finished stash to take on a grassy or green taste, even if it is dried and cured correctly.
Another good method would be harvesting some of the more mature buds, usually being the upper or main colas. This will allow more light to shine down on the lower portion of the plant, not only will the buds mature further but they will also pack on some extra size.
If you have a nice digital camera with a macro feature, try taking some close-up photos and use a photo editing program such as Adobe. This will allow you to zoom in close so you can see what the necked eye cannot see. If this is not an option, Radio Shack sells battery-powered hand-held microscopes for about fifteen dollars.
Take advantage of this information, it will help maximize the results of your favorite strain, or help you determine the harvest window of something new.