The 40/60 Phenomena are events observed during the indoor cultivation of flowering cannabis, and when using a strict 12 hour inductive photoperiod (aka 12/12). The events start with the first day of the inductive stage (12/12), and end on the day a mature crop is ready for harvest, collectively this period of time is called the Days Spent Flowering.
The stretch phase is a period of time during early flowering where rapid extraordinary outward growth takes place. Some growers have reported seeing 5 inches of growth in a single day during the stretch. This phase is characterized first by the extraordinary growth accompanied by longer than usual internodes, then the explosive outward growth slowly tapers off as internodes shorten. The end of the phase is signaled when growth tapers down to approximately 1/2 inch or less per day. This coincides with a time span equaling 40% of the total Days Spent Flowering. At this point growth shifts from outward to building bulk on existing growth, otherwise known as late flowering or the fattening phase.
The last 60% of the inductive phase is a period where outward growth is less significant. In fact, it can appear as if growth has stopped completely due to the very short internodes. During this phase a more complex set of growth activities occur. It's not much different from an apple tree that stopped producing new apples and is now devoting its remaining time to maturing or ripening the apples it already has. With female cannabis, flower production accelerates, floral clusters begin to grow wider or fatten, resin production increases and peaks, sinsemilla calyxes plump, pistils start to wither and change color, and not long after that the plant is ready for harvest.
How To Use The Phenomena
The time-table of the stretch and fatten phases are important events for cultivators growing an unknown variety for the first time. The two most common anxieties for indoor growers during flowering of an untested variety are....
An indoor grower with limited space, especially limited headroom, can find his plants pressing against hot lights if he doesn't take measures to plan for the explosive growth that takes place during the stretch phase. Knowing how long the stretch will last can give him that advantage. Similarly, a grower with limited time doesn't want to wait until the show is over to know when it will end. There are many things he may want to do with his time now that it's freed up from the high maintenance demands of extraordinarily fast growing plants during the stretch. Having an idea whether this period of lower maintenance will extend another 40, 60, 80, or ??? days will also help in the timely scheduling of his next crop.
The 40/60 phenomena relate to two milestones.
When one of those two flowering events are known, the other two can be predicted.
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