When the lighting is reduced to 12 or less from vegetative 18-24 hours, mimicking the short days of the late summer and fall, cannabis plants release hormones that begin the flowering process. The most explosive vegetative growth occurs the first two weeks of flowering, and when properly anticipated and planned for, that burst of energy can be channeled into an ideal flowering canopy.
As plants are introduced into flowering, they often need several days to adjust to the changes in temperature, humidity, light intensity, light spectrum, nutrient feed, and air movement. Additionally, the plants are inevitably jarred around quite a bit when being moved and it takes some days for them to stabilize and adjust the leaves and branches to optimal positioning for light exposure.
Trellis (plant netting) is a great choice for canopy support in most situations, with taller batches of strains sometime requiring two or even three layers. The initial, and lowest, is applied as soon as the plants begin flowering, and the primary branches should be carefully woven into the net, opening the plants away from their center, encouraging optimum light exposure to the nodes and no gaps in the canopy.
Visualizing the unleashed explosive early flower growth allows most effectively incorporating it into an even canopy with proper depth and structural strength. Each plant should be conceptualized as having a “spring” within them, with different genotypes responding with an early flower growth spurt that will vary. Some varieties with sativa dominant characteristics will grow triple their vertical size if allowed, while others with indica dominant growth patterns may not even double in size, but rather push that energy into developing a thicker, more robust structure and branches. Developing the ability to see “where the plant will end up” is vital to a proper canopy, and in return, yield. This theme should be a focus throughout the vegetative and early flowering stages.
Fan leafing is the practice of removing the large leaves that often block the light from reaching what would be otherwise productive flower sites. When implemented correctly, it can increase the productive depth of the canopy, allowing for increased yield. Without fan leafing, the lower flowers will either not grow at all due to lack of light, or will be too immature for use when the rest of the plant completes its flower cycle.
During the first few weeks of flower, its best to remove the fan leaves two or three times, as the leaves will quickly regenerate. I recommend removing the leaves on day five, 12, and 19 of flower, as the plants need at least five days to adjust and would not benefit from the additional stress of leaf removal prior. Removing the entire leaf isn’t necessary, if it isn’t blocking otherwise useful canopy. The goal is to see the light penetrate several feet into the plants; I often stick my hand into the lower areas to see how much light is reaching through.
Leaning several feet into the canopy with a small pair of scissors to deftly remove only the targeted leafs isn’t easy. It takes good vision, balance, and the ability to gently reach inner areas without bumping or breaking any branches, which will be naturally positioning themselves for maximum light exposure. This can be a physically grueling job, but well worth the effort when the bottom line is considered and labor costs assessed. In my experience, the price associated with fan leafing is outperformed by the additional product value.
Depending upon variety and structure, it can be beneficial to remove the fan leaves again seven to 10 days before harvest, giving the maturing flowers additional direct light. By then the fan leaves have done most of their work and are becoming inefficient to additional flower production. The removed fan leafs can be efficiently extracted with an isopropyl alcohol soak, and utilized in topical or edibles.
The continual evolution of understanding how a maximum yielding canopy appears visually, as well as how to achieve that desired result, takes the experience of seeing many crops grown to completion, as well as having accurate data to collaborate the assumed result. Even the most experienced gardener will always have those extra percentages of efficiencies to pursue, and along with plant health, genotype selection, and environmental control, canopy management is instrumental to a high yielding, low cost of goods garden.
By: Ben Burkhardt