Pruning greenhouse cannabis is generally done for two important reasons: increasing airflow throughout the canopy and base of the plants, and removing excess foilage to increase light absorption and reduce wasted energy. Once in flowering, the plants will retain a bit more moisture than in growth stages, so maintaining an airy, open nature at the base is important for mold and disease prevention.
1. Focus on Hygiene
Hygiene? Yes, hygiene. It is extremely important that employees who prune and trim maintain clean and sterilized instruments. Isopropyl alcohol can be used to sanitize tools between cuttings and different blocks of plants. Tools used for greenhouse cultivation should not be used outside, as it could introduce pests or disease into the controlled environment. Hygiene refers to the plants, too, so always remove any yellowing or dying leaves when you spot them.
2. Hit Those 45-Degree Angles
Making razor-sharp, 45-degree angle cuts at the base of the stem or branch keeps vapor and humidity from having a fixed landing area. Over pruning, such as removing upwards of a quarter of the total amount of branches or healthy leaves at one time, is discouraged, so be strategic with your trimming and pruning scheduling.
3. Pruning is a Systematic Process
Pruning is generally a four-stage process, starting five days into the vegetative phase when plants are very young (focus on yellowing growth) and culminating with a final prune before bud set in which only growth that will survive harvest and form the final colas will be left. Focus your initial prune on the lower 25% of the plant, and the secondary prune on the lower 50%, training the plant to its final canopy structure.
Source: Solaris Farms Pruning SOP/Michael Sassano