There are varying opinions on both the benefits and drawbacks of pruning cannabis. This website presents information from the perspective of “what’s the easiest and cheapest way to put up – and maintain – an effective personal grow closet?”, only some general insights can be offered.
Since healthy sun leaves are the photosynthetic “engine” powering the plant’s functions, it would seem reasonable to believe that removing too many of them would somehow disrupt a plant’s genetically pre-programmed growth plan. Recent observations suggest there’s a discernible link between a developing bud and fan leaves attached at the same node. Trimming cannabis fan leaves immediately beneath the flowering buds seem to slow their growth rate, and possible ultimate yield.
On the other hand, there can be some practical reasons to prune your plants. Upper leaves can block light from lower leaves and buds, so you may want to selectively prune several back. Leaves on plants growing too closely together can block out each other’s light, so a little thinning may be in order there, too.
It’s always a good idea to remove any diseased or dead leaves from the plants. If they detach from the stem with just the slightest tug, then they weren’t serving any productive purpose for the plant and needed to come off.
The concept of pruning lower leaves to concentrate the plant’s growing power upwards has some merit, but again, it comes at the cost of reducing bud development on the plants’ lower stems. Benefits may also vary by genetic strain and other factors. Most growers simply experiment until they find what they think is the optimum setup for themselves.
There still doesn’t appear to be any consensus on the pros and cons of topping your plants. Cutting off the growing tip of a plant to produce two growing tips instead is thought to double the number of colas produced per plant. Scientific views, though, suggest that a plant’s ultimate yield is already pre-determined by its genetic blueprint. Producing two colas instead of one by topping does work, but the plant’s DNA won’t let itself grow colas as large as before, making it appear to be a zero-sum game. Again, personal experimentation using sensible control methods will probably provide you with the best insight.
