Why we strip the bottom off or, 'lollipop' it? That is because once the plant fills in up top , particularly if you have multiple plants under one light, it is very difficult for the full intensity of the light to reach down near the base of the stem.
There is some light penetration considered sufficient but iirc it is only about 1 to 1.5' with the most powerful of lights; 600 and 1000 watts. I would think CFL's, led and weaker HPS bulbs have far less penetration than a 600 or 1000 watt HPS.
Those leaves and buds not getting the full intensity of the light are not going to be at their full potential, leaving you with fan leaves not being productive and fluffy light buds that dry out in cure to nothingness or chafe.
The tighter you keep the prune to where the nodes are condensed the more easily the full intensity of the light will hit all of the buds. Between physically pruning to keep all the bud nodes condensed at the top and the intense direct light; You wind up with big, fat, dense buds covered in crystals that are all very well and evenly developed when it comes time for harvest.
If you like to have some variety in your bag, you leave maybe one spaced out node below each fat cola. This is the stage I'm on, deciding how dense, or close to the cola I want to prune. I'll post a pic of how close I am currently. I got the LST down pretty good but I have a feeling the pruning part is going to mostly come with a experience and having a feel for whatever strain is currently being grown.
Incidentally, keeping the low hanging vegetation pruned off allows for far more air circulation at soil level. This from what I've read is beneficial for the plant in allowing more airflow to the soil and reduces the chances of getting parasites, insects, mold, algae etc...
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