Well, probably the most common advanced growing technique that's not general practice amongst weed growers, would have to be the '
Autumn Colour Effect' or the '
ACE' technique, as I like to call it. This is where the Nitrogen is cut off from a flowering plant in mid to late flowering (depending on phenotype) so that the plant extracts all the remaining Nitrogen from it's leaves and puts it into the bud, this hugely reduces chlorophyll level in the plants leaves and buds by the time the plant is finished [which aids with good tasting, good burning weed] (cannabis, being an annual, does not require Nitrogen for the final leg of flowering, having to take it up, process it and motabilize it, hinders it's ability to put all its strength into the flowering process.
To use the Autumn Colour Effect (ACE) to its full potential, you have to really know the pheno you're growing (having grown clones of it multiple times) so you know how long it takes to finish, what it likes/dislikes, what it can or can't handle etc.
This is a common technique amongst
elite growers (not the elite on this site that pay for that status, the true elite, like those who showed me it - and I was sus at first but they proved its benefits too me with out too much difficulty ... Mind you a 10,000 Watt grow is
very impressive to any grower when they're reasonably new to the scene.
Too do the ACE technique properly you have to grow Soiless or Hydro, or any other system where you have control over which nutrients the plants do or don't receive at which time during the grow.
3 weeks away from harvest (previous grow):