A friend of mine was telling me that if you give a plant 24 hours of light for the last few days of flowering before you harvest, it causes the plant to produce extra amounts of THC... anyone know if this is true?
Not true! It is actually 24hrs of darkness that will trigger an increase in THC. Light actually destroys the crystal, thats why it is important to harvest at the right time, when the crystals are mostly clear and only a few have turned brown, they are at their peak for THC content, once they start to turn brown the THC levels decrease. good luck. PS. you will need a good magnifying glass!
also in eds book it says to crop just before the end of the plants dark cycle on 12-12 as this is when the thc is at its highest...