ive heard 75-80 is best for optimal growth... my plants usually stay right around 76ish.. idk how low is too low..? i know they can go pretty low tho and be ok.. thats actually how a lot of people get their plants to turn purple.. cuz if the temps are too cold.. the stem starts turnin purple.. and eventually.. the bud starts to turn purple as well. some people drop the temps purposely to make their plants turn purple.. i heard it has to be about 20 degree drop in temps at night for it to turn purple....
idk exactly wat page.. but in my journal in the begining. maybe like page 2-7 or somewhere around there.. a kid posted pics up of his White Widow.. and it was purple.. he did it purposely. he was the one who told me if you drop the temps enough it will purple.. just a cool tip for u guys... i havent done it yet.. adn i dont know how low it too low.. soo dont go droppin the temps to like 30 degrees.. and freeze ur plants and then get pissed at me. lmao.. oo yea. and i just remembered.. my last grow.. temps got around 63-65 at night.. and they were fine.. they didnt have any problems.. soo 65 is ok. =) hope this helped