fastest ive got to harvest was diesel ryder...sexed at 12 days old harvested on day 57...you dont get a huge yeild...but you get a pretty fast harvest of some dank bud....autos will have the shorter flowering time...even if you go 12/12 some strains can take 2+ months just to flower..on average 7-10 weeks for most strains.some sativa strains taking way longer than that..where some auto strains can have a flowering time of 6 weeks...beginning flower at 2 weeks...so in about 2 months some autos can be harvested