Fast flowering strain takes long to start flowering.

like the first ansawer

No such thing as 'fast flowering' ... Still takes 8-10 weeks for most of them to flower - a fast photo or auto might take 7 weeks, but it's going to be rare and certainly not consistently so without clones of a rare plant. It's a false perception that autoflowers are somehow faster in flower phase than photoperiods. It's only possible to come to that conclusion measuring from the taint on one and not the other. People are comparing a time frame counted accurately (when light schedule changes) to visible signs on an autoflower that takes 7-10 days for form and was in flower long before the human eye could discern. 'fast flowering' plants that incorporate ruderalis genetics are just weakening the genetics without the trait of automatically flowering without a change in light schedule. It's a worse product depending on poor perceptions of consumers to make it popular.