I've been doing some research on "scrog" & just want some confirmation. OK my babies are about 5" tall about 3weeks old. When should I start tucking them under the net? & my most important question, I know that by tucking the top that I'm encouraging her to grow horizontally, but will this create multiple tops per plant? I really need some help guys, thanks.
Most people, from what I've seen, start scrogging once they flower. Since marijuana stretches 2-3 times it's vegged height, doing it in veg isn't very productive. If anything, tying your plant down, LST, would be a good idea to keep the plants short. Combine that with topping, and you'd have a pretty nice amount of tops! Best idea would be to top your plants, so you have a ton of tops to grow up through the screen.
The idea of a scrog is to grow your plant up to and then underneath a screen in order to achieve an even canopy and distribution of light. Someone who is experienced in the scrog method might wait until they flower to start but it is not advisable. A good route is to place your screen 8-12" above your medium depending on your space and your light another 8-12" above that depending on your lighting. It isn't required to top your plant but topping it once can help with even growth while training under the screen. Basically what you want to do is allow the plant to grow up to the screen. As it starts growing through it you bend the branches back down underneath so they grow along the bottom side of the screen in an as even pattern as you can make them. When your screen is 60-70% full you will want to flip the lights and your plant should fill the screen before it is in full bloom. It can get quite humid and stale underneath so it is also advisable to do some minor pruning where there is no light to open up air space and allow the plant to breath, otherwise it can be an inviting environment for molds and funguses. Anyway I hope this helped you a little, if you need more information just do a quick search there are lots of great threads on this subject. I will try to answer any questions you might have tho.