Pflanzen Runterbinden

I'm afraid the plants will hermie if I tie them down after switching to 12-12. So should I stop at the latest by the third week after the switch, or is it better to stop earlier? The flowering sites are only very slight so far.

Stop all training by the end of the third week of flowering, otherwise tie/bend/train as much as you want. After this it becomes very difficult for the plant to redirect flower growth direction.

Timing -- so your previously top cola evens up with all the axillary growth before 'vege' growth ends (3 weeks into bloom or longer in some cases). It breaks apical dominance.. so how that impacts the plant you are looking at should dictate timing. One that branches easily won't need as much time for the axillary growth to catch up. Those tall lanky plants might be a bitch and near impossible to have the intended impact, if you do it late. My durban poison diary has a 'tall lanky' pheno. i was very surprised at the even buds across canopy based on early growth and difficulty to make it branch out more. I had it tied down from mature vege (was a clone of unknown age). tried to make sure when i released the top cola allowing it to grow vertically that it would roughly be equal to others in height. That top cola will quickly regain dominance on its own. vertical height is important.. the more even it is the more even distribution of resources and growth will occur. There's no one-size-fits-all method because there's potentially large differences in growth patterns.