How long until I can swith to flower?

hello mate, you are more than ready to start the flowering phase. I advice you to prune the lower part of the plant to have more energy in the part with more light exposure but don't overdo it. Good luck and happy journey!!

for my part when i grow photo i like to have a more even canopy before flipping to flower. i will suggest to defoliate the top main stem to slow it down and give the time to the side branch to reach up.

It says your plant is 40cm in the diary, if you flip now then it could finish up at 80cm or more after the stretch. It could even stretch past 1meter. If you don't have much height in the tent then flip sooner rather then later.

It will double or triple in size after you switch to 12/12 flower cycle. So, when it fills roughly half your area that your light covers appropriately under 12 hours of operation. Might want to strip some lower secondary branches - especially ones in more congested areas -- with the imagination of future growth the next 3-4 weeks before it stops. Remove an axillary bud or secondary stem, but leave as many fan leaves as possible. The plant knows better than us when it needs to shed leaves.

heyho, i would switch to 12/12 i dont know, how much space you have left but depends on the strain, they will stretch alot. your diarie said 40cm already and RQS description says indoor 60-100cm For the future, you can affect growth with distance of your lamps and even with the spectrum like more blue more bushy more red more stretch in veg

Really up to you how long you want to keep vegging for. I reckon you could flip now. She’s looking very healthy and happy. She will also stretch a bit in the first three weeks of flowering.