So, is this ok to put my seeds directly to big a pot after germinating, or do I need to put them into a smaller pot and later transplant them? Is 25 cm/25 cm/30cm square pot big enough for 80 cm tall plant?
It is better to put seedlings in a smaller pot and then work up to the larger pots. I think a 25 cm pot is a bit small for a 2 foot tall plant. For that one I would go a 2-5 gallon pot, 5 gallon being optimal.
As Smkn said start small and work your way up to the larger container. You will end up with a thick massave root system. BIGGER ROOTS=BIGGER BUDS. choke with ya later...
after the first real set of leaves i put em into somthin a little bigger, I usually let em go almost root bound in a 1.5 gal pot through veg then go big (3-5gal) a few daze BEFORE they go to bloom ....
so it is like that: germinating -> small pot -> big pot -> lots of pot? But what if I put two of those 25 cm square pots on top of each other thus doubleing the size?
Double potting works but IMO repoting all together gives better results and the double pot should just be used If your budding and need to add more room to root...choke with ya later