we actually plant ours horizontally with a gradual curve from the start. not sure if it has the same effect as it does later. but, its the way my dad did it. he probably got the technique from my grandpa who owned a greenhouse. no clue. i do know that i think the plants tend to be more flexible when young and you also probably get the lateral rooting started earlier too. but, i am also guessing if right away was the way to do it, the professionals you see in the above video would be doing that too.