Second attempt.

       I've written this all once and it was as if "Publish" actually read "Vanish".  It started as "Lessons in Larch".  NOT that it is Larch, it just closely resembles; its Sunday name is Cedrus Atlantica Glauca Pendula (Now then - there's a gob-full).
       It was its resemblance to larch which caused my wondering - how do side twigs form? 
       NO doubt I'll be corrected - BUT - it seems that - Towards the top there's an army of micro Shaving Brushes marching down the stem.  They appear to get longer, over time as needles drop & are replaced.  Eventually, lower down the pic., side twigs appear; and so it goes on?