there is more to that. one tree for regrowth and one for nourish.
the one for regrowth takes all +crit talents from balance and resto trees. add living seed to it and balance talent that reduces casting time by 0.5 after crit. + glyph of regrowth and u have 1.5 sec cast that leaves living seed in 70% of casts, with glyph effect that oncreases healing done by 20%.
the one for nourish takes all talents reducing mana cost of nourish and increasing its healing to have standard spam spell.
well maybe im wrong, maybe one of those is clearly better than other, i didnt make any theorycrafting but thats how i see it