Right but as it's liked to the pop shouldn't we wait till we have westros to do that so that it actually has a meaningful impact? Because we would need a shit ton of trees to do that as our current lands has much lower pop than westros.
Starting the program early, allow us to build confidence in it early, if the Westerosi have stories, about our citizens giving blood at the trees to no ill effect, then they're more likely to do it themselves.
Also a secondary plan I'm considering with these trees, is to see if we can get Danelle to endorse them as a valid form of charity, on one hand the Seven wont like it because it's blood sacrifice, but it inflict no permanent damage, and the profits go to creating healers, who will heal everyone rich or poor, so they're probably pretty much the perfect instrument, for getting the Seven to lighten up their stance, that all blood magic is evil, and having a Chosen of the Seven endorse a program, to raise funds for the creation of old god loyal beings, should work as part of the reparations, we need to get the old gods from the Seven.
And the longer she has to observe the good the Blood donation program does, before we ask her to speak in favor of it to the Faithful, the bigger the chance we can convince her to agree, therefore I want to set up the first tree now, as if the blood donation program has already paid for dozens of healers, and those healers have saved lives, then the fact that the program is a proven force of good, make it more likely that our epic diplomancer skills, can overcome her disgust with blood sacrifice in any form.
And it's not just linked to pop anyway, it's linked to pop, and to in how many places we have blood donation trees, 1-2 trees can accept all sacrifices for a city, but people only have time to make sacrifices to local trees, so if they don't live around a tree, they can't participate.