Importance of the Tree in Saddle Fitting
IMPORTANCE OF THE TREE. Because the tree is rigid, it spreads the weight of the rider over the whole of the contact area of the saddle.
Everything else that makes up the saddle is merely a soft coating of leather and padding. So the fit of the saddle relies almost completely on the shape of the tree and of that fitting well.
The core of every saddle is the tree (except for treeless saddles of course). Every saddler makes, or buys, trees that have different widths at the wither (no doubt the most important area of fitting on the horse). The best of saddlers will have many differently shaped trees so that he or she can take account of the shape of the rest of the horse's back. For the saddle to be truly comfortable, this must happen. If the tree does not follow the whole shape of the horse's back, the stuffing of the saddle, which may initially seem to fit, will change shape and mould itself to the shape of the tree within it. It does not mould itself to the shape of the horse. Before long this saddle will become uncomfortable and, possibly, painful for the horse.