A method of and system for optimizing a tree to meet timing constraints inserts buffers at selected ones of the internal nodes of a tree to form a plurality of subtrees. The method sizes the wires of the subtrees according to a wire code for each subtree, wherein each wire of a subtree has the same wire code. The buffers are inserted and the wires are sized such that slack along the path from a single source node to each sink node of the tree is equal to or greater than zero.