I thought spanning trees were elected/discovered automatically by the routers themselves instead of being manually set up.
The tree is built up automatically but you can weight the paths and also which is the start node of the tree. There are also a lot of settings that may or may not completely fuck you over or fix a problem.
Also you really want to disable STP on ports going to servers as this will 1) speed up recovery 2) prevent any malicious packets going out from them.