Posted: 24/07/2012 at 10:58
Julieh, Salix or Willow is a tree and depending on which of the 500 odd types it is can grow quite large though some do manage in pots.
Very wet or very dry conditions can cause leaves to discolour and buds to die back, there could also be something nibbling at the root ball.
Whatever it is needs looking at so if possible drop the plant out of the pot and look at the roots, it may need a bigger pot, if so pot it on, check it is not water logged, see if there are any wee creatures in there. See if you can get the pot into a bit of shade, not full shade but probably out of the mid-day sun, (mad dogs and Englishmen, the only things that like it).
I lost my quite old Willow to Honey fungus, they do seem prone to it although you would smell it if it had that problem.
Leaving it may work but we gardeners usually cannot abide a mystery and most would investigate, looking at the root ball in a pot is usually the first thing we do.
Hope all is well when you check often it may come down to a bit of feed and a little more water although I doubt that this year.