I bought a very well flowering wisteria standard last year and after a lot of tender care and the obligatory pruning in summer and winter it has produced masses of spurs this year. However, they are only just about to start to come into flower and I have noticed that the spurs are dropping the individual buds en mass. The wisteria is planted in a large pot, under planted by a couple of bulbs and wood anemones. It's living in a sunny spot with occasional dappled shade. What should I do?