In article ,
Jeff Layman wrote:

Are all the buds black (flower and leaves)? Frost won't damage wisteria
buds - they are very hardy. But if yours is grafted (as many are), it
is possible that water got into the graft, froze, expanded, and split
away the scion from the stock. Graft failure in wisteria is not uncommon.

It can, especially when they have started to open and the frost is
reasonably hard. I have lost most of a year's flowers that way.
They didn't go black, merely shrivelled and eventually dropped off.
But that was all. It sulked for a bit, and then grew normally.
My understanding is that most established wisteria came through
1962-3 with a loss of a year's flowers and some setback - but, in
that year, there wasn't a frost AFTER they had started growing.

You have a good point about grafts - I loathe the things, and the
few grafted plants I have cause an excessive amount of trouble.


Regards,
Nick Maclaren.