I have a bourbon shrub rose "Boule de Neige" which is in a large pot.
Last year it flowered beautifully but this year buds start developing
normally then instead of opening they shrivel up and form a ball. The
petals themselves seem to get stunted and shrink and shrivel before
they get to a size where they should open. They don't even try to
open. It happened with every single bud. Has anyone got any
suggestions as to how to manage this please?