In message , Jo
writes
Whilst looking at a neighbour's pink blossom tree today I noticed that one
very large thick branch had produced white blossom of a completely different
shape and size to the pink blooms on all the other branches. A bit of a
mystery. Can anyone explain how this can happen?

Explanation 1: the white blossom is from the rootstock.

Explanation 2: the white blossom is a sport.
--
Stewart Robert Hinsley