I have a peculiar problem with an apple tree in my backyard. As you might be able to tell from the picture below, it's only flowering on one side. That's not too weird if it weren't for the fact that last year it did the same, but on the exact opposite side. And all the years before that it just bloomed normally. The flowers aren't also just distributed on specific branches. Both times the flowers seem to choose branches at random as long it's on the side of the tree that blooms. If that branch goes to the other side it simply doesn't bear any flowers over there.
My father, who planted the tree, says it's around 20 years old and that it's of the 'golden' species. We didn't do anything special to the tree nor did we do any building work, soil management or other alteration to the surroundings in the last two years.
Would anyone be able to shed light on this? While I have searched, but I haven't found any information that can clarify this so far.