Serrated

That photo on the front is one of the leaves of the cherry. I had never realised quite how very serrated the edges were.

I had a look at the hazel and saw a very different pattern.

Really, I should compare this hazel with elm leaves as they have a similar shape...

Back to the cherry and, for the first time in twenty-odd years, it has produced a cherry. What made it decide to do that?

There seem to be various possible reasons, but this one seems the most likely to me:

Successful Cross-Pollination: Many ornamental cherries are technically self-sterile, meaning they need pollen from a different type of cherry tree to produce fruit. A neighboring, newly blooming tree or a new swarm of bees may have provided the necessary cross-pollination.

A similar revelation with the acer. I had never noticed it produce keys before.

In this tree's case, the reason may be less encouraging:

If your Acer is suddenly full of keys, it is likely either fully matured, experiencing significant environmental stress, or it is a "masting" year.