The Natural Philosopher wrote:
Some varieties will self seed - crabs especially.
Nice blossom, poor fruit.

My parents had a crab apple in their garden along with
a range of other apple trees. At the end of a really
good summer, if you looked carefully, there were some
that had gone very red and could even be sweet enough
to eat (or nibble, at least). But mostly they just went
into making vast quantities of crab apple jelly.

#Paul