Fortunately, there are several methods for limiting rose of Sharon's habit of rampant self-seeding.
It's also possible that you might want to grow some rose of Sharon plants into mature specimens. If so, the ease with which these plants self-seed also makes them very easy to propagate intentionally.
To read more: https://www.thespruce.com/get-rid-of-rose-of-sharon-seedlings-2132694