I have only had it in my herb bed a few years and no problem with it coming up else where.
I got my start from my mom who has had a patch for years 15+ and it gets bigger but does not roam or reseed as far as I can tell.
How old is your patch?
I grate the cleaned and pealed root put it in a jar and add some salt , just a little , and vinegar. I use just a small amount for preserving but you can use more . Keep it refrigerated . If you make small batches and use them I prefer to just add a bit of oil and skip the vinegar. Beware it is super strong and may make you have breathing problems when processing.