To pare back to a more reasonable growth, do I rip the newer growth out? Do I pare back to the original plant? Can I use Roundup, selectively, on the shoots and, if so, how much of the plant will survive?
I'm leaning on the last option because this plant is really, really hearty.
If you are in the Midwest, I suggest cut the “stringy” shoots back to make a hedged bush about 3-4 feet tall and 3 feet around.
We’ve planted mint around outbuildings. It seems to discourage pests of all sorts. HOWEVER, we did this knowing it was invasive. Hubby keeps it in check with the mower and weed eater. It smells like mint juleps when he mows that part of the yard.
If you want to restart with your mint you could try rooting it from cuttings, once those are established in pots, kill the ‘mother’ plant and then transplant the rooted cuttings only this time keep them IN their pots. And put them someplace you can easily keep them in check with the mower or weed eater.
Just my 0.02.
I try not to use things like round up, because one of the reasons I started growing my own food was to avoid pesticide exposure.
Mint can become invasive, and I usually just grow mine in a pot, or would at least surround it with edging, and pull everything that appears outside the edging.
So it depends on you and your tastes. You could even just dig up the plant and put it in a pot and pull out all the rest of the shoots and plant something else.
I even keep the catnip in planters for that very reason.
/johnny
Mint needs to be grown in containers because it is very invasive and spreads like weeds. Dig out what you don’t want so you get the roots.