https://www.thespruce.com/solomons-seal-1402856

Beverly, I'd read this article previously but didn't find anything about thinning. Am I missing something?

That certainly does look unnatural! It normally creeps about on its rhizmes. My guess is whoever planted it didn’t want it to do that so put some sort of buried restraint around it. The only way to find out for sure is to dig around it and look. And then decide whether you want to continue to restrict it or not. If you want to still restrict it, divide it to be a smaller clump and discard or give away the excess. The best time to have done the digging and division would have been early spring as it was emerging, but if you wait until after the flowers fade and if you don’t mind risking losing a bit of it, you could still try it - if the weather is very hot, it might be best to wait until it cools down in lare summer/early fall.

Welcome to the world of culling. Live with it through the season and come fall should it still torment you, go through the clumps and cull appropriately. Next season see if you like your handiwork; repeat as necessary.

Sounds like I missed the boat for this season on culling. Will it do any damage if I just cut at the base of the stem now and do an apprpriate fall division?

IMO digging it up and seeing if it is unaturally contained is best to do in the fall and at that time you could slpit the clump and have more that one clump in the garden It also would be good to post pics of the whole garden and gardens evolve so being careful to respect what has been done is still living thing that over times needs to be changed . I like SS in spaces under trees like in nature .

Oddly enough, and contrary to most traditional info about Solomon's Seal, my mother grew a big patch on a slight slope in full, all-day sun, and in quite dry soil, and thereafter ignored it except for admiring the beauty. This was back in the 1950s continuing for decades. I took some when I finally had a place of my own, and (being the word' champion procrastinator that I have always been) just tossed the clump on the gravel drive in half-day full sun. It is still there, untouched, after 25 years. Still manages to be beautiful, and has increased.

I also plunked some of that out back where it gets more shade but is in very wet soil (vernal swamp out there). Both patches are flourishing, despite my neglect. (The patch on the driveway gets buried by the snow plowing every winter, yet manages to rise every spring.)

I don’t think there would be a problem cutting down some stems now - they might grow back by the Fall….! I don’t know whether Solomon’s Seal sawflies cause a problem in your area or not. Here, by mid-late July a lot of stems have yellow leaves that are shredded by the sawfly larvae. I cut those stems to the ground and discard them in the garbage. That never seems to damage the plants - i.e. they all return next spring as vigorously as ever, so cutting down some stems likely wouldn’t hurt it but I’d probably wait until after they have finished flowering just to be cautious.