rhizome control through plant guild

I'll start this topic off with a specific question for the group.

My Mil (mother in law) has a well established bush of Euphorbia amygdaloides var. robbiae, aka Mrs. Robb's Bonnet, and it propagates through a tenacious rhizome that will send out new shoots as far as 6 feet away from the original bush. The reading I find on the internet seems to praise it for it's full shade AND full sun tolerances, deer resistance, and low maintenance. On the flip side, it has a highly toxic sap when cut or broken and the low maintenance they speak of seems to neglect the fact that pulling the annoying shoots can be a real chore for anyone not wanting a monoculture of the thing.
My question, in studying plant guilds, what would be the most natural way to limit the rhizome's growth? To put it another way, is there a good companion plant(s) to make a barrier so that the plant can stay in one place and just look pretty? Any particular root type that stops rhizomes from progressing any further?

Any help would be greatly appreciated!

My 2 cents may not be quite what you want to hear... but I would suggest a physical barrier to block these roots, since it is only one plant.

As I understand it, a key aspect of a barrier of other plants to block the spread would usually be shading out/outcompeting the new growth as it arises. This might this not work on a plant touted for full shade tolerance, and it would use up quite a bit of space compared to a mechanical barrier. I'm not aware of a plant that would block the roots more directly...

If these rhizomes are prone to diving under obstructions, the barrier may not be such an easy thing, though.

Does this plant have upsides other than hardiness? Maybe removal is an option, to get the hassle over with?


Hopefully someone with experience with this particular plant will have a more specific suggestion for you!

My Mil loves the plant for ornamental reasons and it definitely is a good pollinator, considering I'm attempting to incorporate this into a plant guild. I've heard the plant's sap may work as an astringent but I haven't found much to back that statement.
Beyond that, a physical barrier may be the only way although I was hoping for something that could outcompete the rhizomes. As for barriers, I would imagine that it has to be deep because I've seen these shoots pop out of the middle terrace wall that helps makes my Mil's garden level. We're talking at least a foot deep or more.