That's pretty neat stuff. I was just thinking that's a lot of trouble to go to. I guess we all have our challenges. Here in Colorado, it is hot sun, dry wind, and clay soil. Where you are, it is hungry, burrowing, rodents.

I found them but wasn't willing to pay a buck each, so I make them out of hardware cloth.

That should spoil the little demons tunneling. Good show!

I would not even think of planting a hosta or daylilly without a hardware cloth cylinder. We also top dress the root ball zone inside the cylinder with PermaTil so the voles can't simply dig straight down into the crown.

That is a great idea about the permatill!

PermaTill- it says available on Amazon but a search doesn't bring it up and of course no where here in the boonies carries it.

Sharp gravel would likely work the same way.