Good questions Sue. I'm still working out why a root chomping critter would confine himself to a 3 x 3 foot space. Knowing what you saw when you dug up your plant and some photos would be helpful.

Daisy

Well, you made a nice bed of soft soil and mulch for something to make tunnels! Every time we would mulch, the voles would go "woo hoo!" and then have lots of babies. They have around 7 each time, several times a year. (I'm only mentioning the non-striped underground hamsters because that's what I've dealt with in the past.)

Could you maybe take a photo of the hole, and show it relative to the plant, or get something else in the photo with it so we could tell the size of the hole? That would help narrow down what could be burrowing. And then a photo of the bed too would be great.

It would be helpful to see the area of the yard in question. A few images of any holes as well.