I bought some about 40 years ago at a small feed store, in Southern California; they were locally fairly common there/then, so thought nothing of leaving them behind when we moved to Oregon.
Never saw any again, until we bought our ‘temporary’ house in SD, where we lived on visits & then moved into full time, until the ranch house was ready to move into.
That house had 2 patches—one reds, and one yellows— of them in the yard, and having learned my lesson, we dug a couple of hundred, and planted them here.
Now a couple of neighbors have some started; and I sent a batch to Justadumbblonde a couple of years ago. She thought she had killed them, but I doubt she’s capable of that, unless she has a nuke squirreled away in a barn.
From (other) forum posts, they seem to be slightly more common in Britain. They do not flower, so do not produce seed; they only propagate by division.
Are those the kind Territorial has?