I don'r know what it is, but I have it planted in a corner bed where I don't care if it speads - somewhat. It spreads slowly in my garden, but is a tangle of roots when I have to pull any out.

Western swordfern, Polystichum munitum, is a clumper, not a spreader. Fronds look similar - many ferns do - but they will all emerge from a single crown.

Possibly Polypodium californicum. That is a rhizomatous spreader and a CA native species.

Thanks, everyone!! I am going to be yanking a good bit of it out, so I guess when I do, I'll post some more pictures of the bottoms, and then maybe we will know for sure what it is.

I wouldn't mind it, but it is trying to get under the foundation - uh oh. After we got so much rain last winter, Nature has been really trying to take over just a little too much around here. I just need better boundaries! No illusion as to which is in charge. ; )

Maybe I will stick the bits in a pot. I do like a tough fern. I adore the look, but I've killed a bunch of container ones and I never buy them anymore. I wonder how this will do in a pot.

Oh, also ... does anyone know, how do I prevent future spreadings? Or do I need the id first? It's going under a deck ... it's kind of going all over.

Mine never spread much because my garden was dry. When needed I would grab a bunch at the base and pull it up. Can you limit water in that area?

Emmarene9, I can try - except for when it rains.