Front of leaf.

Back of leaf.

Ostrich fern? It's the only fern(s) I have and like the proverbial saying goes if you only have a hammer everything looks like a nail. Ostrich is a prolific spreader and will crop up in unexpected places. I rather like them, but will dig them up to thin.

This looks like it wants to spread through the whole bed.

TY, that last pic took literally like 10 minutes to upload, while you were posting. If you have a fern that spreads, that's all I need to know. This may not be the same thing, but it's got to go.

Dig deep - all the little "fernlings" see to be connected to the big one and just digging the crowns won't do it.

Luckily, I have a spot where they've been allowed to do their thing - by the time they start their die back, they're 4 feet tall. Quite lovely in a prehistoric sort of way.

TYVM! I'm definitely evicting this plant.

Lovely. Itôs a Phegopteris hexagonoptera.

Rgds

Always glad to get a name from someone who knows. Looked it up and found, too, that it grows from a "creeping rootstock" and that it can/might/will gradually fill in a garden spot. (Wiki)

Would love to have such a beautiful fern in my garden! It's too bad you don't want it in yours....

That isn't Phegopteris hexagonoptera

I have an invasive fern, its great in pots. None of my friends ever has to buy their spikes.

Definitely NOT ostrich fern, as that fern does not produce sporangia on the underside of the leaves but sends up a separate fertile stalk.