Is this Feverfew or a Fern?

There is also what appears to be a nasturtium there as well.

 

Yes those bits are remains of Erigeron karvinskianus. I chopped it all right back about a month ago when it had mostly stopped flowering, and I trim it regularly during the summer. I prefer to trim it rather than pull it out, as it happily grows back and flowers abundantly in the summer, and fills in the times when other things aren't flowering. The minute I stop trimming it in summer it gets covered in flowers. There was about a month around September when the Erigeron karvinskianus was flowering abundantly when other things weren't. I also use the Erigeron karvinskianus trimmings to soak in water that I use to protect other plants from aphids.

I do a similar thing with lobelia, I trim it back rather than pull it out at the end of the summer, and it grows vigorously again the following summer, acting like a perennial rather than annual. I find lobelia so difficult to grow from seed as you need a greenhouse to get its seeds going early enough, that I prefer to treat my lobelia like perennials.

 

Yes I have left a few nasturtiums, having trimmed them back and tidied up the yellowing leaves, and encouraged them to climb rather than take up space and light from other seasonal plants. Last year I had nasturtiums flowering on Christmas day, though they died back a lot and stopped flowering around late January and February, only to spring into life and flower again in March.

I haven't quite decided yet how much to trim back the nasturtiums, but they are still flowering and have plenty of flower buds.

I have seen bees and even hoverflies still enjoying the odd nasturtium flower, so if they provide the pollinators with what they need in winter they are worth keeping.

 

I stand by my original call. Dryopteris filix-mas, the male fern....I pull up loads of these each year

 

I think we'll have to wait until next May and more photos to reach a definitive id.