Gardengal is correct. It isn't a fern at all but an anemone, which is an ephemeral spring wildflower. The leaves are similar so I can understand your mistake. A very desirable woodland flower, it can make a lovely picture on the woods floor in spring but it completely disappers shortly after blooming, to return next early spring. Maidenhairs don't come up until late April or early May depending on where you live. They have tiny threadlike fiddleheads and wiry black stems, can get to about 2' tall. Sandy

I've tried growing these things in my house before and they are indeed finicky. They need substantial humidity to thrive--have you done anything to supplement humidity where it's growing? I've also never understood that ice cube thing; I've heard about it being done with orchids and didn't get it. We're trying to provide conditions as close to the plant's native habitat as possible to get it to thrive, and I'm sure these plants don't receive an incredibly slow trickle of icy water in their tropical homes. Usually watering with lukewarm water is recommended because some plants are sensitive to cold water. As long as you're watering it thoroughly enough that water comes out the drainage holes and the soil is saturated throughout, you shouldn't need to also do the ice cube thing :)

I think this convo spurred me to try again, and I got an Adiantum aleuticum 'Imbricatum', and it apparently likes where I planted it (outside..not a house plant), and still has nearly perfect fronds (mild winter), we shall see. They are lovely...though the challenge for me may be the wetness of early to mid spring for it. The planting location is on the north side of the house, and it gets shaded by a growth of mimulus alatus (winged monkey flower) and it came through summer fantastically. I hope to see spore spread in a year or two, shield fern, lady fern, and painted ferns have performed well for me here and spread along the house foundation area.

You would need a pretty good sized terrarium but that does provide a beneficial environment. Otherwise, they like much the same conditions as most other indoor ferns: a free-draining but moisture retentive soil like the 5-1-1 mix, indirect light, warm temps (house temp fine) and reasonable humidity. Just never let the soil dry out excessively.