Also, the first set of leaves were a lot more ferny than the current set.

I think I'd start by looking in the Apiaceae. Those carrot-like seed leaves are pretty unusual and distinctive. It isn’t mountain ash or sumac, as you know.

Is it truly as acaulescent as it appears from the photo? Does the foliage have a fragrance when crushed?

Hello, macranthos. I thought you’d left us. How’s the baby botanist?

Ben, Mountain Ash did cross my mind, but the celery-like stem and thick textured leaves, and carrot - like seed leaves rule that out. Floral, I'm thinking Apiaceae too, but I have no idea what species. It looks pretty cool whatever it is. I am starting some Apiaceae species from seed, but this plant is nothing like any of the species I sowed. It could have been carried in on the wind, deposited by an animal, hitchhiked in a bag of seeds, or been in the potting mix. The only Apiaceae plant around here that looks close would be the introduced wild parsnip, Patrick sativa, but the leaves on my seedling seem already thicker than those of a full grown parsnip. Mac, I crushed a leaf and there was no scent, other than it smelled fresh, perhaps it's moisture on my dry nose. It seems to definitely have succulent, juicy, Apiaceae stems. I'm going to repot it and see what unfolds. Luckily there were a few Gentiana andrewsii seedlings that germinated also. This thing is growing like it's on steroids.

Interesting -- I thought it was two separate plants, but now looks like different type leaves out of the same base?

There's been a taxon change. My autocorrect has reclassified Pastinaca sativa as Patrick sativa. Yes the first set of leaves is totally different from the newer leaves. It's probably one of several native Apiaceae that I've sown seeds for in the past.

Potted up. This plant doesn't look like any of the Apiaceae I run into in prairies and woodlands. Maybe a wetland, moist soil species?

Your mention of Sium suave jogged my memory. That has variable leaves and they can be ferny. And it’s a damp lover.

Yes, it's Sium sauve. I've been trying to start it from seed for a long time.

What a lovely little meadow plant you've got. Glad you figured it out.

Floral, I did take a hiatus: covid just put too much stress into the house and I couldn't even bring myself to do this. But things are sort of lightening, so I figured I'd come back part time... maybe Mondays and Thursdays sort of thing :-) Baby is doing well. She's almost 3 by now and talking up a storm. Still loves to look at the flowers, but now enjoys throwing rocks in the stream even more.

Good to hear things are calming down. I find this to be a relaxant rather than the opposite...

Say hi to Mini Macranthos. Give her the Latin names now while she‘s like a sponge and they're no effort to learn. 😉