Solved Is this a weed?

I have been nurturing this plant for the past few months. I thought it was a delphinium or geranium! What is it?

 

Buttercup?

 

A fine buttercup. Very nice. Post it to me if you don’t want it.

 

Uh gheeezz! It had me fooled!

 

That looks like a very fine Meadow Buttercup rather than the annoying Creeping Buttercup.
Ranunculus acris | meadow buttercup Herbaceous Perennial/RHS Gardening

 

I did exactly the same some years ago.
I had planted some delphiniums in that area and slugs had the lot.
Then a brand new one seemed to appear close by - it turned out to be the same buttercup as you have

 

That's the kind of plant that gives a little colour when you lawn is burnt to a crisp in the middle of summer - if we get one. I'm happy to leave them in my grassy patch.