I’m not the only half-assed gardener in the Back Forty (inches), my little plot of backyard concrete. The wind, the birds, and the squirrels have been known to plant things as well.
In a weeding mind, I over-zealously pulled this out of a pot:
Oops, hello, sapling! The seed here looks like a hazelnut or a hickory nut: 
But that can’t be right because of these leaves, which say “oak” to me: 
But what kind?
Of course, I may be barking up the wrong sapling entirely. I’ve transplanted it to its own pot, so let’s see what becomes of it.
UPDATE 6/14: We think this is probably a pin oak (Q. palustris). Unfortunately, I returned from a weekend away to find the sapling dethroned from its pot, lying wilted on the ground. The seed was atop of the soil. What happened? It turns out that there’s another growing in a different pot amid some annuals. Stay tuned.
Hi Matthew – Definitely an oak of the “red” inclination. Too hard to tell yet, we’ll have to wait and see! Thanks for the tour of Prospect Park today. As the Victorians would say, “T’was fun!”
- Marielle
I’m going to guess a Pinoak.
Pin oaks certainly are the local type. The street out front is lined with them.
Paul,
Just passed a pin oak on the street. It was spouting a few small leaves down on the trunk, and they looked much like these; very different from the narrow, deeply lobed leaves of the mature tree.