Leave it in dappled shade for the rest of the year.
I've always considered a seedling to be a plant in its first year. Sapling I use to
refer to a second-year plant (or older) that is still a whip or relatively skinny/unbranched.

I've had luck digging up a maple - root-ball and all - and then slipping the whole thing into
a container of bark. In late winter, I wash the old soil away and re-pot in a fast-draining mix.
The transition is painless and easy.

Josh

p.s. Were there large Maples in the area?

Josh

"Any tips on how to increase its survival chances? "

Pots are all about the soil/roots.

Keep them from drying out. Keep them from getting water logged. Keep them from baking in the sun. Keep them from freezing this winter.

Do you have a permanent home for it picked out? I have good luck planting the smallest trees in my yard and protecting them by inserting a large tomato cage with a wire fence around it. This seems to keep the rabbits and weed eater away.

Thanks for the replies - Josh, I saw pictures of your saplings in another thread, that gives me hope that this one'll survive!

We're using this baby tree as a "Unity Tree" in our wedding ceremony - my parents and her parents are bringing water from our hometowns, which we'll pour in the pot on our wedding day. Then we plan to keep the little guy potted but in the ground for the first five years or so, digging it up and repotting it every spring. We're doing this because we only plan to stay in our next house for ~5 years, and we don't want to leave our wedding tree behind. At the new place, we'll pick out a place to plant it.

Toronado, I'll try the tomato cage when we plant it this fall, and for the first year or two.

In the immediate vicinity where we dug it up, in addition to some other species (including Poplar, I think), there were about a hundred other maple seedlings growing, 20 maple trees I'm guessing were about 3-5 years old (~1-inch diameter trunk), a dozen maple trees about 10-20 years old (~6-inch diameter trunk), and a couple really old guys, with trunks of a foot or more diameter. Those are guesses on the ages...

I am worried that it might be waterlogged - it drains okay, but there's been a fair amount of rain lately. The soil it was growing in is fairly compact - to improve drainage, do you recommend aerating it somehow from top to bottom, with a shish kebab skewer or something of the like? Or is that a silly thing to try?

That's a cool idea for the wedding tree!

In that case, I'd recommend that you keep the tree in a container until you can put it in the ground.
In late winter, you'll want to remove it from the pot, prune the roots, and replace the potting mix.
You'll do this every year or two, until the tree is in the ground.

If the soil is holding too much water, try a wick:
use a synthetic thread, like a shoe-string or a string from a mop-head, and push it through one of the
drainholes into the mix. Let it dangle below the pot, and the water will travel down and out. This will
guarantee that there is no perched water.

Josh