What do you mean, "should I keep it?" You already yanked it out!

Geographic location?

I am in Southern California. I pulled it out of the container for my roses and transferred it to another pot. It looks pretty hardy so I think it will survive. Just need to find out what it is and how to care for it!

It looks like it is emerging from a largish seed pod or nut, so probably not a Prunus. And the fact it is growing from a container and likely buried there by a squirrel would lend some credence to it being a nut tree seedling.

I don't know much about Californian trees but how about almond? Just a guess, it does look like a prunus and that nut does look like an almond. Or it could be some completely different subtropical tree that I haven't even heard of

That was such a good point. Now that you mentioned, I remember having to fill up a hole there a few months ago dug up by some animal. I looked up black walnut trees. The leaves look similar, but their nuts don't have a smooth skin like the seed I saw.

Carya illinoinensis (Pecan)

Agree w/ Bill... it's a pecan seedling

Thank you so much! I looked up pictures online and that's exactly what it is. Now that I know it's a pecan plant and may grow to be over 60 feet, I'd better find a new and bigger home for it!

I've never seen a Pecan tree or seedling. At what age do the leaves become pinnate?

Don't know when that feature occurs. Referred to as 'oddly pinnate' for some reason.

Here's a link to pecan info.

According to sources, they grow very well in SoCal.

Oddly as opposed to opposite I presume. Synonymous with alternately pinnate. But the pictures I looked at were oppositely pinnate. As is the pic at your link. Weird....