this looks like maybe a dwarf huckleberry bush. at first the leaves reminded me of a gardenia leaf, but I just started looking at small bushes that berry once in awhile, and run across certain leaf patterns and compaired a few. this is what I came up with. I hope it helps.

Maybe a pyracantha?

Looks like cotoneaster to me.

I think pyracantha, too.

If it's a pyracantha, be glad you have it in a pot. I planted one in my yard but it went crazy. I eventually got rid of it. The berries were pretty though!

Looks like a bush, not a tree. I think if you want it to get bigger you need to get it out of that pot. Its either a bayberry or pyracantha.

I believe it is in the citrus family. All citrus have thorns maybe lemon or orange tree.

looks a lot like a quince but I've never seen a white one.

I vote for pyracantha, too. I don't think quince has berries, at least, mine doesn't.

The leaves are too big for it to be a bayberry.

We call that wild olive. It has tiny white blooms and then small berries. It can be invasive. Leave it in the pot!

Marvin, I try to keep all of my plants. When one doesn't do as well as I thought I put it in the "graveyard" Put your plant there & see what it wants to be. Many of mine have turned out really nice.

How about a Wigelia bush

Are the leaves fuzzy grey on the back? Where are you?

the leaves really look like these

Oh I didn't read the berry part before, trying to think of shrubs I know it looks so familiar.

Might be a bougainvillaea, looks just like one in my green house in fact!

Nope not a bougainvillaea, no berries. Sorry. Pyrcantha variety.

azalea?

Pyracantha coccinea are evergreen,and do not die back in the winter. However P. koidzumii are evergreen to semi-evergreen, they are not as hardy, zone 8-10. Birds enjoy the berries during the fall and winter. Weigela does not produce berries. Flowering Quince produces small apple like fruit, has thorns and some cultivars have white blooms. They are deciduous woody plants. How big is the container and has the plant been in the same one all this time? My old eyes can not see the foliage good enough to make a proper guess as to the ID of this plant.

The first thing that came to mind when I saw your picture was "Crown of Thorns" aka Pyracantha!! I'm in agreement w/Judy W. Shirley J. &Diane B. on that. The berries that Evelyn R. shows look like Pyracantha - kind of a bright orangish-red. My Mom & Dad had one planted beside the chimney and it was HUmongous so I'd either repot it and give it a little more room or put it outside where it'll have lots of room but not close to your house or any other trees or shrubs. Keep it pruned or it will take over.

I have to agree, Pyracantha ,I have one and it grows fast [down south].

If Pyracantha the white flowers should have turned into bright reddish-orange very showy berries on a long clustered branch. I used in my fall floral arrangement-magnificant, and my Bassett hound ate them as they dropped of bush-non-toxic as far as I know. Here in our area,Northern calif, been berries since Nov-very showy against fence/snow etc. Horrible to prune, they do grow kind of wild and spreading if in ground.

Oh yes Marvin, you're going to have to wait for the berries! Don't forget to post it then. :)