Nyssa sylvatica? Not a CO native, though.

After doing some research, it could possibly be sand cherry (Prunus pumila var besseyi).

This post was edited by Elektron on Fri, Nov 7, 14 at 2:56

Are those leaves alternate on the stem? Or are they opposite and one part fell off?

Thanks for taking a look. I was thinking that some kind of fruit tree would be the obvious answer because there are very few native trees here in the plains of eastern Colorado, but many planted ornamental apple, plum, cherry, pear trees. I will look up the sand cherry.

I was also wondering if it was missing some leaves. When I feel the stem now, there is only one rough spot (leaf scar?) at each node so I think it is alternate.

It seems like so few trees are in opposite arrangement and the ones that are often have very distinctive leaves like maples? When leaves are compound that makes things more confusing. I think this is a little tree?

Here is a link that might be useful: List of american trees with opposite leaves

I'm thinking amelanchier but I don't know what species it might be

Yes I think Amelanchier (serviceberry) is a good possibility. There are some planted in a park a couple blocks away. I took another look and Im pretty sure the leaves are alternate, the buds are much bigger than I remember from last week, here is a close up of them, you can also see that the stem is hairy.

The green leaf behind is from another tree and is included just to help me take the pic.

This post was edited by olreader on Fri, Nov 7, 14 at 14:09