The American Elm can be confused with two other species of elm, The Slippery Elm and the Siberian Elm. Luckily, the American Elm can be easily distinguished from these two when it is bloom— as it happens to be right now (in Indiana). So if you’re unsure about a particular tree, now’s the time to check!
American Elm flowers are pendulous, they hang from stalks about half an inch long, which get even longer after pollination. The other two species have flowers without stalks or very short stalks. It’s as simple as that.
Don’t confuse the anther and filament (the pollinating part sticking out of the flower), for the stalk. Here’s another comparison
If elms in your area don’t happen to be in flower right now, another thing that can help is looking at the buds. American Elm buds are orangey brown, and relatively hairless.
The other two elms have more of a purple/grey color scheme going.
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