Hello everyone,

This small tree (probably ~15' tall) is growing in Cheyenne, Wyoming, in the hospital's landscaping. When the flowers opened, they were creamy-yellow. The tree's form and palmate leaves remind me of what we call Ohio Buckeye, but I notice the leaflets on this this tree are much narrower. Does anyone know?

Thank you!

Could very well be Ohio Buckeye - Aesculus glabra - but could also be some other Aesculus species growing far from home. The growing conditions in Cheyenne, WY don't exactly match up well with eastern North America where Ohio Buckeye is native to, so altered leaf morphology could be expected in those generally drier conditions in the high country.

If you can take more pictures of the whole plant, then trunk, branches, etc. then perhaps we could offer a more solid opinion of this plant. Also, since it appears to have flowered well, stay with the observations and take pictures as seed begins to form where the flowers were. The characteristics of the reproductive parts are also good for determining which species you have there.

Thank you John. I'm starting to wonder if I just happened to pick a branch of Aesculus glabra when the leaves were juvenile/newly emerged. The third pic kind of supports that theory Sorry about the fire drill!

Those last two pictures of the trunk and basal flare offer interesting information.

It appears that this could be a grafted plant. If so, it is far more likely that you could have an Aesculus hippocastanum (European Horsechestnut) selection there.

It would have been great to see that plant in full flower. You captured images just before the flowers opened, and then these after-flowering pictures with seed forming.

Aesculus hippocastanum 'Baumannii' has double white flowers, quite distinctive from the native species of Buckeye. Also: you can separate most/all the non-North American Aesculus species by their sticky buds. Check for that next time you stroll by this specimen.

Well, this is getting interesting. Various sites show A. hippocastanum with more ovoid leaflets than those of A. glabra.

https://www.uwgb.edu/biodivers...
https://www.extension.umn.edu/...

I'll try to keep a better eye on the tree and watch for the fruits to mature later this year. Thank you for your help!

You are quite welcome.

A couple more pictures of a seed I managed to pick. A helpful clue? Thank you!

It looks like a Horse Chestnut (Aesculus hippocastanum). There are a lot of them growing here in northern Nevada and southern Idaho. Very cold hearty and very pretty.

Thank you Daisy!

I agree with Daisy's summation.

Aesculus hippocastanum - European Horse-chestnut - is a non-native Buckeye equivalent. That quite spiny husk helps identify it, and separates this species from most of the North American species.

Did you remember to check the parent plant for sticky buds? That's another good way to ID, even when no leaves, flowers, fruit, or husks are evident.

Watch it next spring when it is in flower. I won't be surprised if you report that it has double flowers, since it appears to be a grafted plant.

Thank you John. I'll watch for the buds and blooms next year. I haven't been able to check the parent for sticky buds, as the grounds keepers trimmed all the suckering shoots. The branches are pretty much beyond my reach, and I had to jump several times to pick the seed I did get

I sowed the one seed in a pot outside. Perhaps it'll germinate come spring (though I'm not expecting it to come true to 'Baumannii'). Hmmm. I just read on the Missouri Botanical Garden site that 'Baumannii' doesn't set seed. Maybe there's another double-flowered cultivar that does set seed.

Thanks ever so much everyone!

Just to close the loop, here are pics of the seedling when it first germinated and with its first leaves. My camera has a hard time focusing on white and light yellow, but hopefully the last photo is clear enough to give an idea of how the flowers look.

You still owe us a picture of the buds. Even if you can't reach them, you should be able to zoom in on one or several, and the evidence will be there. Additionally, that seedling will have buds as it goes into dormancy this fall.

Those are normal flowers for the genus Aesculus. If the parent tree is indeed Aesculus hippocastanum (or even 'Baumannii'), then the seedling will exhibit similar traits though double-flowered selections don't always produce double-flowered seedlings.