Ohio is the Buckeye State. The Ohio buckeye that is native there must be very special. Perhaps all other trees that are native to Ohio are just not very uninteresting. Whatever the situation, I sort of believe that the Ohio buckeye is more appealing in some regards than the California buckeye that is native here. However, the California buckeye might be more weirdly interesting.
The main reason that California buckeye is not popularly used in landscapes is that it is ‘twice deciduous’. That means exactly what it sounds like. Just like other deciduous trees, it defoliates in response to cooling autumn weather, and refoliates in response to warming spring weather. Unlike other deciduous trees, it repeats the process through the warmest weather of summer.
When summer weather gets too warm and arid, the foliage of California buckeye shrivels and sort of defoliates. Without rain to dislodge the shedding foliage, it can linger and look shabby for quite a while and maybe until it is replaced by secondary foliage that develops as the weather mellows. The secondary foliage does not last long before it is time to defoliate again for autumn!
California buckeye is not often planted into landscapes because it really does look like the living dead through summer. It provides no shade when shade is most desirable. Those that I work with are only here in the landscapes because they grew from self sown seed that sneaked in on its own. Some will be subordinated to more desirable adjacent trees, although there is no rush.
I happen to like California buckeye. Except for the rarely seen red horsechestnut, it is the only species of buckeye that I am familiar with. Bloom is neither colorful nor reliably profuse, but is delightfully fragrant in close proximity. Not many natives are fragrant.
Tony Tomeo 
Never heard of it and so I had a look in Internet. It seems it is really something from America and there seem to be no species growing in Europe. Something else I have learned. It looks very pretty.
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The red horsechestnut might have been one that you could have seen in London a long time ago. It is rare here, but English clients sometimes request them, as if it is a popular tree in England, particularly as a street tree in London and urban areas. English interns (studying arboriculture) know what it is.
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That is odd that it loses its leaves twice. I wonder how many are cut down because they look dead.
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It is why I am subordinating one of mine to the camellias and oak around it. I happen to like it, but it is in a public place where it is not very pretty in about August. As the camellias fill in, and more of the buckeye gets cut back, it will eventually get removed completely.
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Interesting. I has a buckeye in the backyard at the mansion in Mississippi with AWESOME red flowers. I should have saved seed and brought them with me.
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It made seed?! The showiest of the red blooming buckeyes are red horsechestnut, Aesculus X carnea, which is a hybrid that makes no seed. Yours must have been a straight species that blooms red. Aesculus pavia is the red buckeye, that is native to the region.
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Yes. I identified it as Aesculus pavia. It was short like a shrub instead of a tree.
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That is how Aesculus californica is. It eventually gets rather tall where shaded in a forest, but prefers to be an understory tree.
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My wife is a native Buckeye, so be careful what you say about Ohio. Buckeye flowers can be quite beautiful. The nuts, called conkers, and inedible – but useful for throwing at your brother.
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The buckeyes here are not as appealing as other buckeyes. I happen to like them because they are familiar. However, it is obvious why those who are familiar with the genus might be disappointed with them. There is a European buckeye hybrid of some sort that makes a nicely complaisant and fruitless (or nutless) street tree. I believe that it is the red horsechestnut, Aesculus X carnea. It really should be more popular than it is here.
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