P91109KCalifornia flora is remarkable. It all does what it must to live comfortably in every ecosystem, climate and geographical region here.

California horsechestnut or California buckeye, Aesculus californica, is one of the more unusual native species. It is so in tune with the climate that it makes other deciduous trees seem to be inexperienced. Of course, to those who are unfamiliar with it, it just looks dead right now.

In chaparral climates of California, some deciduous trees start to defoliate early, before the weather starts to get cool in autumn. California sycamores, for example, can start to defoliate late in summer if the weather gets too warm and dry for them to want to hold their foliage any later. Such defoliation is more the result of minimal humidity than the result of chill.

California horsechestnut takes this technique one step further, by shedding spring foliage even earlier in summer, then refoliating once the rain starts in autumn, and then defoliating again as the late autumn foliage succumbs to frost through winter. It is ‘twice-deciduous’. It is a weird process that should not work, but obviously does.

It seems like a tree that is defoliated most of the time would exhaust its resources and wear itself out. However, California horsechestnut somehow stores enough resources to produce weirdly big seeds. These in the picture above are the same that were featured in ‘Six on Saturday‘ last week, while they were still in their husks.

Squirrels might chew on a few of these seeds, but do not bother storing them. They are mostly ignored by wildlife, perhaps because of their objectionable flavor. So, without squirrels to bury them, they fall to the forest floor near the trees that produce them, where they are too bulky to sift through the detritus to reach the soil below.

It makes one wonder why they put so much of their limited resources into seeds that are too big to reach the soil, but unappealing to wildlife that might otherwise disperse and bury them.

They know what they are doing.

Once the rain starts, and the seed sense that the weather is damp, they germinate on the surface of the detritus on the forest floor, and extend their tap roots through the detritus to the soil below. The seeds are too bulky to reach the soil directly, but contain all that their primary tap roots need to survive without desiccation until they reach the damp soil.



25 thoughts on “Buckeye

  1. Facsinating stuff Tony. I grow other forms of chestnuts/buckeyes in my garden in western France [ hotter and dryer summers than most other northern european areas – up to 35C and no rain for weeks on end- and cold and wetter winters – down to minus 10/12C – and there’s hardly been a day without rain since the end of Sept. I have noticed that all species are very early to lose their leaves, [even the “indigenous” ones] and they look “stressed” even when other apparently “similar” trees are somehow holding onto their foliage. But I’ve never seen any of them resprout. What a brilliant bit of evolutionary response!

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    1. It makes sense for the climate where most of this species live, but does not work so well in landscapes. I happen to appreciate when a landscape designer composes a landscape of natives (or at least cultivars of natives), but the buckeye does not go over too well. It looks great in spring, and blooms nicely, but really looks shabby as the spring foliage deteriorates. When it stops looking shabby, it looks dead.
      There is at least one nice specimen in a riparian situation here that retains spring foliage through summer, until it gets replaced by autumn foliage, but it is none too pretty about doing so.


    1. Oh, that is weird, but it makes sense. (It is weird too that a Ficus would get only one embryo from only two per individual fruit.) Coconuts are designed to float long distances too, but (I believe) are still ungerminated for the process.

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  2. There are so many behaviors, qualities, etc. in nature that just seem inexplicable. This is another one to add to the list, and it’s really interesting. There’s magic all around, and so much of it goes unseen.

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    1. For this species, it seems like there should be easier options for getting their seeds into the ground. I can’t argue though. They are out there doing what they do, and doing it well.


    1. Yes, it is interesting. As an arborist, I often explain that taproots are overrated, and that not many mature plants use them. Those that might use them in the wild probably do not use them in regularly irrigated landscape situation. (There is a misconception that all trees have huge taproots that are proportionate to the trees that they are associated with.) Buckeye not only uses a taproot to get started, but then develops lateral roots deep below grade, from the original taproot.

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  3. Your Buckeyes are indeed HUGE! Ours are black. I had a tree in the back yard of the mansion in Mississippi that had been consistently cut back and grew like a shrub. I really liked its flowers. I don’t think there are any buckeyes growing here on the farm. We have a lot of trees I don’t know, but I think I would recognize a buckeye by the flowers and fruit. Thanks for sharing.

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    1. These buckeyes are not easy to use well in a landscape. I would not plant them, but happened to leave two where they grew just because I could not find anything really wrong with them. They can be removed as other trees around them grow and want their space. Anyway, the bloom is nicely fragrant. Pollarding and coppicing would deprive them of their appealing branch structure, but would also make them even more vigorous. If ours were pollarded or coppiced, they might retain their first foliage until replaced by second foliage.

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    1. There are a few related species in North America, and some are prominent in their respective forests. (Ours in more of an understory tree.) Ohio is known as the Buckeye State for the Ohio buckeye (Aesculus glabra) and the common, yellow or sweet buckeye (Aesculus flava). I know our buckeyes are not aggressive within their ecosystem. When trees are cut down, there are no seed to replace them any time soon. Their seed do not get dispersed very far from parent trees. Each generation is only a few yards from the previous generation.

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  4. One Christmas I was given a box of candies called buckeye balls — balls of peanut butter dipped in chocolate. Having never lived in buckeye territory I didn’t understand the significance of the name, but without the chocolate they would have looked exactly like the featured photo above — thank you for the education 🙂 !

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    1. They sound like spherical peanut butter cups. Although buckeyes, or horse chestnuts, are toxic, they happen to resemble the unrelated chestnuts, which are made into traditional confections for Christmas.

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      1. Oh yes, and chestnuts are not easy to find here anymore. There are still a few trees remaining at the farm, but they are mostly dead, and producing only a few nuts for squirrels.

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