California Buckeye

Identification: When in leaf, buckeyes are hard to mistake: they are our only tree with opposite, palmately compound leaves (i.e. divided into 5 “finger” leaflets, like a palm, a hand). In leafless fall and winter, you can often still recognize them by their nicely rounded shape in open areas or more sprawling form in crowded canyon bottoms or creek sides. Except for a few gnarled ancients, most buckeyes have smooth, gray bark that is reasonably distinct from their likely neighbors. And most of the trees they share their habitat with are not deciduous, so once you know the community they aren’t hard to pick out among the ever leafy live oaks, bays, and madrones. In fall, you might also see their fruits even after the leaves fall: tough leathery pods that cling tenaciously to the tree for months.

Where: Buckeyes often join trees like coast live oak, bay, and madrone in “mixed evergreen forest” (it is generally not the dominant tree, but rather fills in the gaps, leaving the general appropriateness of the community’s “evergreen” moniker intact–it is the only one of those four that is deciduous). It often tends towards the relatively lower, moister areas of this landscape, including right along shady creeks. Buckeyes are common throughout Novato, Marin, and the Bay Area; you can see them in any of our woodland preserves. 

Appreciative Essay

or A Tree at Human Scale

The California buckeye is distinctive, easily recognized, and easily loved. More than a few novice tree lovers pick it out early on in their dendrological lives as somehow meriting a special affection. My own experience was no different. It can play several roles – from the embodiment of youth and freshness when the leaves unfold in early spring to the gnarled patriarch sculpted by time, and from the sprawling streamside filler-in to the picture of symmetry on an open hillside. But in whatever place it finds itself, the buckeye often seems kind of quirky and personable, more approachable than more grandiose trees, appropriately scaled for a more human give and take, for an easy meshing with our eyes, anatomy, and the places that make up the human habitat.

One of the gnarled patriarchs, this particular tree was planted at UC Berkeley’s Faculty Glade in 1882. Spiritual nourishment on a student-friendly budget: admire the buckeye, take in a free Wednesday noon concert at Hertz Hall next door, then take a walk over to the lovely English oak outside nearby Senior Hall. Photo by Carli Baker of the Daily Cal.

The originating source of this sense of convivial human-ness is most likely found in the form of the buckeye’s leaves: five leaflets, arranged palmately like a human hand. I think it is not surprising that we find this vaguely hand-like shape to have a certain subtle emotional appeal, something which inches it subconsciously closer to the category of “friend” and away from the category of “other.” Even our trees with palmately lobed leaves (maples and sycamores) share a little in this spirit, but among our trees only the buckeye truly divides its leaves into 5 (occasionally 7) entirely separate leaflets, accentuating and making their pentamerism more clearly fingerlike. When we go below tree height, I think many people find a similar attraction in the tiny hands of our lovely flowering lupines. And at the same time that buckeye leaves strongly recall hands, they go beyond the practical concessions of our opposable thumbs in order to maintain a perfect symmetry, which is probably innately appealing to us on another deep biological level.

New leaves, February at Indian Valley

And it is the moment of these leaves’ first appearance which will often imprint them so clearly in our memories. I can still bring to mind February visions, when on a cool, damp morning I descended a shady canyon to discover the year’s first unfolding of the buckeyes. One of the communities in which they feel at home is in the cool fellowship of streamside live oaks and bays, these more abundant trees providing the relevant appellation to what is commonly known as “mixed evergreen forest.” But amid these evergreens slowly gathering the wood’s weak filtered light all the year round, the buckeye stands a little apart as a tree who remembers seasons, who knows what it is to die and be reborn. And so when you enter into such a wood on a moist morning of earliest spring, with the wealth of flowers and summer birds yet to appear, and amid these skeletal scaffolds encounter the freshest of new leaves, opening like the hand of spring after months of winter absence, then buckeyes will suddenly seem like the most alive creatures in all this forest of impatiently contained vigor. The trees, the soil, the air all seem to be simmering, simmering with the energy of spring and the buckeye is the first to boil over into fruitfulness.

This deciduousness among evergreens is intrinsic to the buckeye magic. Their deciduous leaves are relatively expansive, thin, and short-lived, lacking the durability or waxy coatings of bay or live oak leaves that might keep in the more limited moisture during the long months of drought. Instead, the buckeye opts for another strategy, choosing a season of abundance and a season of fast rather than a life of continual frugality. In other words, buckeye leafing schedules often approximate a strategy of summer deciduousness. They leaf out earlier than average, often undoing the tender origami of their leaf buds in early February when the deciduous oaks, maples, and such may still be sleeping, and when willows and alders have perhaps put forth their flowers but find as yet more hindrance than reward in laying out their own leaves. Then, when opportunities for precipitation have passed and the peak energy need of flowering has subsided, buckeye leaves in sunny, exposed spots often begin to withdraw the chemicals of life in June or so. Shaded and cool individuals may keep their leaves functioning into August, but by then a large part of the buckeye population are rather sorry sights next to the oaks and others who built their leaves for the rigors of the season.

In contrast to many of our other deciduous trees, the buckeye’s strategy of early-leafing is linked with their strategy of insect, rather than wind pollination. Oaks, alders, willows, and hazel all produce their pollen in hanging catkins, strings of tiny flowers that may be thickly coated with golden pollen but have little or no petals to speak of. Rather than attracting insects with reservoirs of nectar signalled with colorful flowers, these trees rely primarily on a strategy of high pollen production, trusting that the random actions of the wind will blow some of that pollen to receptive female flowers on nearby trees. With such a strategy, a mass of leaves obscuring and blocking the pollen’s path to other flowers would be distinctly unhelpful, so most of these deciduous trees produce their flowers before leafing out. Buckeyes, in contrast, produce large candles of white flowers, which while apparently poisonous to some species, do contain nectar attractive to the right species of bees and other insects, which will travel from tree to tree, carrying along with them pollen on a more targeted course. These more substantial flowers open up well into spring, when the leaves have been up and working for some time and when the population of pollinating insects is higher.

The fruits of buckeyes are equally as distinctive as their leaves and flowers. Thick leathery pods first appear in summer and then can be retained on the tree for months, still clinging on to the leafless frames in fall. When one of these pods splits open, you can see the round seed peering out like the eye of a deer – hence the name. These pods are rich with tannins which are toxic to many creatures: Native Americans, the books say, used to drop the pods in water to stun fish, which would then float to the surface to be easily collected. But like acorns, these tannins could be leached out in running water, leaving the buckeyes an edible if not exactly choice food source. Other animals need no such culinary preparations and you may see squirrels chewing diligently away on buckeye pods, as they do on acorns.

Seed pods with fading leaves, August

After leafing out, flowering, fruiting, and shedding this year’s coat of nodding green feathers, the structural skeletons of buckeyes are laid bare to our view. In open areas, they may be round and spreading, the perfect image of symmetry, like an umbrella or cartoon mushroom, spreading a friendly circular cap above the earth. In crowded forest understories, they may stretch and spread, reaching their bony fingers out over creek beds to await the spring when their capillaries will fill once more with water and their quiescent buds will sense that the sun is once more on the rise. Ancient campaigners may thicken and calcify their central structures, turning the lissom limbs of young trees into continuous fortresses of wood, with embrasures here and there leading to cavities that shelter animals and windows that amuse humans. Though striking in dead profile, even these occasional Methuselahs will be softened and made young again when the leaves unfold, each tiny hand unclenching its fist, converting its store of contained force into a palm of bobbing welcome, springing open each little parasol to shade the big one, rounding out the surface to reveal a greater roundness, as our flesh makes human our bare bones, as our forests make a home from this rough rock in space.

Name: California Buckeye, Aesculus californicum

Buckeye refers to the seeds: large, round, brown, and somewhat shining like the eyes of a deer. I find this impression stronger when I see a half-opened pod on the ground, adding a resemblance to eyelids. Aesculus is an old Linnaean name, drawn from an older Roman name, apparently for a kind of acorn. Californicum is apt: this tree is endemic to (found only in) our state.