Tuleyome Tales: Buckeyes, these chestnuts aren’t for roasting
- Mary K. Hanson
- Posted On
NORTHERN CALIFORNIA – You’ve probably seen them leafing out and blossoming all over the region, their newly formed leaves a bright chartreuse that will eventually turn darker green and take on a kind of fuzzy matt finish.
They’re trees that ignore the pre-set seasons so strictly adhered to by other trees: they wake up in the winter and settle down to sleep in the late summer.
They’re California Buckeyes (Aesculus californica), a species endemic to California – meaning that they grow here and nowhere else on earth.
The buckeye tree can grow up to 20 feet tall and have a branch-span of about 30 feet. When planted from seed it can sprout up 10 inches each year, and has the capacity to live for over 250 years. And it’s this tree’s seeds that are so spectacular.
Getting as a large as a fist, the dark chestnuts look like polished mahogany when they’re released from their leathery husks. The chestnuts drop to the ground in the wettest part of winter.
Each one sends out a long pinkish taproot that bores into the earth, and also releases a finely leafed sprout that forms above ground on a rose-colored stem. If it survives, this sprout will become the new tree.
Although they’re beautiful and fascinating, these are not the kind of chestnuts you can eat.
Sweet chestnuts are actually an entirely different species: Castanea sativa.
California Buckeye chestnuts contain a neurotoxic glucoside called “aesculin,” among other compounds, that can cause severe stomach pains, disorientation, muscle weakness and death in mammals, including humans.
Ingestion of the sprouts, leaves and seeds is also known to be linked to the spontaneous abortion of calves in grazing cattle.
Adult California ground squirrels, however, have a natural immunity to the toxins – just as they have a natural immunity to rattlesnake venom.
In the winter, you’ll often see the forest floor and areas around the squirrels’ burrows littered with chewed up, half-eaten Buckeye chestnuts.
Mule deer and Steller’s Jays have also been known to eat the leaves and chestnuts, but only in very small quantities.
Although not good as shade trees because they lose their leaves in the summer, California Buckeyes are great at binding the soil with their roots and are often used for erosion control. They can also thrive in drought stricken areas and in nutrient-poor soils where other trees fail.
In the spring, they display long 4- to 8-inch panicles of small, sweet-scented flowers (white or pink) which attract a wide variety of pollinators.
The blossoms are a favorite of the tiger swallowtail butterflies, and the trees are also the hosts to the caterpillars of the echo blue butterfly (Celastrina argiolus).
Care has to be taken not to plant the trees near apiaries, however, because the blossoms’ inviting nectar and pollen are poisonous to European honeybees.
Additionally, according to the USDA, “Human beings have been poisoned by eating honey made from California Buckeye.”
Of all of the flowers displayed on its panicles, only one will survive to actually develop into a chestnut. In the later summer months, you can see single chestnuts dangling here and there from branches of the trees like leathery bobs on pendulum strings.
As we mentioned before, the California Buckeye is one of the few trees in our state that “estivates” in summer.
All of its leaves shrivel and turn golden brown, and most fall off as the tree goes dormant. It’s this summer leaf-drop that can add fuel for wildfires in some of the trees’ natural range.
The chestnuts ripen in the fall, and then fall to the ground in the winter, starting the cycle from tree, to flower, to seed all over again.
Mary K. Hanson is a Certified California Naturalist, author, nature photographer and blogger (https://chubbywomanwalkabout.com/). She also teaches naturalist classes through Tuleyome, a501(c)(3) nonprofit conservation organization based in Woodland, Calif. For more information, visit www.tuleyome.org.