My favorite way of enjoying nature is to watch small changes unfold over the seasons, to visit the same tree, for example, throughout the year, and see the passing of time written in the branches. Our native California buckeyes (Aesculus californica) are a feast for the eyes in every season and one of my favorites to visit in this way.

California buckeyes have a graceful appearance with elegant silver-gray bark and branches that meander gently as they lengthen. Growing in both shrub and tree forms, between 15 and 40 feet, they typically have multi-trunked structures, and rounded crowns that grow as wide as they do tall, giving them a pleasing symmetry.

Aesculus californica are endemic to California and southern Oregon, meaning that they are not found growing naturally anywhere else. Paleobotanists (scientists who study the evolutionary history of plants) consider them a paleoendemic species, indicating they were once much more widespread, their range restricted over time to a smaller, more specialized geographic area.

Today, California buckeyes grow along the central coast ranges, in the foothills of the Sierra Nevada and Cascade ranges, and in woodlands throughout the Central Valley. They can be found on dry slopes, in canyons, and along stream edges, providing natural erosion control, and have been known to live up to 300 years.

These gorgeous trees are a beautiful example of the resilience of California native plants to the challenges of our Mediterranean climate, with hot dry summers and mild wet winters. These adaptations are part of what makes this tree so dynamic and compelling to observe. In mid to late winter Aesculus californica is one of the first trees of the year to put out new foliage, their soft chartreuse buds bursting with new growth as early as February. This early start helps them to take advantage of the winter rains while avoiding the heat of late summer.

By March and April, their branches will be flush with shiny dark green, palmately compound leaves up to 7 inches around. Each leaf has five to seven oblong-lanceolate leaflets, with finely serrated edges radiating from a single point, like fingers on a hand.

The leaves alone are beautiful, but California buckeyes really begin showing off in May and June with their stunning floral displays. In full bloom, the tree looks like a giant bouquet. The flowers form in panicles, conelike clusters between six to 12 inches in length, made up of many pink and cream blooms, with four delicate petals and long stamens carrying bright orange pollen.

Abundant blooms provide nectar to hummingbirds, butterflies, moths, and many species of native bees which in return provide the service of pollination. Most commonly one or two buckeyes will develop per flower cluster, each resembling a small green pear.

California buckeye trees have developed several clever ways to protect themselves and ensure reproductive success. One of those strategies is that all parts of the tree are poisonous to humans and other mammals. Toxicity increases the chances of their seeds being left to sprout rather than being eaten in large numbers and ensures that their leaves will not be overgrazed. Tender early leaf growth has lower levels of toxicity and is sometimes grazed upon by deer and California ground squirrels are the only mammal adapted to the toxicity of raw buckeye seeds.

These protective toxins are also present in the nectar and pollen of the tree. Native bees have coevolved with the trees in our region and are able to tolerate the toxins, whereas European honeybees, brought to North America by European settlers in the early 1620s, are not adapted to these toxins and can be harmed if they consume the nectar in large quantities.

Beekeepers have found ways of mitigating the risks to European honeybees by planting other plants with similar bloom times nearby, allowing for a wider range of nectar sources thereby reducing the risk of overconsumption by a hive, or by moving hives during the buckeye flowering period.

While European honeybees are the most recognizable bee to most of us, California is home to over 1600 species of native bees, many of whom depend on California buckeye blooms for nectar. California native bees range in size from the Perdita minima (currently known to be the smallest bee in the world!) measuring just under two millimeters, to our largest species, the Valley Carpenter Bee or Xylocopa varipuncta that grow up to an inch in length. Visiting a California buckeye in bloom is a fantastic opportunity for curious naturalists and hikers to get to know some of our native pollinators.

California buckeyes are a culturally significant plant for many indigenous Californians. Various parts of the buckeye tree were used for medicine, and fire drilling. Buckeye seeds were used for fishing, by mashing the seeds and pouring them into water, which dazed or killed fish, making them easier to catch.

Many indigenous Californian peoples including Costanoan, Salinan, Kitanemuk, Serrano, Wappo, Sierra Miwok, Coast Miwok, Chumash, Kawaiisu, and Northern Maidu used buckeye seeds for food in times of scarcity, while the Pomo used them even when other food sources were plentiful. Raw buckeyes are poisonous, but after an extensive process of grinding, boiling and leaching the toxic tannins, a meal could be formed for use in cooking, similar to the process of leaching toxins from acorns.

Most deciduous trees hold onto their leaves until October or November, but California buckeyes are summer deciduous, dropping their leaves in July and August when temperatures are high and water is scarce. Going dormant in midsummer, the tree conserves water and is more resistant to drought, another clever adaptation to our intense summers.

Leaves gone, the pear-shaped buckeyes are left hanging like ornaments on the branches. As summer turns to fall, the husks dry, split open, and the glossy brown-orange buckeye is revealed giving a sense of the tree’s namesake, the eye of a deer.

In October and November, buckeye seeds begin falling to the ground, leaving the branches ever more graceful in their simplicity. The tree will remain dormant until February comes and starts the process anew and last year’s fallen buckeyes will begin sending down their tap roots shortly after the first rain.

The best way to plant a buckeye is to grow one from a freshly fallen seed, as they dry out quickly. Plant them directly in the ground rather than in a pot which can inhibit the tap root and stunt the tree long term. Once established they are drought tolerant, easy to maintain and provide dynamic nature watching and beauty throughout the year.