Quercus (Oak) Notes

Campus oaks

More than the redwood on its seal, Stanford’s tree scene is defined by its native oaks, dominated by coast live oak, the most numerous tree on campus and the one that sets the deep, rich green against which every other green is compared. Valley and blue oak follow in abundance, the latter especially common in the foothills, though indigenous giants also stand on central campus – one before Dinkelspiel Auditorium – and in the Arboretum as well.

Oaks are famously variable within a species, and they also hybridize, almost always within their own section (see below). At oak society meetings, experts exchange knowing smiles as neophytes earnestly search for reliable ways to distinguish similar species. Jolon oak, the named hybrid between valley and blue oak, is undercounted and hence understudied in the region; inventories rarely identify it explicitly. Oak classification resists easy resolution: at Jasper Ridge, Shreve oak and relictual Palmer oak were each once thought to be other species, though for different reasons – see their entries. Shrub oak species and California black oak also grow at Jasper Ridge, though not the majestic goldcup oak, which becomes common in the mountains just beyond.

History

Frederick Law Olmsted specified the propagation of vast numbers of coast live and interior live oaks for Stanford’s grounds. They are “live” oaks because they’re evergreen: our mild climate and plentiful winter sun allow them to produce food year-round. He made no mention of the deciduous valley oak or blue oak. Gardener Thomas Douglas did collect and sow local acorns of valley and coast live oak, and also propagated California black and goldcup oak – yet his work diaries likewise never mention blue oak, despite grand specimens then (and still) standing in the Arboretum, only steps from his nursery.

Leland Stanford wished, as far as possible, that no mature oak be sacrificed to campus development. He also directed that the first dormitories be named for the Spanish monikers of the coast live oak and valley oak. In a telegram to David Starr Jordan dated May 16, 1891, he wrote:

I approve the proof sheets of your prospectus but have decided to name the dormitories after live oak and white oak which are the principal natural trees of this valley. For the boys dormitory Encina Hall and for the girls dormitory Robles Blancho [sic] Hall, being the Spanish names for the live oak and the white oak.

Tenants and afflictions

Native oaks are central to local biodiversity, hosting a plethora of minute organisms fundamental to the food web, their benefit amplified by the sheer prevalence and size of these trees. Noting which creatures participate in the complex ecology of oaks – or any plant – sharpens our sense of their ecological value, though what constitutes habitat for one organism may be an affliction for another.

California oak moth and tussock moth caterpillars devour coast live oak leaves; in outbreak years such as spring of 2026, the larvae can often be spotted descending on silk threads and entire trees may be defoliated – an alarming sight, though healthy trees usually recover. Parasitoid wasps and other insects, rather than birds, are the principal natural enemies of these caterpillars.

Native oak root or honey fungus (Armillaria mellea and kin) occurs naturally in the roots of coast live oak and many other oaks, fruiting as honey-colored edible mushrooms at the trunk base. Problems are exacerbated by horticultural practices such as summer irrigation near the root crown – all but unavoidable in lawn settings, though keeping turf and watering well away from trunks helps.

Sudden oak death, caused by the fungus-like organism Phytophthora ramorum, has killed millions of tanoaks and many oaks along the California–Oregon coast since the mid-1990s. Coast live oak and California black oak are the most susceptible; other natives such as redwood, toyon, madrone, and bay laurel usually show only foliar or twig infections, though bay laurel, in particular, can pass the pathogen on to adjacent oaks and tanoaks. Jasper Ridge has been monitoring for the disease, and so far our oaks have been spared.

Gall-spotting is an underappreciated pastime: scan oak leaves for an array of sometimes colorful growths of fantastical shape, with pleasingly apt names: striped volcano, spined turban, red cone, pink bowtie. These form from plant tissue in response to tiny wasps laying their eggs within; the resulting structures shelter the developing larvae. Other invading organisms such as fungi and bacteria can induce galls as well.

Mistletoes are hemiparasitic plants that usually photosynthesize but tap the host tree’s water and nutrients, typically without much damage. Clumps are sometimes seen on our deciduous oaks such as valley, as well as on scarlet and water oak. About a dozen large clumps were carefully removed from the sizeable water oak near Bing Concert Hall in 2024.

Burls – large, knobby swellings on trunks or branches – arise from proliferating, often dormant, bud tissue, typically in response to stress or fungal and other infection; their intricate grain is sometimes prized. A coast live oak between Kingscote Gardens’ east entrance and the Humanities Center bears an immense, rounded burl bulging on either side of the trunk. Peruvian pepper tree trunks are often heavily burled as well.

Acorns

For most native Californians, acorns were a daily staple. Among the local Puichon, nuts of valley, black, and coast live oak were ground and then leached in water to remove the bitter tannins; a large rock with food-grinding holes on top can be seen at Jasper Ridge.

Other preparations were known. Among the Shasta, acorns were buried in swampy ground for a year, then roasted and eaten whole; another method let shelled acorns mold in a basket before burial in clean river sand until they blackened and were deemed ready. Across cultures, from California to the Mediterranean, acorns have long been prepared in various ways and are still valued in regional traditions – most famously as seasonal feed for pigs in the oak woodlands of Spain and Portugal.

Oak planting at Stanford

David Schrom, founder of the local group Magic, observed in the 1970s that few younger native oaks were in evidence and that most mature trees appeared to be of similar age. In response, Magic has led extensive plantings at Stanford since the 1980s, in collaboration with campus grounds management – a decades-long experiment in establishing native oaks. Student volunteers sow acorns in the Dish, protect them with tubes against deer and rodents, and return to water them until the seedlings are established. Often two species are sown in the same hole to compare vigor; the weaker is not always culled, leaving curious twin-stemmed pairings in the field. By 2000, more than 2,000 trees had been established, mostly by direct seeding.

On campus proper, between 2004 and 2013 Magic trialed various non-local oaks at several peripheral sites, for example near Palo Road opposite Hoover Pavilion and along Galvez Street near El Camino Real. The group planted five-year-old seedlings raised from acorns, many collected from the Shields Oak Grove, the renowned quercetum at U.C. Davis. Because the grove contains many oak species, wind pollination makes the parentage of individual acorns uncertain; unsurprisingly, many of the resulting seedlings proved to be hybrids. Engelmann oak has been a notable success and is now planted in choice campus locations; Canby oak is increasingly seen as well.

Our native California black oak has met with only moderate success on campus; the grove in Lathrop Park is the best-established. Shreve oak, goldcup oak, the shrub oaks, and tanoak have seen little experimentation in recent decades. Blue oak’s story is told in its own entry.

A four-year survey of native oaks in Palo Alto, completed in 2002, estimated about 13,000 trees: coast live oak accounted for 84%, valley oak 15%, and blue oak and black oak together for less than 1%. A volunteer mapping effort begun in 2017, based on citizen observations, currently shows coast live oak at 78%, valley oak at 19%, and blue and black oak each at about 2%.

The oaks native to California are QQ. agrifolia, chrysolepis, douglasii, durata, engelmannii, garryana, kelloggii, lobata, palmeri, parvula, sadleriana, tomentella, and wislizeni, as well as several hybrid and shrub oak species; nine or so are described here.

In addition, Stanford has several U.S. oaks from outside California, chief among them QQ. coccinea, macrocarpa, palustris, rubra, and virginiana. Campus oaks from other countries include QQ. cerris, ilex, robur, and suber.

Oak classification

Quercus subgenus Quercus

New World, high-latitude clade. Mainly in Americas, some Eurasia & north Africa.

Quercus subgenus Cerris

Old World, mid-latitude clade. Mainly in Eurasia, some N Africa.

Name derivation: Quercus – classical Latin name for oak.