Chrysolepis Chrysophylla, giant golden chinquapin, with hairstreak butterfly, an insect whose larvae feed on this species.  Drawing: Erther Gruber  McEvoy

     The new treatment of Fagaceae in volume 3 of the Flora of  North America (1997) by Kevin C. Nixon, Paul S. Manos, Richard J. Jensen and Cornelius H. Muller has excellent distribution maps, leaf and fruit drawings and keys.  My treatment of the Fagaceae for the Oregon Vascular Plant Checklist is based on theirs.  Oregon has two species of Chrysolepis (formerly Castanopsis), one species of Lithocarpus (with two varieties), and six species of Quercus, including one hybrid.  The cupule or involucre is the most important diagnostic feature of the Fagaceae.  The cupule is the cap of the acorn in Lithocarpus and Quercus and the spiny bur that surrounds the fruits in Chrysolepis. In Oregon, the southwestern region of our state contains the greatest diversity of taxa in this family.  All three genera have evolved  shrubby or small  tree forms in these hotter, drier habitats.

     Field botanists, naturalists and foresters are always unhappy with a change in a well-known genus name, but the switch from Castanopsis to Chrysolepis occurred in a 1948 monographic study.  H. Hjelmquist, a Swedish taxonomist, chose to separate the Western United States chinquapin taxa (two temperate species) from the true Castanopsis of Asia  (120 tropical and subtropical species) on the basis of cupule structure.  Hjelmquist chose the name Chrysolepis which means “gold scale” referring to yellow glands on various plant structures.

     The chinquapins are distinct from other Oregon Fagaceae in their fruit structure, with a densely spiny involucre that completely encloses one to several angular or round nuts. The lower surface of  the leaves has a dense layer of rusty-golden, glandular pubescence which is visible from some  distance.  Chrysolepis chrysophylla  var. chrysophylla (golden chinquapin) grows from sea level to 2,000 meters along the coast from Washington to northern California, extending inland to the Cascades and Sierra Nevada.  These trees, up to 45 meters in height, typically have flat leaves.  Chrysolepis chrysophylla var. minor  comprises shrubs which range from 2-5 meters tall; their leaves are strongly folded along the midvein.  The shrubs grow on rocky, open slopes, in conifer forests and chaparral communities from 300-1800 m in California and southern Oregon.

     Chrysolepis sempervirens (bush chinquapin) is a low rhizomatous shrub (up to 2.5 m tall) which occurs mostly at higher elevations in California and southern Oregon.   Its low growth form and blunt-tipped leaves separate it from C. chrysolepis var. minor.

     Lithocarpus densiflorus (tanoak) has a single species in western North America while the Indomalaysian region has approximately 300 species.  The genus is present in the fossil record of western North America.  The cupule or cap, which covers the basal portion of the single large nut, has strongly reflexed scales that are hooked at the tip.  There are two varieties in California and southern Oregon. Lithocarpus densiflorus var. densiflorus is a tree ranging from 20-45 meters tall.  It occurs in mixed evergreen and Coast redwood forests from 0-1500 m.  The leathery evergreen leaves are entire or slightly serrate and are up to 12 cm long.  They are convex toward the tree axis (adaxially), a feature that is often difficult to see on herbarium specimens.  Lithocarpus densiflorus var. echinoides is a shrub up to 3 m but generally less than 2 m.  The leaves are much smaller (up to 6 cm) than the typical variety, and the blades are flat.  These shrubs grow in the Siskiyou region of southern Oregon and in the Sierra Nevada south to Mariposa County, California.

     (Editor’s note:  Part II of Henrietta Chambers’ taxonomic notes on Oregon Fagaceae will appear in the next Oregon Flora Newsletter.)