Mexican Blue Oak
Quercus oblongifolia
Family: Fagaceae
OTHER NAMES
Arizona blue oak, Sonoran blue oak
Spanish: encino azul, bellota, encino
CHARACTERISTICS
Deciduous tree, usually reaching 40-50’ tall but can reach 90’ often shorter in the low desert. Flowers in spring and acorns are ripe in fall. Nice fall color—often oranges or light reds. This is a good tree for tight spaces—the tree grows very fast and upright (unlike may of our native oaks and other trees that are wide and shrubby when they are young).
LANDSCAPE USE
A very upright-growing medium to large shade tree.
Photo by Bosque LaVida, iNaturalist
Quercus oblongifolia on SEINET
GROWING CONDITIONS
AN EXPLANAITION OF TERMS USED
SUN afternoon shade encouraged for young plants, older plants can take full sun, full to part sun in higher elevations
WATER moderate
SOIL prefers good drainage, amendments encouraged
HARDINESS hardy to about -20°F
BASIN middle zone
CONTAINER does ok in container but will not attain full size
NUTRITION moderate
MAINTENANCE very little
ECOLOGY
Flowers in spring with inconspicuous, wind-pollinated flowers. Acorns ripen in fall. Oaks are wildlife keystone species hosting a mind-boggling number of insects. This brings in a vast array of substrate-insectivorous birds (birds that spend their time on these trees eating the insects). The acorns are important food for many birds and mammals (and some species eaten by people). The trees also provide important habitat for many birds and mammals. Almost all the oaks host a multitude of moths and butterflies including the following species:
Mexican-M Hairstreak (Parrhasius moctezuma)
Arizona Sister (Adelpha eulalia)
Short-tailed Skipper (Zestusa dorus)
Arizona Dull Firetip (Apyrrothrix araxes ssp. arizonae)
Burgess’s Sleepy Duskywing (Erynnis brizo ssp. burgessi)
Clitus Duskywing (Erynnis juvenalis ssp. clitus)
Meridian duskywing (Erynnis meridianus ssp. meridianus)
Scudder's Duskywing (Erynnis scudderi)
Mournful Duskywing (Erynnis tristis)
Oaks also host a diversity of insects that cause growths called “galls”. Galls are protective nests for the larvae of various insects (mostly tiny stingless wasps) to develop protected from pests. The have a diversity of shapes from giant ball-like growths, to small growths, on leaves or young stems. These galls do not harm healthy trees. Emory oaks that grow in riparian zones and get really tall are a favorite nesting site for owls and other raptors.
Oaks attract numerous other insects which, in turn, attracts canopy-gleaning birds.
ETHNOBOTANY
Acorns can be used as food with some leaching of the tannins. The wood is used occasionally for various construction purposes.
NATURAL DISTRIBUTION
Found in the grasslands and in oak woodlands, often on gentle rolling slopes from 2,500-8,000’ across southeastern Arizona into New Mexico to Texas and south into Mexico.
TAXONOMY AND NAME
This plant is in the family Fagaceae, the beech family. There are 627 accepted species in the genus Quercus widely distributed in the northern hemisphere.
The genus "Quercus" is from Latin, meaning "oak", and “oblongifolia” refers to the oblong shape of the leaves.
The foliage has a blueish hue that attracts many oak lovers. Photo by Michael Woodruff, iNaturalist
Typical trunk of a Mexican blue oak, photo by Andrew Tree, iNaturalist
A ripe acorn, photo by Cricket Raspet, iNaturalist