Quercus

( KWER - kuss )

At-A-Glance Information

This genus is commonly known as Oak, and has a native range that is widely distributed across the Northern Hemisphere. Foliage is typically varying shades of green, and can be lobed or have spines. There are both deciduous and evergreen species in this genus, and they serve as keystone species in many different environments around the world. These slow-growing landscape trees produce both male and female flowers in the same individual, and acorns that take between 6 and 18 months to mature. Use oaks as landscaping trees in large gardens, or as shade trees. Take care when planting Oak trees in the landscape, as they are toxic to humans, pets and livestock if ingested.

Quercus Species and Varietals

The genus Quercus is a member of the plant family Fagaceae and includes 500 species. The genus name is derived from the Latin word kwerkwu, meaning 'oak'. The best growing zones for these classic landscape trees vary depending on the species grown. For more information, see the descriptions below. To find your zone, click here: Zone Map.

Quercus alba (White Oak)
This species is native to eastern and central North America, and typically reaches about 80-100 feet tall when mature. Canopies can become quite massive. At higher altitudes, these plants tend to grow as large shrubs. Bark is ash-grey (very uncommonly white) and it peels somewhat. These trees can live for 200-300 years.

Quercus aliena (Galcham Oak, Oriental White Oak)
This species reaches 100 feet tall and has fissured greyish-brown bark. Leaves are hairy and grey-white on undersides. The wood is used in this tree's native range (Korea, Japan, China and Taiwan) for building boats and as flooring for houses. These trees can grow in partial shade to full sun, form deep taproots, and tolerates strong winds but not soggy soils.

​Quercus arizonica (Arizona White  Oak)
This species is native to Arizona, New Mexico, Texas, and Mexico in the states of Sonora, Chihuahua, Coahuila, Sinaloa, and Durango. This is one of the largest southwestern Oaks and can reach up to 60 feet tall.

​Quercus austrina (Bastard White Oak, Bluff Oak)
This species of Oak is endemic to the southeastern United States and can reach between 45 and 60 feet tall when mature. Leaves are narrow, and these trees are tolerant to clay, sand, loam, acidic, and well-draining soils. It also has a high drought tolerance.

Quercus x bebbiana (Bebb's Oak)
This species is a naturally occurring species of Oak that is a cross between White Oak (Quercus alba) and Burr Oak (Quercus macrocarpa). These trees reach up to 50 feet tall when mature, and the acorns they produce are sweet enough to be palatable to humans.

​Quercus berberidifolia (California Scrub Oak, Scrub Oak)
These trees form small evergreen to semi-evergreen shrubs and is native to California. They commonly reach between 3.5 and 6.5 feet tall (exceptionally to 13 feet). The specific epithet refers to the leaves of this species, which are similar in look to those on Barberry (Berberis) shrubs.

​Quercus bicolor (Swamp White Oak)
These trees are native to North America, where it grows rapidly to between 60 and 80 feet tall. Foliage is green, and the bark is greyish-brown. It is an important species in lumber production, and is also widely grown as an ornamental tree.

​Quercus x bimundorum (Two Worlds Oak)
This species is a cross between Quercus alba and Quercus robur. They typically reach about 40 feet tall. Varieties include 'Crimson Spire' (also called 'Crimschmidt'; pictured, with a columnar growth form), 'Midwest' (also called 'Prairie Stature', with a pyramidal growth form) is a popularly grown cultivar.

Quercus boyntonii (Boynton Sand Post Oak, Boynton Oak)
This species is considered rare, and forms a shrub or small tree. They reach a maximum of 20 feet tall and produce green leaves with large lobes. Currently, these trees are only found in Alabama, though historically this tree has been seen in Texas, as well. The species is considered critically endangered.

Quercus canariensis (Algerian Oak, Mirbeck's Oak, Zean Oak)
These Oaks are native to Portugal, Spain, Tunisia, Algeria, and Morocco. They are named for the Canary Islands, which they were once seen growing on, though they have since been eradicated. These are medium-sized deciduous to semi-evergreen trees that reach between 66 and 98 feet tall when mature. 

Quercus chihuahuaensis (Chihuahua Oak)
These Oaks are native to Texas and northern Mexico, and reaches about 33 feet tall. Leaves are entire to toothed and are green on top and yellowish-grey underneath. 

Quercus dentata (Japanese Emperor Oak, Daimyo Oak, Sweet Oak)
These deciduous trees are native to Japan, Korea, and China and produce flowers in May, with acorns maturing from September to October. Trees reach between 66 and 82 feet tall at maturity, and have larger leaves than most other species in the genus. 

Quercus depressipes (Depressed Oak, Davis Mountain Oak)
This species of live oak forms a shrubby evergreen bush that reaches just 40 inches tall. These plants are found on grassy slopes along mountain ranges and are native to Mexico and the United States.

Quercus douglasii (Blue Oak, Mountain Oak, Iron Oak)
Endemic to California, this species is the state's most drought-tolerant deciduous oak. These medium-sized trees have sparse foliage, and typically are single-trunked but can have multiple trunks, as well. Trees grow slowly, about a foot per year, and bark is light gray. Foliage is bluish-green and pollen is severely allergenic.

Quercus durata (Leather Oak)
Endemic to California, this species of Oak produces leathery leaves, and forms a low-spreading shrub with rigid branches and deep green foliage. Great for hillside plantings in need of erosion control.

Quercus fabrei (Faber's Oak)
This species of Oak is deciduous, and is native to southern China. They can take the form of a large shrub or a tree that reaches up to 65 feet tall. Elongated leaves are serrated with small teeth, and are wider at the tip than the base.

Quercus frainetto (Hungarian Oak)
These deciduous trees can reach up to 125 feet tall and 66 feet wide, with a trunk girth of almost 7 feet. Bark is light grey and twigs are typically stout. Foliage is green and leaves are quite large (between 6-10 inches long). These are cultivated in larger parks and gardens due to their size, and the cultivar 'Hungarian Crown' is a choice variety with a handsome canopy.

Quercus gambelii (Gambel Oak, Scrub Oak, Oak Brush, White Oak)
This species is named for American naturalist William Gambel, and reach an average of 10-30 feet tall (exceptionally up to 60 feet). Branches are irregular and crooked, flexible enough to bend without breaking under heavy snow. Leaves are glossy and dark green, with pale velvety undersides. After fire, these Oaks quickly re-establish from root sprouts. Drought-tolerant.

Quercus garryana (Garry Oak, Oregon White Oak, Oregon Oak)
This species of Oak trees is native from California north through British Colombia. It is named for Nicholas Garry, the deputy governor of the Hudson's Bay Company. These plants can grow as trees or large shrubs, and can grow to reach 500 years old. Average tree height is about 80 feet tall (10-15 feet tall for shrubs), foliage is green and glossy,

Quercus germana (Mexican Royal Oak)
This species is native to mountainous cloud forests in eastern Mexico, and produces a small to medium-sized tree reaching up to 40 feet tall when mature. It is a type of white oak, and produces green foliage with entire margins (not lobed or toothed).

Caring for and pruning Quercus Trees

Oaks in the Black Oak Group, (Coast, interior, and Canyon Live Oaks, Shreve Oak and Kellogg’s Black Oak) are best pruned in the warmer, drier portion of the year: after the end of spring rains and before the fall rains begin. Roughly, late May/early June to mid-to- late-October is best. This is to avoid helping the pathogen, Sudden Oak Death, Phytophthora ramora –which seems to infect best in cool wet weather. If you have California Bays close to the above mentioned oaks, you might consider removing the California Bay touching the oak canopies or removing all branches that touch or shade any part of the oak canopies since the wet leaves of the Bays are excellent incubators for the active propagules of one of the reproductive stages of this aggressive organism.

Propagation

Problems and Pests

Gallery

Camellias are great candidates to be grown as container plants on your patio.
A field of thea sinensis
Camellia hiemalis 'Shishi Gashira'

Videos

How to identify Willow Oak Trees.
Propagating camellias

Resources

Wikipedia: Oak
The New Sunset Western Garden Book: The Ultimate Gardening Guide (2012) - Pages 544 - 550, Quercus
If you have any questions, comments, concerns, or photos you’d like to add to the gallery, please let me know by sending me a message using the button below!
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