Blue Oak, Quercus douglasii

About Blue Oak (Quercus douglasii) 42 Nurseries Carry This Plant

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The Blue Oak is endemic to California and is found in foothills surrounding the Central Valley of California, the South Coast Range, North Coast Range and San Francisco Bay Area. It is also sometimes known as the Mountain Oak, and occasionally the Iron Oak. Blue Oaks are medium-sized deciduous trees growing up to 50-82 feet tall, usually with a somewhat irregularly-shaped crown, and a trunk 1.5-3 feet in diameter. The tallest recorded oak was found in southern Alameda County, at 94 feet. The bark is light gray with many medium-sized dark cracks; from a distance, it can appear almost white. The name Blue Oak derives from the dark blue-green tint of its leaves, which are deciduous, 1.5-4 inches long, and entire or shallowly lobed. The blue color can be subtle but becomes much more evident when viewed next to one of the live oaks with whom it shares its range, which tend to have much greener leaves. The acorns are around an inch long, often with a narrowed base, with a moderately sweet kernel, and mature in 6-7 months from pollination.

Blue Oaks are beautiful but very slow growing trees. They usually only add a few inches per year. Plant on dry, well drained slopes. They prefer full sun but will tolerate part shade, especially when young. They can handle occasional summer water (1x per month).

Plant Description

Plant Type

Tree

Size

16 - 82 ft tall
30 ft wide

Form

Upright, Rounded, Upright Columnar

Growth Rate

Slow

Dormancy

Summer Semi-Deciduous, Winter Deciduous

Fragrance

None

Flower Color

Yellow, Cream, Green

Flowering Season

Spring, Winter

Wildlife Supported

A very large variety of wildlife are attracted to oaks. Many insects are attracted to Oaks generally, including the following butterflies which use Oaks as host plant: California Sister, Propertius Duskywing, Mournful Duskywing, Golden Hairstreak, and Gold-Hunter's Hairstreak.
Bird gardens

Butterflies & moths hosted ( 11 confirmed

, 160 likely * ) SHOW ALL

Mournful Duskywing Erynnis tristisErynnis tristis

Gold Hunter's Hairstreak Satyrium auretorumSatyrium auretorum

Fruit-Tree Leafroller Moth Archips argyrospilaArchips argyrospila

Pacific Tent Caterpillar Malacosoma constrictaMalacosoma constricta

Feralia februalisFeralia februalis

Dyseriocrania auricyaneaDyseriocrania auricyanea

Decodes fragarianaDecodes fragariana

Landscaping Information

Sun

Full Sun, Part Shade

Moisture

Low

Summer Irrigation

Max 1x / month once established

Nurseries

Carried by 42

Ease of Care

Very Easy

Cold Tolerance

Tolerates cold to 0° F

Soil Drainage

Fast

Soil Description

Tolerant of a variety of soils as long as adequate drainage is provided. Soil PH: 6.0 - 8.0

Common uses

Bank Stabilization, Deer Resistant, Bird Gardens, Butterfly Gardens

Companion Plants

coffeeberry (Rhamnus species), Buckbrush (Ceanothus cuneatus), Chaparral Whitethorn (Ceanothus leucodermis), Big Berry Manzanita (Arctostaphylos glauca), Buckeye (Aesculus californica), Mountain Mahogany (Cercocarpus betuloides), other oaks (Quercus species), pines (Pinus species), and native grasses.

Maintenance

Young trees should be pruned for desired shape

Propagation?

From acorns, although hybridization is common. For propagating by seed: Fresh seeds sow in fall outdoors or stratify to hold for spring sowing. If started indoors or in glasshouse, stratify first for 1.5 mos. (USDA Forest Service 1974).

Sunset Zones?

1, 2, 3, 4, 5, 6, 7*, 8, 9*, 10, 11, 14*, 15*, 16*, 17, 18*, 19*, 20*, 21*, 22, 23, 24

Natural Setting

Site Type

Rocky, hot, dry hillsides and slopes usually below 3,500 ft. in the Coast Ranges and foothills of the Sierras, often in large stands of Blue Oak Woodland or Blue Oak Savannah

Climate

Annual Precipitation: 7.8" - 71.1", Summer Precipitation: 0.14" - 2.08", Coldest Month: 24.6" - 56.2", Hottest Month: 45.5" - 80.0", Humidity: 0.53" - 27.98", Elevation: 6" - 11310"

Alternative Names

Common Names: Iron Oak, Mountain Oak

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Sources include: Wikipedia. All text shown in the "About" section of these pages is available under the Creative Commons Attribution-ShareAlike License. Plant observation data provided by the participants of the California Consortia of Herbaria, Sunset information provided by Jepson Flora Project. Propogation from seed information provided by the Santa Barbara Botanical Garden from "Seed Propagation of Native California Plants" by Dara E. Emery. Sources of plant photos include CalPhotos, Wikimedia Commons, and independent plant photographers who have agreed to share their images with Calscape. Other general sources of information include Calflora, CNPS Manual of Vegetation Online, Jepson Flora Project, Las Pilitas, Theodore Payne, Tree of Life, The Xerces Society, and information provided by CNPS volunteer editors, with special thanks to Don Rideout. Climate data used in creation of plant range maps is from PRISM Climate Group, Oregon State University, using 30 year (1981-2010) annual "normals" at an 800 meter spatial resolution.

Links: Jepson eFlora Taxon Page CalPhotos Wikipedia Calflora

Blue Oak

Quercus douglasii

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Blue OakQuercus douglasii

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Blue Oak

Quercus douglasii