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Notholithocarpus densiflorus is often confused with:
Quercus chrysolepis
Plants that fill a similar niche:
Salvia rosmarinus Rosmarinus officinalis
Quercus nigra Quercus nigra
Quercus chrysolepis

Notholithocarpus densiflorus

Common Name(s):

Previously known as:

  • Lithocarpus densiflorus
  • Pasania densiflora
  • Quercus densiflora
  • Synaedrys densiflora
Phonetic Spelling
no-thoh-lith-o-KAR-pus des-i-FLO-rus
Description

 Tanoak is a medium-sized, broadleaf evergreen tree or shrub that measures 20 to 80 feet tall and up to 50 feet wide. It has a conical to a rounded shape with large horizontal branches. The Dwarf Tanoak is a shrub and is usually less than 10 feet tall. The leaves are thick, leathery, and light green. The flowers consist of male catkins that are erect, white, and then turn rust-colored. The female flowers are found at the base of the catkins. The flowers can be so dense that they hid the foliage. The fruit is an acorn that takes two years to mature. This tree is a member of the Fagaceae family which includes beeches, chestnuts, and oaks.

It is native to southwest Oregon and California. These trees are typically found along the Pacific Coast, in the Cascade Mountains and the Klamath Mountains, and down into southern California. It is the only member of this genus native to North America. All other members are native to southeast Asia and Indo-Malaysia.

The Tanoak was formerly in the genus known as Lithocarpus, but it now is a member of the genus Notholithocarpus. Lithocarpus originated from the Greek word, lithos, meaning "rock" and karpos, meaning "fruit."  Notho is Latin and means "false." This references the acorn fruits. The species name, densiflorus, means "densely flowered." It is commonly known as Tanoak or Tanbark-oak, but it is not a true oak even though it produces acorns. 

The Tanoak prefers full sun to partial shade. It performs best in rich, moist soils and mild temperatures. Once established, it is somewhat drought tolerant. It is hardy to USDA Zone 7.  It is wind pollinated and propagated by seeds and sprouts. 

The bark is reddish-brown, moderately thick, and has furrows and ridges. The leaves are simple, alternate, and persist for 3 to 4 years. Leaf fall occurs at the same time as acorn drop. The flowers look similar to those of a chestnut tree, and the fruits look similar to the acorns of an oak tree. 

The Tanoak tree provides shelter and food for mammals and birds and attracts butterflies and moths. The Tanoak bark was once a main commercial source of tannin. Northern California was once the main producer of high-quality leather. Once the tree was stripped of its bark, the tree was of little value.  It is now being devastated by a disease known as sudden oak death.

Seasons of Interest:

Bloom:  Spring and Summer                  Foliage: Year-round, leaf drop every 3 to 4 years            Fruits: Fall, matures every 2 years       Bark:  Year-round

Quick ID Hints:

  • broadleaf evergreen, moderate size conical or rounded shape
  • reddish-brown thick bark with furrows and ridges
  • stout, rounded, reddish-brown stems that are densely hairy when young
  • densely flowered in spring and summer with erect male catkin measuring 2 to 4 inches long, white, and then rust-colored
  • female flower is at the base of the catkin and is greenish-yellow
  • 1-inch long acorns that may be single or paired with shallow caps and dense bristles, take 2 years to mature

Insects, Diseases, and Other Plant Problems: Tanoaks are fairly resistant to insects, but oak worms may feed on the foliage. Up until the mid-1990s, this tree was mostly disease-free. However, this species has been become seriously affected by Sudden Oak Death. Spores are produced on the foliage that infects the trunk of the tree then resulting in the death of the tree. Unfortunately, this also results in the loss of habitat, shelter, and food for wildlife.

VIDEO created by Ryan Contreras for “Landscape Plant Materials I:  Deciduous Hardwoods and Conifers or Landscape Plant Materials II:  Spring Flowering Trees and Shrubs” a plant identification course offered by the Department of Horticulture at Oregon State University

 

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Cultivars / Varieties:
  • Notholithocarpus densiflorus var. densiflorus
    typical variety
  • Notholithocarpus densiflorus var. echinoides
    dwarf variety
Notholithocarpus densiflorus var. densiflorus, Notholithocarpus densiflorus var. echinoides
Tags:
#full sun tolerant#conical#drought tolerant#shrub#broadleaf evergreen#shelter#moist soil#food source wildlife#summer flowers#deer resistant#acorns#catkins#rounded#nesting sites#butterfly friendly#partial shade tolerant#full sun#tree#landscape plant sleuths course
 
Cultivars / Varieties:
  • Notholithocarpus densiflorus var. densiflorus
    typical variety
  • Notholithocarpus densiflorus var. echinoides
    dwarf variety
Notholithocarpus densiflorus var. densiflorus, Notholithocarpus densiflorus var. echinoides
Tags:
#full sun tolerant#conical#drought tolerant#shrub#broadleaf evergreen#shelter#moist soil#food source wildlife#summer flowers#deer resistant#acorns#catkins#rounded#nesting sites#butterfly friendly#partial shade tolerant#full sun#tree#landscape plant sleuths course
  • Attributes:
    Genus:
    Notholithocarpus
    Species:
    densiflorus
    Family:
    Fagaceae
    Uses (Ethnobotany):
    The wood is very hard and strong and is used commercially for lumber, fuel, or pulp. North American Indians used acorns as a food source to make soup, mush, or bread. The bark has an extract that was used to tan leather.
    Life Cycle:
    Woody
    Recommended Propagation Strategy:
    Seed
    Country Or Region Of Origin:
    Southern Oregon to California
    Distribution:
    California and Oregon
    Fire Risk Rating:
    high flammability
    Wildlife Value:
    Mule deer, squirrels, chipmunks, Stellar's jays, woodpeckers, and thrushes feed on the acorns. The tree also provides nesting and shelter for many mammals and birds. It attracts butterflies and moths.
    Play Value:
    Wildlife Cover/Habitat
    Wildlife Food Source
    Wildlife Larval Host
  • Whole Plant Traits:
    Plant Type:
    Shrub
    Tree
    Woody Plant Leaf Characteristics:
    Broadleaf Evergreen
    Habit/Form:
    Broad
    Conical
    Dense
    Rounded
    Growth Rate:
    Slow
    Maintenance:
    Low
    Texture:
    Medium
  • Cultural Conditions:
    Light:
    Full sun (6 or more hours of direct sunlight a day)
    Partial Shade (Direct sunlight only part of the day, 2-6 hours)
    Soil Texture:
    High Organic Matter
    Loam (Silt)
    Sand
    Shallow Rocky
    Soil Drainage:
    Good Drainage
    Moist
    USDA Plant Hardiness Zone:
    7b, 7a
  • Fruit:
    Display/Harvest Time:
    Fall
    Fruit Type:
    Nut
    Fruit Length:
    < 1 inch
    Fruit Width:
    < 1 inch
    Fruit Description:
    The fruit is a single or pair of oval-shaped acorns and requires two seasons to mature. Acorns begin to fall in mid-September to mid-November. The acorns are 1-inch long with shallow caps with dense bristles. The inside of the cap and the outer portion of the nut has dense hairs.
  • Flowers:
    Flower Color:
    Brown/Copper
    Gold/Yellow
    Green
    Red/Burgundy
    White
    Flower Inflorescence:
    Catkin
    Flower Bloom Time:
    Spring
    Summer
    Flower Description:
    The tree has male and female flowers. The male or pollen flowers are catkins that measure 2 to 4 inches long and appear as upright clusters. They are white but turn rust-colored. The male catkins have an unpleasant scent. The female or seed flowers are greenish-yellow. They are located at the base of the male catkin. Tanoak may flower from April to August, but the heaviest flowering occurs from June to August.
  • Leaves:
    Woody Plant Leaf Characteristics:
    Broadleaf Evergreen
    Leaf Color:
    Blue
    Green
    White
    Leaf Feel:
    Glossy
    Leathery
    Leaf Type:
    Simple
    Leaf Arrangement:
    Alternate
    Leaf Shape:
    Oblong
    Leaf Margin:
    Entire
    Serrate
    Hairs Present:
    Yes
    Leaf Length:
    3-6 inches
    Leaf Width:
    1-3 inches
    Leaf Description:
    The leaves are simple, oblong, alternate, and measure 3 to 5 inches long and 0.75 to 2.25 inches wide. Young leaves are densely hairy. Mature leaves are shiny, leathery, non-hairy, dark green on the upper surface and whitish-blue on the undersides. The margins may be entire or coarsely toothed.
  • Bark:
    Bark Color:
    Light Brown
    Red/Burgundy
    Surface/Attachment:
    Furrowed
    Ridges
    Bark Plate Shape:
    Round
    Square
    Bark Description:
    The bark on a mature tree is reddish-brown, 0.75 to 1.5 inches thick, and has narrow furrows. The flattened, rounded ridges sometimes become square plates.
  • Stem:
    Stem Color:
    Brown/Copper
    Red/Burgundy
    Stem Is Aromatic:
    No
    Stem Cross Section:
    Round
    Stem Surface:
    Hairy (pubescent)
    Stem Description:
    The stems are reddish-brown, stout, and rounded. One- to two-year-old stems are covered with dense rusty colored hairs.
  • Landscape:
    Landscape Theme:
    Butterfly Garden
    Attracts:
    Butterflies
    Moths
    Resistance To Challenges:
    Deer
    Drought