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Quercus garryana, commonly known as the Garry oak or Oregon white oak, is a deciduous tree or shrub belonging to the beech or Fagaceae taxonomic family (USDA 2018). It is native to the Pacific Coast of North America from Los Angeles County, CA at its southern extend and reaching up into British Columbia. It is more common to the west of the Cascade Range, but populations are scattered to the east as well (Gucker 2007). This species can be found in a variety of habitats--wetlands, mountains, valleys, grasslands, woodlands, and closed-canopy forests. Significant Oregon white oak habitat and populations have been lost primarily due to fire suppression, altered land use, habitat destruction, and introduced non-native species/invasive species. For example, numbers in the Willamette Valley are currently at about 15% of their pre-European abundance, and in some areas of Q.  garryana’s range, habitat loss may be as high as 95% (Gucker 2007).

There are three varieties of Q. garryana. The tree variety can grow to a height of 20-30 meters. The shrub varieties, Breweri and Semota, grow to be around 5 meters high. Differentiation of the shrubs can be deciphered by the velvety underside of Breweri leaves versus Semota’s more felt-like foliage (Flora of North America 2018). Oregon white oak has a deep taproot along with lateral roots (Gucker 2007). The branches commonly have multiple leaves growing out of a single node. The leaves are shiny dark green above and pale green below, with three or four rounded lobes per side. This angiosperm has small green flowers growing downward in catkins. The mature bark of the Oregon white oak is grayish brown and is furrowed in a checkered pattern.

Quercus garryana has monoecious flowers with 6 petals and sepals which are evenly spaced around the reproductive organs. They have 6-10 stamens and one pistil per flower, are wind pollinated, and produce an acorn when fertilized (Giblin 2018). Acorns are at an extremely high risk of desiccation and predation unless buried. Such burial is often facilitated by animals such as Douglas squirrels and Steller’s jays, with some of the caches inevitably being forgotten. This gives the acorn an increased chance of survival. Acorns readily germinate in warm moist weather with no need for a catalyst such as fire or cold (Gucker 2007).

Oregon white oak acorns are a major food source for many animals and insects living in the area, while the oaks themselves provide food, shelter, nesting material, and many other vital ecological services for a great many species, a number of which are at risk or endangered (Gucker 2007). Q. garryana’s ability to thrive in different soils and in rocky areas with different climates makes it an important feature in diverse ecosystems and a vital constant across environments.


Creative Commons Attribution 3.0 (CC BY 3.0)

© Emily LaRoche, Brandon McWilliams; Editor: Dr. Gordon Miller. Seattle University, EVST 2100: Natural History, Spring 2018.

Supplier: seattleu_natural_history

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