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What is a Garry Oak?

Garry Oak (Quercus garryana) trees are the only oak trees native to British Columbia. They are known by many other names such as White oak and Oregon oak, Pacific Post oak, Western White oak, Brewer oak, and Shin oak. They are members of the Family Fagaceae, the Beech family.


Garry Oaks are a broad leaved deciduous hardwood.

Bark is light grey with many splits and ridges, smooth on young stems, breaking into shallow fissures and long, broad grey or grayish-brown, scaly ridges on older trunks.
Leaves are alternate, simple, and thick with 5-7 deeply cut rounded lobes, they are 9-18cm (3-6 inches) long, dark green, shiny and smooth above, pale green or orange brown, smooth or hairy below.
Wood is hard, strong, heavy, ring porous, light yellowish brown with almost white sapwood.


On average, under favorable conditions, mature Garry Oak trees may grow to 15-27m (50-90feet) tall and 60-100cm (24-40 inches) dbh (diameter at breast height). Garry oaks generally grow slowly in both height and diameter and take about 25 years to mature and can live for upwards of 400 years. Garry oaks have a short stout trunk that is rarely unbranched for more than 3-5m (10- 15 feet), the tree crown is broad and round topped, consisting of many thick gnarled twisting branches. Growing season is, on average, from April to September.

Rooting Habit

Garry Oaks have a high percentage of lateral roots in the upper soil layers as well as a deep taproot which makes them very wind-firm even in wet areas.

Reaction to competition
Garry Oaks have been classed as having intermediate to very low tolerance of shade depending on the situation. Mature Garry Oaks are generally not tolerant of over-topping by Douglas fir and other conifers and in these situations the Garry Oaks may die. Seedlings, however, appear more shade tolerant as they will grow in the shade of mature Garry Oaks and other trees.




Garry oak trees have both male (catkins) and female flowers on the same tree. The slim staminate flowers (catkins) are pale yellow tinged with green. The closed pistillate (female) flowers are small, deep red, and covered with whitish hairs, the interior of these flowers is green-yellowish, and they may be single or as many as 5-6 together. Flowers appear with new leaves and extension of twig growth.  Flowering is at the fullest when the leaves are approximately half size. The flowers are fertilized in the spring from March to June depending on elevation and latitude. When the leaves approach full size the catkins are withered and on individual trees flowering lasts only about a week. Flowering may be abundant but it is variable between and within stands and locations.



These seeds/fruits mature in one season and fall from the tree in late August to November. Garry Oak acorns are not dormant, they begin to grow right away, producing a long tap root in the fall, but no shoots or leaves are produced until the following spring. Acorns must be kept moist until they germinate (greater than 30% moisture), viability has been greater than 75% in the few samples tested, normally seeds retain viability only until the next growing season.

The mature acorn is smooth and brown, 1.5 to 3 cm (0.5 to 1.25 inch) long, weighing an average of approximately 5g. The acorns are sweet and edible and enclosed for ~1/3 length by a shallow cup of thickened hairy scales at the base. One mature Garry Oak tree can produce thousands of acorns, but acorn production varies by year for each tree, and in some years, a mature tree may produce no acorns at all.

Vegetative reproduction
Garry oak sprouts abundantly from dormant buds on cut stumps, root collars and along exposed trunks, spread of Garry oak by root sprouts has been noted.