The oak is a long lived tree, often exceeding 500 years. With a trunk and limbs that are thick and sturdy, it’s rarely damaged by storms—the leaves are marcescent in the north, not dropping until spring, and hold snow loads of impressive weights! Wind shears have been known to strip the tree bare, leaving the branches intact. About the only feat of nature to regularly damage an oak is lightning—of all the tree species struck by lightening, the oak is most frequently hit.
Because of its endurance this tree came to symbolize the profound and unyielding strength and steadfastness of Christians’ faith in the face of adversity. St. Sebastian is depicted as being lashed to an oak.
(San Sebastian, El Greco, image public domain)
With its nearly incorruptible wood it came to connote salvation, and is symbolic of physical and moral vigor. And this explains its association to the Virgin Mary.
According to legend, the Christianization of heathen druidic tribes in Germany by Saint Boniface was marked by his felling of an oak, where upon a fir tree immediately grew and whose triangular shape symbolizes the Trinity—more on the fir in another column.
In the Bible, Abram moved his tent and came and dwelt by the oaks of Mamre, which are in Hebron, and there he built an altar to the LORD (Gen 13:18). Later we read that Joshua erects a large stone under an oak tree as the first covenant of the Lord (Josh. 24:26). In Isaiah 61, the prophet refers to the Israelites as “Oaks of Righteousness”.
And now you know that an image of a saint with an oak alludes to the saint’s firm incorruptible faith.
(St. Paul the Hermit fed by the Raven, II Guercino, image public domain.)