Oak - a symbol of strength and longevity

Having tidied up my little tree nursery last weekend in preparation for the guerrilla planting season ahead, I thought I would write about the mighty Oak and help you differentiate between the two predominant species of Oak in Ireland - the Sessile Oak, and the Pedunculate Oak.

Oaks are large, deciduous trees that grow up to 20–40m tall and belong to the Beech family of plants - Fagaceae. There are 500 species of Oaks around the world. The Oaks most found in Ireland are the Sessile Oak (Quercus petraea) also known as the Irish Oak, and the Pedunculate Oak (Quercus robur) commonly known as the European or English Oak. Both species are native to most of Europe west of the Caucasus and often hybridise in the wild.

You will find Pedunculate Oak in valleys, close to rivers, and on damp, moist land. It is tolerant of extremes in climate, and matures to form a broad and spreading crown with sturdy branches beneath. The sessile Oak is a more modest tree - it thrives on poor acidic soils and is often found in hilly areas. It is not tolerant of flooding.

The leaves of a Pedunculate Oak have no stalk at their base

Oak leaves are 10cm long with 4–5 deep lobes and smooth edges. The leaves of the Pedunculate Oak appear two weeks earlier than those of the Sessile Oak, which have a long leaf stalk whereas he Pedunculate Oaks have a short  or no leaf stalk and 2 ‘earlobes’ at their base. Oak flowers are wind pollinated: the male flowers are yellow-green hanging catkins that appear among the young leaves in late April - early May; the female flowers are small and inconspicuous. The fruits are called 'acorns' and are borne mostly in pairs, each into a cup-shaped base called ‘cupule’. ‘Sessile’ means stalkless and refers to the acorns, which grow directly on the stem of the Sessile Oak; Pedunculate Oaks have stalked acorns.

The male flowers (catkins) on a Pedunculate Oak

Oaks support up to 500 different types of insects, fungi, mammals, mosses and lichens, and creases in their bark provide shelter and home for insects, as do the leaves, buds, and the acorns. Their canopy allows light to pass through, permitting a diverse and enriched under-story. The acorns are a valuable food source for several small mammals and birds, notably Eurasian Jays and Squirrels.

 Green acorns on a Pedunculate Oak - notice the long stalk on which they grow

Oaks can live for over 500 years, and coppiced specimens may reach 1000 years. Every four to ten years, they synchronize to produce almost no acorns at all, only to rain them down excessively the following year, referred to as a 'mast year'.

A Sessile Oak, with long stalks at the base of the leaves, but none to hold the acorns.

The wood from Oak is hard and durable and valued for many purposes. It has a high tannin content, which makes it resistant to insect and fungal attacks and is particularly useful for wine and spirit barrels. In Europe, Oak wood was used for the construction of ships and the principal timber in the construction of timber-framed buildings. Oak galls (also called Oak apples) were used for centuries as a main ingredient in iron gall ink for manuscripts. Acorns are used for making flour, or roasted for acorn coffee.

Oak galls are caused by chemicals injected by the larva of the gall Wasp

The Sessile Oak is the national tree of Ireland and the emblem of Co. Derry, from which its name derives from the Irish Doire - ‘Oak’. Kildare comes from the Irish Cill Dara - church of the Oak or Oak Church.

Is there something you particularly like about the Oak? Or you have a special memory attached to one? I’d love to hear about it in the comments!

📸 Andy Smith, Sten, Franco Folini

1 comment

  • Hi, I found something today ,I’d never seen before and Google Lens told me it was Oak apple Galls. Made from Larvae chemicals. Larvae feed on whatever’s inside of it. Kinda cool, it looks like those plastic Balls with electric light.that when touched,it looks like⚡ out of your fingers.Lol.IDK it looks pretty 🆒 ,is it rare to find. She I be keeping my distance for both our sakes???

    Jeannine Ainsworth

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