The Oak
The Wood Guide · The forests
Tree portraitThe oak
A symbol of strength and endurance, and the longest-lived tree in our part of the world. It supports more species than any other native tree.
- Quercus robur and petraea
- 500 to 1,000 years
- 30 to 45 metres
The oak in brief
A tree that, down the centuries, has held a special place in almost every European culture — as a boundary tree, a tree of justice, a symbol.
That status did not come out of nowhere. An oak lives five hundred to a thousand years and grows thirty to forty-five metres tall, outliving generations of people. Whoever plants one plants it for someone not yet born.
The secret of that long life lies in slowness and chemistry. The oak grows slowly, which gives narrow growth rings and dense wood, and it fills its heartwood with tannins that keep fungi and insects at bay. That same tannin content puts its wood in durability class 2 — one of the few European species that can go outdoors untreated.
A mature oak is home to hundreds of species of insects, mosses, lichens, fungi and birds — more than any other native tree. Every acorn that is not eaten is also a potential new tree, and jays bury them by the tens of thousands each year. Without jays the oak would spread far more slowly.
- Botanical
- Quercus robur (pedunculate oak), Q. petraea (sessile oak)
- Lifespan
- 500 to 1,000 years
- Height
- 30 to 45 metres
- Leaves
- characteristically lobed
- Fruit
- acorns, in a cup
- Wood
- durability class 2
To be fair: oaks grow slowly, and for a forester that is an economic problem. An oak planted today will only yield saw timber in a hundred years. That is exactly why old oak woods have become scarce in Europe, and why oak costs many times more than softwood.
Pedunculate or sessile oak
| Pedunculate oak (Q. robur) | Sessile oak (Q. petraea) | |
|---|---|---|
| Leaf | Short stalk, small lobes (auricles) at the base | Longer stalk, no auricles |
| Acorns | On a long stalk | Almost stalkless, directly on the twig |
| Site | Moist, rich soil | Drier, poorer and sloping ground |
| Crown | Irregular, broad side branches | Straighter trunk, more regular crown |
| Wood | Slightly coarser | Finer and more even |
Pedunculate oak has acorns on a long stalk and leaves with a very short stalk; sessile oak is exactly the reverse. Once you know that, you can see the difference from ten metres away.
In pictures · An ecosystem on one trunk
Schematic drawing.
An ecosystem on one trunk
Insects
Hundreds of species live on oak leaves, bark or wood. The oak processionary moth is the best known, but the vast majority do no harm.
Birds and mammals
Acorns feed jays, squirrels, mice and wild boar. Hollows in old oaks provide nesting sites for woodpeckers, owls and bats.
Fungi and lichens
A world of its own grows on bark and dead wood. Dead wood in a living oak is not a disease but a habitat.
The jay as planter
A jay buries thousands of acorns every autumn and forgets some of them. That is how the oak spreads further than its own crown reaches.
What the oak gives
Durability class 2
Thanks to the tannins in its heartwood, oak can go outdoors untreated — one of the few European species for which that is true.
Silver figure on quarter-sawn wood
Quarter-sawn oak shows its shiny medullary rays as light flecks. That is the hallmark of classic oak furniture.
Casks and barrels
Oak has vessels sealed with tyloses, which makes it watertight — the reason whisky and wine casks have traditionally been made from oak.
Reacts with iron
The tannins turn black on contact with ordinary steel. Always use stainless fixings.
The full wood guide is at what is oak wood; the difference from American species at European and American oak.
Frequently asked questions about the oak
How old does an oak get?
Five hundred to a thousand years in favourable conditions. There are oaks in Europe that were young trees in the Middle Ages.
What is the difference between pedunculate and sessile oak?
Pedunculate oak has acorns on a long stalk and leaves with a short stalk and auricles; sessile oak has stalkless acorns and longer-stalked leaves. Sessile oak grows on drier ground.
Why does oak turn black around screws?
The tannins in oak react with iron. Use stainless steel or galvanised fixings — ordinary screws leave a black ring within weeks.
Can oak be used outdoors?
Yes, the heartwood reaches durability class 2 and can go outdoors untreated. The sapwood cannot — in almost every species that is class 5.
The oak in perspective
Whoever plants an oak plants for someone they will never meet.
Have a question about your project? Just ask — we're happy to help.