Sweden has two species of oak: pedunculate oak, Quercus robur, and sessile oak, Quercus petraea.The more common one is pedunculate oak, growing up to Värmland and northern Uppland. Sessile oak is found only in southern Gotland. There are also hybrids. The leaves are lobed, smooth and glabrous. Sessile oak keeps its leaves all winter. The fruits are acorns, on the sessile oak growing in clusters, hence the name grape oak. Young trees have smooth, gray bark, while on old specimens it is course and fissured. Oaks have deep and strong side roots which makes them very storm proof. The pedunculate oak can grow 25 meters high and get well over 1000 years old. Sessile oaks do not reach that height or age.
Both species gets tall and straight if growing in dense populations or wide and gnurly if growing alone.
The sapwood is yellowish gray and the heartwood dark brown. The wood has great strength and hardness, is easy to split and is very resistant to decay and rot. It is, among other things, used for ship building, underwater constructions, bridges, interiors, furniture, floors and barrels. The great utility of the oak have sometimes brought it close to extinction. During times when oak was used for war ships only the king (state) could fell an oak.
If oak is kept under water for long time it darkens and is then called black oak. After centuries under water it is still useful for woodworking.
Did you know that:
- The bark is rich in tannins and is used for tanning leather.
- The acorns were used for pig fodder or for baking bread or as coffee substitute.
- Decoctions of the bark cured pain and wounds.
- Norse mythology regards the oak as holy, sacred for the thunder god, Thor. Before Christianity it was a common tree for making sacrifices.