Oaks are long lived trees, many being 500 or more years old. Oak wood is good to work with, as it cleaves well (picture of grain etc below) but younger wood can stain the hands (due to tannins).
There are two main types / species, Sessile Oak (Quercus petraea) and Pedunculate Oak (Quercus robur), which readily hybridise.
In the pedunculate oak, the leaf stalks (petioles) are quite short (less than 0.5cm) whereas in the sessile oak the leaf stalks are more obvious (1 to 1.5 cm in length).
The edge of the leaf is lobed and wavy. There are 5 to 7 lobes on each side of the leaf. In the pedunculate oak, the lobes tend to taper into the stem so that the leaf stalk / petiole is scarcely noticeable.
Buds, Bark and Stem
Buds tend to be clustered near the end of the winter twig (see right hand image below); they have rusty brown over-lapping scale leaves. The bark is grey and in older trees fissures, and it often supports a rich lichen flora.
The bark of a young oak is shown below for comparison
Flowers and Fruits
When fertilised, these will develop into acorns. The acorns are up to 2-2.5 cm in length, and (in the pedunculate oak) are attached to a peduncle or (3-7cm) acorn-stalk. One to four acorns are attached to each peduncle. In the sessile oak, the acorns appear to sit on the twigs.