Oak Tree Fruit Acorn

The oaks (Quercus) are a genus of plants in the beech family (Fagaceae). Oak species are deciduous or evergreen trees, rarely also shrubs. The alternate and spirally arranged leaves are usually divided into petiole and leaf blade. The thin to leathery, simple leaf blades are lobed or unlobed. Leaf margins are smooth or toothed to spiny-toothed. The inconspicuous, extrapetiolar stipules drop early. Depending on location and variety, an oak can grow to be about 30 to 40 feet tall and in some cases over 1000 years old. From ancient times, people have noticed that oaks harbor an unusual diversity of insects (up to 1000 species in a crown).

Specialization of numerous insect species on Quercus species is considered to be a sign of high developmental age (coevolution). Many oak species (especially cork oaks and Mediterranean Californian oak species) are well adapted to fires due to their thick and well regenerating bark. In addition, their acorns germinate well and readily on burned, competition-free soil, making them typical species of subtropical fire ecosystems. Oak species are food habitat of caterpillars of many butterfly species. It is surpassed in Central Europe only by the sal willow.