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More About the Oak !

An oak is a tree or shrub in the genus Quercus (/ˈkwɜːrkəs/;[1] Latin "oak tree") of the beech family, Fagaceae. There are approximately 500 extant species of oaks.[2] The common name "oak" also appears in the names of species in related genera, notably Lithocarpus (stone oaks), as well as in those of unrelated species such as Grevillea robusta (silky oaks) and the Casuarinaceae (she-oaks). The genus Quercus is native to the Northern Hemisphere, and includes deciduous and evergreen species extending from cool temperate to tropical latitudes in the Americas, Asia, Europe, and North Africa. North America has the largest number of oak species, with approximately 160 species in Mexico of which 109 are endemic and about 90 in the United States. The second greatest area of oak diversity is China, with approximately 100 species.


Oaks have spirally arranged leaves, with lobate margins in many species; some have serrated leaves or entire leaves with smooth margins. Many deciduous species are marcescent, not dropping dead leaves until spring. In spring, a single oak tree produces both male flowers (in the form of catkins) and small female flowers, meaning that the trees are monoecious. The fruit is a nut called an acorn or oak nut borne in a cup-like structure known as a cupule; each acorn contains one seed (rarely two or three) and takes 6–18 months to mature, depending on their species. The acorns and leaves contain tannic acid which helps to guard from fungi and insects.The live oaks are distinguished for being evergreen, but are not actually a distinct group and instead are dispersed across the genus.


Linnaeus described only five species of oak from eastern North America, based on general leaf form. These were white oak (Quercus alba), chestnut oak (Q. montana), red oak (Q. rubra), willow oak (Q. phellos), and water oak (Q. nigra). Because he was dealing with confusing leaf forms, the Q. montana and Q. rubra specimens actually included mixed foliage of more than one species.


How An Oak Tree Benefits The Biosphere

During its life, an oak tree doesn’t just take resources from its local environment to survive. The presence of the tree provides many benefits to the surrounding biosphere and its other inhabitants.


  • Canopy provides shade for other plants and soil, preventing water loss and providing optimum temperature for growth.

  • Each oak leaf absorbs CO2 and releases Oxygen. 240 pounds of Oxygen are released each year from one oak tree, enough for a family of four people. Carbon is retained in the tree structure as it grows, making oak a Carbon neutral crop.

  • Water drawn from the ground is released through leaf pores into the atmosphere and back into the local water cycle.

  • Branches and trunk provide homes for birds, squirrels, insects and fungi.

  • Leaves, sapwood, bark and acorns provide food for other species.

  • Roots bind soil together, preventing erosion and desertification.

  • Roots draw water through the soil, keeping it moist and bound together and providing ideal conditions for other plants. A mature oak can draw 50 gallons of water each day, maintaining the local water cycle.

Even in death, the oak tree continues to benefit the environment. In farmed areas where the oak trees are felled, shavings and sawdust are often returned to the soil to simulate this. Stumps of felled trees also contribute as they decay.


  • The wood and bark of the dead tree can provide food and nourishment for fungi and bacteria.

  • Several species of insect lay eggs in the dead wood, providing shelter and food for their larvae as they mature.

  • Insects living in the dead wood can be a useful food source for birds and bats.

  • The hollow trunk provides shelter from predators for small mammals and birds.

  • As the wood decays, it returns nutrients and moisture to the soil below. This provides a rich environment for future plant growth.

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