Acorns are the fruit, or nut, of oak trees. Oak trees are native to the northern hemisphere. An acorn usually contains one seed and will mature in six months to two years. Acorns drop from trees in late summer and early fall. Oak trees must produce many nuts because most of the acorns are eaten by insects, birds and animals before they have time to grow.
Most oak seedlings will grow into young trees at the rate of about 30 to 60 cm (1 to 2 feet) every year. Trees can grow upwards of 30 m (100 feet), but some may reach as high as 45 m (150 feet) or more. Trees may live for 200 years, but one has been recorded at more than 1,500 years old--the Seven Sisters Oak in Mandeville, Louisiana.
Production of acorns
Oak trees start producing acorns when they are 20 years old, but sometimes trees will wait until they are 50 years old before their first production of seeds. By the time the tree is 70 to 80 years old it will produce thousands of acorns. Once a tree is about 100 years old, it slows down production and averages about 2,200 acorns a year, according to Arcytech.org
Types of oak trees
There are about 400 species of oak trees. Common types of oak trees include the live oak, sawtooth, pin oak, red oak, white oak, bur oak, overcup oak, scarlet oak and water oak.
A mature oak tree draws up to 225 litres (50 gallons) or more of water per day through its roots. Some of the water evaporates from the leaves, a process called transpiration.
Acorns have been a very important food source to some cultures, including American Indians; the acorns were ground into a meal and were a part of their regular diet. One family might eat 225 Kilogram of acorns or more a year.