Iowa State Tree
Oak (common name)
genus Quercus (scientific name)
Oak forests cover an extensive area in the Central and Eastern states and contain one of the most important groups of tree species in the United States. In 1961, Iowa chose oak as its state tree, but no species of oak has been designated. Many authors have listed bur oak, white oak, or northern red oak as the state tree of Iowa. In 2004, oak was adopted as the official national tree of the United States, also with no species designated.
Oak is the largest tree genus in the United States and is the most important hardwood. There are 58 recognized native oak tree species in the United States and Canada, one naturalized tree species, and about 10 native oak shrubs. The bur oak (Quercus macrocarpa) is grown in the National Grove of State Trees to represent Iowa. The natural range of bur oak is chiefly the east-central United States, and it is one of the most common naturally occurring trees in Iowa. It is very drought tolerant and resistant to fire. This allowed the bur oak to grow as the last forest tree on the edges of the prairie, where recurring fires and drought prevented forestation. Bur oak grows to be a stately tree, but it is not used often in horticulture as it is difficult to transplant, and the oversized acorns become potent missiles when they fall. The information that follows concerns oak generally, and when specific, concerns bur oak.
Bur oak is a spreading, deciduous, large shrub to large tree. Branches are low and stout, and the crown is generally open, broad, and round. Leaves are variable, although generally large, and deeply divided into five to nine rounded lobes. Some oaks have serrated leaves. Fruits are relatively large acorns. They are partly or entirely enclosed in a fringed or mossy cap.
Height: up to 170 ft (52 m)
Diameter: 3-7 ft (0.9-2.1 m)
Bark: thick, fire-resistant
Fruit: acorns up to 2 in (5 cm) long
Leaves: 2-10 in (5-25 cm) long, 5-9 round lobes
Bur oak is slow growing and long lived, sometimes reaching 200 or 300 years of age.
Oaks are important components of northern hardwood, lowland hardwood, and southern pine forests, and forests of moderate moisture.
IMPORTANCE TO LIVESTOCK AND WILDLIFE
Acorns of oak trees are a primary source of food for many animal and bird species.
OTHER USES AND VALUES
Oaks are known for their beauty and are highly sought after for lawn and shade trees.
The wood of oak species has long been valued for its durability, strength, and beauty. It is used in products ranging from fine furniture to rough construction material, railroad crossties, interior paneling, and mine props. Barrels for aging red wines, sherry, brandy, and whiskey are made from European and American oak. Oak wood is very resistant to insect and fungal attack because of its high tannin content. It also has very attractive grain markings.
While the wood of oak resists fungus, living trees are sometimes afflicted by it. A phenomenon known as sudden oak death was first reported in 1995 in central coastal California. Since then, tens of thousands of tanoaks, coast live oaks, and California black oaks have been killed by a newly identified fungus, Phytophthora ramorum. On these hosts, the fungus causes a bleeding canker on the stem. The pathogen also infects a variety of other trees. This disease occurs only on the West Coast.
Bur oak reproduces both sexually and vegetatively. Trees are wind pollinated. Minimum seed-bearing age is 35, with optimum seed production occurring between 75 and 150 years of age. In many areas, relatively few seedlings are produced from acorns, and vegetative regeneration is much more common. Bur oak sprouts vigorously after fire or other disturbance.
Oaks are the major component of eastern deciduous forests and dominate stands in central and southern upland forests. Much of that area is encompassed by the oak-hickory type.
Oaks grow in mixed bottomlands in the eastern and southern United States. They are found in valleys and on slopes in the semi-arid regions of the western United States. They are not found in the Great Plains region.
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U.S. Forest Service
U.S. National Arboretum
U.S. Department of Agriculture
Author: World Trade Press