Iowa State Tree: Oak

Oak is Iowa's official state tree. The legislature designated the genus Quercus without naming a specific oak species. This makes Iowa unusual among U.S. states. Most states specify a particular species for their state tree, unlike Iowa's broader ecosystem framing seen with Iowa's state flower, the Wild Prairie Rose.

Twelve oak species grow native in Iowa. These include white oak, bur oak, red oak, pin oak, black oak, chinkapin oak, swamp white oak, and others. All twelve species technically represent Iowa's state tree.

Bur oak is commonly recognized as Iowa's state tree. It is the only oak species found throughout all 102 Iowa counties. Many people consider it the unofficial representative of Iowa's oak designation.

The common name is simply Oak. The scientific designation is Quercus spp., where 'spp.' indicates multiple species. This genus-level designation differs from typical state tree laws.

The bur oak, often considered Iowa's representative oak, is scientifically named Quercus macrocarpa. Other common Iowa oaks include white oak (Quercus alba), red oak (Quercus rubra), and pin oak (Quercus palustris).

Iowa's path to adopting a state tree involved two legislative attempts. In 1959, House Joint Resolution No. 5 proposed designating bur oak (Quercus macrocarpa) specifically. The resolution got stuck in committee. When the Legislature adjourned on May 7, 1959, the bur oak proposal died.

Two years later, a different approach succeeded. House Joint Resolution No. 10 proposed designating 'THE OAK' without specifying a species. The 59th Iowa General Assembly passed this broader designation. Governor Norman A. Erbe signed it on March 13, 1961.

The legislature chose oak for its abundance and wildlife value. The official statement said oak was abundant and provided shelter, food, and nesting cover for wildlife. No species was named, avoiding the controversy that blocked the 1959 attempt and aligning with values expressed in Iowa's state motto.

Iowa's native oaks divide into two groups: white oaks and red oaks. White oaks include white oak, bur oak, chinkapin oak, dwarf chinkapin oak, swamp white oak, and post oak. These have rounded leaf lobes and acorns that mature in one season.

Red oaks include red oak, pin oak, black oak, northern pin oak, shingle oak, and blackjack oak. These have pointed, bristle-tipped leaf lobes. Their acorns require two seasons to mature.

Bur oak grows throughout the entire state. White oak is found in the eastern two-thirds. Pin oak is native to the southeast quarter. Post oak appears only in four counties, making it the rarest.

Iowa's state flower is the Wild Rose, designated in 1897. The legislature chose wild rose after it appeared on silver service presented to the battleship USS Iowa in 1896. Like the state tree, no specific rose species was designated. The Wild Prairie Rose (Rosa pratincola) is most commonly recognized, and the same landscapes support Iowa's state bird, the American Goldfinch.

Oak leaves are the primary identification feature. White oaks have rounded lobes without bristles. Red oaks have pointed lobes with bristles at the tips. Bur oak leaves have the deepest lobes, sometimes cut nearly to the midrib.

Acorns distinguish oaks from all other trees. White oak acorns have caps covering one-quarter to one-third of the nut. Bur oak acorns have distinctive fringed caps. Red oak acorns have flatter caps and take two years to mature.

Bark varies by species. Bur oak develops bark with deep furrows and ridges. White oak has light gray bark with scaly ridges. Pin oak bark stays relatively smooth longer. Black oak has dark, blocky bark.

Oak acorns provide crucial food for Iowa wildlife. Deer, wild turkeys, pheasants, quail, wood ducks, raccoons, squirrels, chipmunks, blue jays, nuthatches, grackles, and woodpeckers depend on acorns. White oak acorns taste less bitter and are preferred by many animals.

Oak trees provide nesting sites for numerous bird species. Woodpeckers excavate cavities in dead branches. Squirrels build leaf nests in oak canopies.

Oak woodlands offer shelter and cover. It is difficult to find natural woodland in Iowa without at least one oak species. Oak abundance makes them critical to forest ecosystems.

Oak is often associated with strength and endurance. The genus-level designation shows Iowa's appreciation for oak diversity rather than favoring one species. The choice to designate all oaks equally honors the ecological importance of the entire oak group, and regional comparisons are easier with States Neighboring States.