Oklahoma is home to a diverse array of plants. There are more than 2,400 different native species of plants found in Oklahoma, including more than 330 native species of trees, shrubs and woody vines. Trees can be identified by the color, structure and magnitude of twigs, the shape, size, placement and coloration of the leaves, the color and texture of the trunk bark and the size, color, number of petals of flowers as well as the shape, size, taste and color of the fruit.
Examine the leaves of the tree. Leaves are one of the best identification tools. Oklahoma has many native trees that are evergreen and retain their leaves all year long. The majority of native evergreen trees are located in the Ouachita Mountains of Oklahoma. Native evergreen trees include eastern red cedar, or Juniperus virginianana; loblolly pine, or Pinus taeda; and pinyon pine, or Pinus cembroides.
Determine if the trees are deciduous, losing their leaves in the fall. Deciduous native trees include black walnut, or Junlans nigra; Chinese pictache, or Pistacia chinensis; American elm, or Ulmus Americana; lacebark elm, or Ulmus pravifolia; bur oak, or Uuercus macrocarpa; Shumard oak, or Quercus shumardii; hackberry, or Celtis occidentalis; Kentucky coffeetree, or Gymncladus dioicus; and western soapberry, or Sapindus drummondii.
Research the shape of the leaves and gather a few samples for study and identification. Leaf margins and the shape of leaves vary greatly among Oklahoma tree species. Leaves may be broad, flat, narrow, oblong, round or heart shaped.
Look at the flowers the tree presents in spring and early summer. Oklahoma is famous for its abundance of brightly colored spring flowering trees. Redbud, or Cercis canadensis, the Oklahoma state tree, may be found throughout the state on the edge of forests, in open meadows and roadside ditches. The redbud tree presents swirls of deep pink flowers in early spring. Redbud is a widely used landscape tree in both county and urban landscapes. Redbud grows from 20 to 30 feet tall at maturity. The small red fruit that develops in early autumn provides winter food for birds and wildlife.
Visit your local county extension agent. A knowledgeable horticulturist can readily identify a tree, if provided a sample of leaves and a branch. County extension agents are familiar with the trees that are native to Oklahoma and can provide a wealth of information on their care, cultivation and identification.
Look at the land where the trees are growing. Oklahoma has a new and strongly emerging forest of eastern red cedar. Over the past 70 plus years, land that was previously open range or pasture is becoming a nursery for a new eco-system. Wildfire suppression, overgrazing of livestock and passive land management has allowed cedar to grow where it was never found before. Three to 4 million acres of land that was previously grass prairie is now scattered with eastern red cedar trees.
Visit the Arbor Day Foundation website at arborday.org to access the interactive tree data base. The foundation also has a wealth of information about tree planting and cultivation. Tree identification books can be purchased from the foundation or are available at most book stores. The Oklahoma Forestry Service also has a helpful Oklahoma tree database. There is a link in the Resources section.