Official Oklahoma State Flower

Mistletoe

(Phoradendron serotinum)

Adopted in 1893.

Mistletoe, Phoradendron seotinum, is the oldest of Oklahoma's symbols, adopted first in 1893, 14 years before statehood. Its greenery in the harsh winter months symbolizes the perseverence of early settlers. The colors of the foliage of mistletoe and its berries, green and white, are the state colors of Oklahoma.

Mistletoe phoradendron serotinum the oldest of Oklahoma's symbols, adopted in 1893 - 14 years before statehood. Mistletoe grows on trees throughout the state and is particularly bountiful in the southern regions of Oklahoma. The dark green leaves and white berries show up brightly during the fall and winter in trees that have shed their own leaves.

Mistletoes are a group of vascular, flowering plants that parasitize stems of trees and shrubs. There are 700-1400 species (depending who you ask) of mistletoe worldwide found in the Viscaceae and Loranthaceae families, located mainly in tropical and subtropical regions of the world. Even the family has several synonyms. Renamed by our own Dr. James Reveal as Phoradendron leucarpum (Johnston and Reveal), American mistletoe was previously know as P. serotinum, P. flavescens. Phoradendron has a wide geographic distribution and is found in the US from New Jersey to Florida to Texas. It has a broad host range and parasitizes mostly hardwoods.

Two genera of mistletoes grow in the United States: the "dwarf mistletoes" (genus Arceuthobium),and the "true mistletoes" (genus Phoradendron). An introduced mistletoe, the European Viscum album, has been found only in northern California--the apple growing region around Sebastopol and Santa Rosa. This mistletoe was presumably brought into this area inadvertently in the early 1900's on apple stock from Europe. Since then, it has spread over about a 16 square mile area, and is found on at least 20 other native and introduced hardwood tree and shrub species.

This family is characterized by semiparasitic plants, attached to trees or shrubs by haustoria, lacking ordinary roots, but having green (chlorophyllous) leaves and stems; leaves: opposite; flowers: inconspicuous; ovary: inferior; stamens: as many as and opposite the perianth-lobes.

The mistletoes are green, flowering plants that require a living host. Some are rather specific and grow on only a single genus of tree; others occur on a wide range of hardwood species. Even though they are completely parasitic, they do manufacture much of their own food materials by photosynthesis and in general require only water and mineral elements from the host plant. In the absence of the green aerial portions of the mistletoe plant, how ever, the root system of the parasite can utilize host nutrients and remain alive within an infected branch for many years. The mistletoes are dioecoius in that male and female flowers are borne on separate plants. Because male and female flowers are so similar in appearance it is difficult to tell the sex of the plant unless fruit are present.

Mistletoe infections are spread mainly by birds (robins, bluebirds, thrushes, cedar waxwings, phainopeplas) that feed on the berries. The berries are round, white to pink in color, occur in spikes and are about one-quarter inch in diameter. A berry usually holds a single seed surrounded by a sticky pulp. Birds digest the pulp of the berry and excrete the living seed. By this means seeds are often deposited on susceptible trees. A viscous coating and hair-like threads on the outer surface of the seeds attach excreted seeds firmly to tree branches. Upon germinating, the growing radicle becomes tightly pressed to the branch surface. Young or small trees are seldom infected by mistletoe. In nearly all cases, initial infection occurs on larger or older trees because birds prefer to perch in the tops of taller trees. Severe buildup of mistletoe often occurs within an infected tree because birds are attracted to and may spend prolonged periods feeding on the mistletoe berries.

Infection takes place by means of a specialized, penetrating structure that forces its way through the bark and into the living host tissues. Once infection has occurred, the root system of the parasite grows within the branch. The aerial shoot system begins to develop shortly after the root system is well established. Often several years are required after infection for a new seed bearing plant to develop. The parasite usually does not spread rapidly, but once a plant is established, the root system gradually extends up and down the branch. Defoliation or destruction of the aerial portion does not kill the mistletoe. New shoots may be produced from the root system or the parasite may survive and grow entirely within the infected host tissues. Not until the tree dies, or the infected portion dies or is removed, is the mistletoe killed.

The mistletoes are rather intolerant of cold and near their northern limits aerial shoots are frequently killed by low winter temperatures