The Dirty Dozen Poster

An educational poster was developed by the Oklahoma Invasive Plant Council to illustrate to Oklahomans the worst, both economically and ecologically, invasive plants in our state.

Dirty Dozen PosterPosters are free – Request one today!

Species Illustrated on the Poster

In the early 1900’s, Yellow Bluestem (Bothriochloa ischaemum) was introduced from Southern Europe and Asia for livestock forage and erosion control. Today, this exotic grass is prevalent throughout the state, altering soil conditions and microorganisms as well as suppressing important native grasses with the end result of decreasing the diversity of native animal communities

Over the past 60 years Field Brome (Bromus arvensis) has been outcompeting desirable vegetation for water and soil nutrients, inevitably decreasing biodiversity in native ecosystems. Field brome was originally introduced from Eurasia for the purpose of erosion control and use as a cover crop. This species is now scattered throughout Oklahoma, with the exception of the northeast corner.

Cheatgrass (Bromus tectorum) is not only spreading across Oklahoma, but all of North America as well.  It was originally introduced when used as a transport packing material from the Mediterranean region of Europe. This aggressive species is notorious for forming monocultures and completely displacing native species as well as decreasing crop production.

Musk/Nodding Thistle (Carduus nutans) was accidentally introduced, possibly through ballast water or as seed contaminant in the late 1800’s. It is mainly found in the north half of the state, east of Woodward, and scattered throughout south central and extreme southeast Oklahoma. Musk/nodding is a listed noxious weed in Oklahoma, due to the its ability to crowd out native vegetation and forage for livestock and wildlife.

Eastern Redcedar (Juniperus virginiana) has become a common evergreen woody species found across the state. Even though this species is native to parts of Oklahoma, fire suppression and planting, as shelterbelts and to screen visability, has allowed Eastern Redcedar to dominate habitats where it should not be found. Dense stands of cedar force out native grass and woody species, decreasing biodiversity and increasing fuel loads which increase the risk of wildfire.

In 1899, Sericea lespedeza (Lespedeza cuneata), a native to China and Japan, was planted for erosion control and as an additional food source for Bobwhite Quail. It has now spread throughout the state, except the panhandle, proven to not be a good food source for Bobwhite Quail, and is rapidly outcompeting and displacing native herbaceous and woody species, destroying habitat quality for wildlife and forage production for livestock.

The Chinese Privet (Ligustrum sinense) was brought from China as an ornamental shrub, but was discovered to form dense thickets, shading out native species of the understory. This exotic plant can now be found in the eastern third of Oklahoma and scattered in the southwest part of the state.

Japanese Honeysuckle (Lonicera japonica) was imported for deer browse, erosion control, and as an ornamental in the early 1800’s. Today, this evergreen vine from Japan inhabits the eastern half of the state as well as Jackson, Caddo, Comanche, Grady, and Ellis counties, overtaking native herbaceous and woody vegetation

In the 1870’s the prickly Russian Thistle (Salsola tragus) was accidentally introduced from Eurasia as a seed contaminant in flax seed. This species becomes the tumbleweed that clog fence lines and host leafhopper species which carry Curly Top virus in multiple crop species. It is now found in the western half of the state and panhandle, as well as Bryan and Muskogee counties.

Johnsongrass (Sorghum halepense) was popularized as livestock forage and for hay production, but under certain conditions it can actually become toxic to livestock. It was introduced from the Mediterranean region around the 1830’s, and has now spread across the entire state of Oklahoma. It invades all stages of rangeland succession, reducing biodiversity and habitats for many species of wildlife.

Saltcedar (Tamarix spp.) is an eastern Asian shrub that was brought in as an ornamental and for erosion control. Originally introduced in 1823, Saltcedar has now spread statewide altering streamflow and overtaking many food producing pants for wildlife as well as other native wetland and floodplain plants that wildlife depend on for habitat.

Siberian elm (Ulmus pumila) is native to China, Siberia, and Turkestan but was brought to America in the 1860’s as a replacement for the American Elm after the breakout of Dutch Elm disease. It is now found to alter wildlife habitat and impact native floodplain vegetation water usage. Today, Siberian Elm can be found in Woods, Woodward, Alfalfa, Cleveland, and Mayes counties.