Oklahoma “Dirty Dozen” list identifies invasive plant species

There’s 13 invasive plant species in Oklahoma that pose a threat to rangeland and if not controlled, your neighbor. See what those are and what to consider.

December 15, 2025

3 Min Read

INVASIVE PESTS: The “Dirty Dozen,” which technically encompasses 13 invasive plant species ubiquitous across the state, can pose several dangers to rangeland in Oklahoma.Mitchell Alcala, OSU Agriculture

by Dean Ruhl

Are you being a good neighbor?

It’s a question Karen Hickman, professor of natural resource ecology and management and director of the environmental science program at Oklahoma State University, poses while discussing invasive plant species in Oklahoma.

Some of those invasive plants can spread onto neighboring properties, meaning upkeep and removal are important. But the “Dirty Dozen” list, which comprises 13 (not 12) invasive plant species across the state, poses dangers to rangeland in Oklahoma that go beyond just upsetting your neighbors.

“Typically, we care about these invasive species because of the harm to human health, harm to the economy or harm to biodiversity,” Hickman said. 

The 13 species part of the Dirty Dozen include:

• Japanese honeysuckle(Lonicera japonica)
• eastern red cedar(Juniperus virginiana)
• musk (nodding) thistle(Carduus nutans)
• Chinese privet(Ligustrum sinense)
• Russian thistle(Salsola tragus)
• sericea lespedeza(Lespedeza cuneata)
• Hydrilla(Hydrilla verticillate)
• yellow bluestem(Bothriochloa ischaemum)
• field brome(Bromus arvensis)
• salt cedar(Tamarix spp.)
• cheatgrass(Bromus tectorum)
• johnsongrass(Sorghum halepense)
• Siberian elm (Ulmus pumila)

Leaving the plants on your property could result in decreased forage. The plants could be toxic. The invasive species could be detrimental to wildlife habitats, decreasing populations for hunting purposes.

Related:Fungus that attacks Canada thistle could help farmers

Fire dangers can increase, too, if species are left untreated. “We see that a lot with eastern red cedar,” Hickman said.

In addition to being part of the Dirty Dozen, musk thistle also lands on Oklahoma’s noxious weeds list. Scotch thistle and Canada thistle are also considered noxious weeds in Oklahoma. That means landowners are legally required to control, treat or eradicate them. A light infestation is quantified as fewer than two plants per acre, a medium infestation is two to nine plants per acre, and a severe infestation is 10 or more plants per acre.

Properties bordering other states also need to remain aware of what those states have legally defined as noxious weeds. “There are noxious weeds that your Kansas neighbors are going to have to control, and Oklahoma landowners are not legally going to have to,” Hickman said.

What can landowners do?

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How the problematic species are treated will depend on the specific species and the growth stage, Hickman said. She stressed the importance of reaching out to your county OSU Extension office and asking for assistance.

“For instance, if it is eastern red cedar and they are small, you can conduct a prescribed fire safely and burn and kill them all,” Hickman said. “If it’s johnsongrass and it’s totally covering an area, you either are going to have to graze it or spray it with an herbicide.”

Related:Winter menu: Frozen slugs or fresh spring salad bar?

Hickman stressed the importance of reaching out to local Extension educators to decide which herbicide is best, depending on the season and species. Digging the plant up and properly disposing of it is also an option.

Other invasive plant species that aren’t as prevalent across the state can be found on okinvasives.org, where a watchlist for species and the type of land they invade (gardens, rangeland, forested area, etc.) is kept up to date.

The OSU Extension website offers a variety of resources to assist landowners in identifying and treating invasive species. OSU provides information on “plant this, not that” recommendations on all invasive species. Local Extension offices can also help with species and connect people with specialists.

But, as Hickman explained, species on the Dirty Dozen list will never be eradicated from the state.

“We’ve planted them, we’ve spread them,” Hickman said. “Our goal is to increase awareness across the state of these species so that we can protect areas that haven’t been invaded yet.”

Related:Extension will lead Endangered Species Act compliance

Ruhl is the communications coordinator within Oklahoma State University’s Ferguson College of Agriculture Digital Communication and Media Relations. 

Read more about:WeedsNoxious WeedsInvasive Species

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