Spotted Knapweed

Spotted knapweed (Centaurea stoebe)

Spotted Knapweed (Centaurea stoebe) Spotted Knapweed (Centaurea stoebe) is native to Eurasia and has become an invasive species in North America.

Spotted Knapweed is considered a problem due to its aggressive growth, rapid spread, and the ability to form dense stands, displacing native vegetation and impacting ecosystems. It is known for its allelopathic properties, releasing chemicals that inhibit the growth of other plants. Additionally, Spotted Knapweed can negatively affect forage quality for livestock.

Effective management strategies for Spotted Knapweed involve a combination of preventive measures, early detection, and control methods. Control may include manual removal, mowing, targeted herbicide application, and the introduction of biological controls, such as insects that feed on the plant. Integrated pest management practices are often recommended to address the invasive nature of Spotted Knapweed. For specific guidance, please refer to the information on the USDA Forest Service website.

Yellow Bluestem

Yellow bluestem (Bothriochloa ischaemum)

Yellow bluestem infographic Yellow Bluestem (Bothriochloa ischaemum) is native to Asia and has become an invasive species in North America.

Yellow Bluestem is considered a problem due to its aggressive growth, rapid spread, and the ability to form dense stands, displacing native vegetation and impacting ecosystems. It is known for its ability to alter fire regimes and negatively affect biodiversity. The grass can outcompete native plants, reducing forage availability for wildlife and livestock.

Effective management strategies for Yellow Bluestem involve a combination of preventive measures, early detection, and control methods. Control may include manual removal, mowing, targeted herbicide application, and the restoration of native vegetation to restore and maintain ecosystem health. For specific guidance, please refer to the information on the USDA Forest Service website.

Yellow Starthistle

Yellow starthistle

Yellow starthistle infographic Yellow Starthistle (Centaurea solstitialis) is native to the Mediterranean region and has become an invasive species in North America.

Yellow Starthistle is considered a problem due to its aggressive growth, rapid spread, and the ability to form dense stands, displacing native vegetation and impacting ecosystems. It is known for its spiny leaves and rapid colonization of disturbed areas, reducing biodiversity and impacting forage availability for livestock.

Effective management strategies for Yellow Starthistle involve a combination of preventive measures, early detection, and control methods. Control may include manual removal, mowing, targeted herbicide application, and the introduction of biological controls, such as insects that feed on the plant. Integrated pest management practices are often recommended to address the invasive nature of Yellow Starthistle. For specific guidance, please refer to the information on the USDA Forest Service website.

Buffelgrass

Buffelgrass (Pennisetum ciliaris)

Buffelgrass infographicBuffelgrass (Pennisetum ciliare), originally from Africa, has become an invasive species in the Southwestern United States. Its rapid spread poses a significant threat to ecosystems, as it outcompetes native vegetation, alters natural fire regimes, and negatively impacts wildlife habitat. Effective management of buffelgrass involves a multifaceted approach, including prevention through public education and responsible recreation, early detection, manual removal, targeted herbicide application, and restoration efforts focused on reintroducing native vegetation and employing adaptive management strategies. Visit the USDA Weed Field Guide for the Southwest Website for comprehensive information on understanding, preventing, and managing buffelgrass to protect the health of Southwestern forests and grasslands.

Credit: USDA Weed Field Guides for the Southwest Region

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Common Sow Thistle

Common Sow Thistle

Common Sow Thistle Infographic

Common Sow Thistle (Sonchus oleraceus) is believed to be native to Europe and has become an invasive species in various parts of the world, including North America.

Common Sow Thistle is considered a problem due to its rapid growth, prolific seed production, and the ability to colonize disturbed areas. It can outcompete native vegetation, impacting biodiversity and disrupting ecosystems. The plant is known for its adaptability to different soil types and climates.

Effective management strategies for Common Sow Thistle involve a combination of preventive measures, early detection, and control methods. Control may include manual removal, mowing, targeted herbicide application, and promoting the growth of desirable native vegetation. Integrated pest management practices are often recommended to address the invasive nature of Common Sow Thistle.

Fountain Grass

Fountain Grass (Pennisetum setaceum)

Fountain Grass (Pennisetum setaceum)

In 2020, Fountain Grass was listed as an Arizona Noxious Weed. This prohibits its sale or import into the state. Native to Africa and the Middle East, Fountain grass has been introduced to many parts of the world as an ornamental grass. Fountain Grass is expanding its range in Arizona and the Southwest. 

Its rapid spread poses a significant threat to ecosystems, as it outcompetes native vegetation, provides fuel for wildfires, and negatively impacts wildlife habitat. Effective management of fountain grass involves a multifaceted approach, including prevention through public education and responsible recreation, early detection, manual removal, targeted herbicide application, and restoration efforts focused on reintroducing native vegetation and employing adaptive management strategies. Visit the USDA Weed Field Guide for the Southwest Website for comprehensive information on understanding, prevention, and the best management practices for managing fountain grass to protect the health of Southwestern forests and grasslands.

Credit: USDA Weed Field Guides for the Southwest Region

Fountain Grass infographic

Fountain grass. Photo courtesy Patti Fenner.

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Giant Reed

Giant Reed (Arundo donax)

Giant Reed InfographicGiant Reed (Arundo donax), believed to be native to the Mediterranean region, has become an invasive species in various parts of the world, including the Southwestern United States. This aggressive plant species poses a significant ecological threat due to its rapid growth, which can lead to the displacement of native vegetation, alteration of stream channels, and increased fire risk. Managing Giant Reed involves a comprehensive approach, including prevention, early detection, and control strategies. Control methods may encompass mechanical removal, targeted herbicide application, and follow-up monitoring to prevent its re-establishment. For detailed guidance on understanding and managing Giant Reed, please refer to the provided link on the USDA Weed Field Guide for this species.

Credit: USDA Weed Field Guide for the Southwest Region

London Rocket

London Rocket (Sisymbrium irio)

London Rocket infographic London Rocket (Sisymbrium irio) is believed to be native to the Mediterranean region and has become an invasive species in various parts of the world, including North America.

London Rocket is considered a problem due to its rapid growth and ability to colonize disturbed areas. It can outcompete native vegetation, negatively impacting biodiversity and disrupting ecosystems. The plant is known for its adaptability to different soil types and its prolific seed production.

Effective management strategies for London Rocket involve a combination of preventive measures, early detection, and control methods. Control may include manual removal, mowing, targeted herbicide application, and promoting the growth of desirable native vegetation. Integrated pest management practices are often recommended to address the invasive nature of London Rocket.

Malta Star Thistle

Malta Star Thistle

Malta StarthistleMalta Star Thistle (Centaurea melitensis) is believed to be native to the Mediterranean region and has become an invasive species in North America.

Malta Star Thistle is considered a problem due to its aggressive growth, rapid spread, and the ability to form dense stands, displacing native vegetation and impacting ecosystems. It is known for its spiny leaves and rapid colonization of disturbed areas, reducing biodiversity and affecting forage availability for livestock.

Effective management strategies for Malta Star Thistle involve a combination of preventive measures, early detection, and control methods. Control may include manual removal, mowing, targeted herbicide application, and the introduction of biological controls, such as insects that feed on the plant. Integrated pest management practices are often recommended to address the invasive nature of Malta Star Thistle. For specific guidance, please refer to the information on the USDA Forest Service website.

Tumbleweed

Tumbleweed (Kali Tragus)

Tumbleweed (Kali Tragus)Tumbleweed, often referring to Russian Thistle in the context of invasive plants, is believed to have originated in Eurasia and has become an invasive species in North America.

Tumbleweed is considered a problem due to its ability to spread rapidly, especially in arid and semi-arid regions. It can outcompete native vegetation, disrupt ecosystems, and contribute to soil erosion. The plant is known for its tumbling habit, dispersing seeds over large distances, leading to its widespread distribution.

Effective management strategies for Tumbleweed involve a combination of preventive measures, early detection, and control methods. Control may include manual removal, mowing, targeted herbicide application, and promoting the growth of desirable native vegetation. Integrated pest management practices are often recommended to address the invasive nature of Tumbleweed.