Johnsongrass
Place of Origin: Mediterranean
Place of Harm: All 6 continents (all of US), major islands
First Introduced: 1840
Harms: Agriculture, livestock (if eaten), plants
Other Names: Aleppo grass, Aleppo milletgrass, Egyptian millet, Egyptian grass, millet grass, Morocco millet, grass sorghum, false guinea grass, Means’ grass
Taxonomy: Poales, Poaceae
Johnsongrass is a perennial monocot grass originally introduced as forage. It can grow up to 8 ft. The rhizomes extend to 20 in. It lives in crop fields, abandoned fields, pastures, forest edges, and riparian areas. It grows best in open, disturbed, and high-nutrient land, especially crop fields. It is considered one of the ten worst weeds in the world. It quickly forms dense monotypic stands that compete with agricultural cash crops, driving them out and taking over the fertile soil; it can reduce crop yields to 10% the norm with allelopathy. A very aggressive invader, it reduces diversity and has a resistance to glyphosate. When under stress (heat, cold, or cutting periods), the leaves produce hydrogen cyanide, a deadly chemical that bloats and kills livestock if it is consumed enough. Also, Johnsongrass can cross-breed with cultivated sorghum (Sorghum sudanese), creating a hybrid that is also a dangerous weed . Control methods for small areas include hand pulling in June, after rain when the ground is soft. Remove all plant roots; it has strong regenerative ability. For large areas, use glyphosate or selective herbicides like primisulfuron to protect crops. Repeated mowing kills seedlings, prevents seeding, and reduces regrowth. Repeated tilling prevents root development and reduces populations, but moderate early season tillage encourages growth by spreading pieces. Intense grazing in combination with tilling, herbicides, and planting competitive species (alfalfa) works best. Cutting seedheads in early July is effective if repeated for several years. The rhizomes live over winter and in the spring send out white shoots. The grass leaves emerge late in spring and the plant forms seed by late July. A single plant can produce over than 80,000 seeds annually. The best plants can flower in 6 weeks (early July) and have mature seeds just 2 weeks later; their seeds start sending out rhizomes within 3 weeks of sprouting. Seeds are hardy and can stay viable for 3 years. The plant dies after the first frost, but creeping rhizomes propagate vegetatively. The rhizomes grow very fast. Similar native species include Indiangrass (Sorghastrum nutans) and switchgrass (Panicum virgatum). Johnsongrass was originally brought here for forage and erosion control reasons. It is a good forage due to its persistent qualities. It was named after Colonel William Johnson, who introduced this species to his Alabama farm in around 1840.
Place of Origin: Mediterranean
Place of Harm: All 6 continents (all of US), major islands
First Introduced: 1840
Harms: Agriculture, livestock (if eaten), plants
Other Names: Aleppo grass, Aleppo milletgrass, Egyptian millet, Egyptian grass, millet grass, Morocco millet, grass sorghum, false guinea grass, Means’ grass
Taxonomy: Poales, Poaceae
Johnsongrass is a perennial monocot grass originally introduced as forage. It can grow up to 8 ft. The rhizomes extend to 20 in. It lives in crop fields, abandoned fields, pastures, forest edges, and riparian areas. It grows best in open, disturbed, and high-nutrient land, especially crop fields. It is considered one of the ten worst weeds in the world. It quickly forms dense monotypic stands that compete with agricultural cash crops, driving them out and taking over the fertile soil; it can reduce crop yields to 10% the norm with allelopathy. A very aggressive invader, it reduces diversity and has a resistance to glyphosate. When under stress (heat, cold, or cutting periods), the leaves produce hydrogen cyanide, a deadly chemical that bloats and kills livestock if it is consumed enough. Also, Johnsongrass can cross-breed with cultivated sorghum (Sorghum sudanese), creating a hybrid that is also a dangerous weed . Control methods for small areas include hand pulling in June, after rain when the ground is soft. Remove all plant roots; it has strong regenerative ability. For large areas, use glyphosate or selective herbicides like primisulfuron to protect crops. Repeated mowing kills seedlings, prevents seeding, and reduces regrowth. Repeated tilling prevents root development and reduces populations, but moderate early season tillage encourages growth by spreading pieces. Intense grazing in combination with tilling, herbicides, and planting competitive species (alfalfa) works best. Cutting seedheads in early July is effective if repeated for several years. The rhizomes live over winter and in the spring send out white shoots. The grass leaves emerge late in spring and the plant forms seed by late July. A single plant can produce over than 80,000 seeds annually. The best plants can flower in 6 weeks (early July) and have mature seeds just 2 weeks later; their seeds start sending out rhizomes within 3 weeks of sprouting. Seeds are hardy and can stay viable for 3 years. The plant dies after the first frost, but creeping rhizomes propagate vegetatively. The rhizomes grow very fast. Similar native species include Indiangrass (Sorghastrum nutans) and switchgrass (Panicum virgatum). Johnsongrass was originally brought here for forage and erosion control reasons. It is a good forage due to its persistent qualities. It was named after Colonel William Johnson, who introduced this species to his Alabama farm in around 1840.
Essential Question
"Could a genetically engineered invasive species potentially be used in warfare?"