Photographer: Wilson Faircloth Affiliation: USDA Agricultural Research Service Source:www.bugwood.org Copyright: CC BY 3.0
Cogongrass (Imperata cylindrica) is known for infesting in dense circular patches that reach an average of 3 to 4 feet in height. During winter months, cogongrass may turn brown, but is dependent on the temperature. The leaves of cogongrass are usually green and begin just above the soil line giving the appearance of no plant stem. Sheaths of the leaves overlap allowing for a round appearance. Leaves do not sprout from one dense clump of growth, but rather from several separate plants that are spread out at the soil. Cogongrass blooms from March to June with a white cylindrical seed head that appears at the opening of the grass blade. Seed heads are silver to white and appear fluffy, similar to dandelion seeds.
Cogongrass is known for its ability to grow in dense mats, preventing growth from other native species of plants. Prevention of native plant growth is facilitated by specialized rhizomes that conserve water and reach depths of 4 feet bellow the soil. Cogongrass is able to become established rapidly and forces out native plants based on increasing mass alone. Native plant species are at risk of sever habitat loss when cogongrass becomes established. Native wildlife also faces habitat loss when available food sources are reduced by an increase in cogongrass.
Seed production occurs in Spring with light fluffy seed heads formed at the top of the plant. Dispersion and spread of cogongrass is facilitated by wind transfer of seeds to new areas. However, it is not entirely clear that seed dispersal is the primary mode of propagation for cogongrass. Short term spread and survival is facilitated by rhizomes that are adapted for water conservation. Rhizomes are produced in mass amounts with one plant capable of releasing 3 tons per acre.
The first introduction of cogongrass in the United States was accidental. In 1912, the grass first appeared in Grand Bay, Alabama as a result of escaped rhizomes from an orange crate packing shipment. In 1921 cogongrass was intentionally introduced to Mississippi as a forage plant from the Philippines, followed by Florida in the 1930's. Cogongrass was eventually placed on the noxious weed list after it was realized that there was no economic value for the plant and it was an aggressive pest.
U.S. Habitat: Cogongrass is only found in the southeast region of the United states where the climate is warm and humid providing moisture and mild winters. Cogongrass can be found in a variety of habitats such as pastures, forests, gardens, roadsides, and vacant fields.
U.S. Present: AL, CT, FL, GA, LA, MS, NC, SC, TN, TX, VA
For a CAPS/CERIS/USDA map of survey and eradication efforts click here.
Also, a map provided by EDDmapS is here.
To effectively remove infestations of cogongrass it is important to detect the plant in early growing stages or when infestations are relatively small. If the infested area is mostly flat and small, tilling the soil beginning in late March can be effective with repeating tilling every 6 to 8 weeks with a soil depth of at least 6 inches. It is important to clean equipment used before tilling other areas to prevent the spread of cogongrass rhizomes to new areas. Mowing can be utilized to keep cogongrass under control, but must be repeated regularly and cut to a short length just above the soil. For areas that are not flat, herbicides containing glyphosate and impazapyr are the most effective.
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