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   Panicum repens (grass)     
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      Panicum repens habit (Photo: Forest & Kim Starr (USGS)) - Click for full size
    Taxonomic name: Panicum repens L.
    Synonyms: Panicum airoides R. Br. , Panicum aquaticum A. Rich. , Panicum arenarium Brotero , Panicum chromatostigma Pilg. , Panicum convolutum P.Beauv. ex Spreng. , Panicum gouinii (Fourn.), Panicum hycrocharis Steud. , Panicum ischaemoides Retz. , Panicum kinshassense Vanderyst , Panicum leiogonum Delile , Panicum littorale C.Mohr ex Vasey , Panicum nyanzense K.Schum. , Panicum roxburghianum Schult. , Panicum sieberi Link , Panicum tuberosum Llanos , Panicum uliginosum Roxb. ex Roem. & Schult.
    Common names: canota (Spanish), couch panicum, creeping panic, kriechende Hirse (German), millet rampant (French), panic rampant (French), torpedo grass, torpedograss, Victoria grass, wainaku grass
    Organism type: grass
    Panicum repens is a perennial grass that frequently forms dense colonies and has long, creeping rhizomes. It grows in moist, often sandy soils and its rhizomes often extend several feet out into the water. Panicum repens frequently forms dense floating mats that impede water flow in ditches and canals and restrict recreational use of shoreline areas of lakes and ponds. Management of Panicum repens involves the repeated application of herbicides. There is very little physical management that can be used to control Panicum repens, as disturbance encourages its growth.
    P. repens is a perennial grass that frequently forms dense colonies and has long, creeping rhizomes. Flowering stems are erect and up to 0.8m tall. The lower stems sometimes lack leaf blades and consist of only sheaths. Leaves of the upper stem have sheaths and blades. The blades are relatively short, flat or sometimes folded and from 2 to 5mm wide. The inflorescence is a loose, open panicle that is 3 to 10cm long that has weakly divergent to ascending branches. Spikelets are about 2.5mm long (ERDC, UNDATED).
    Occurs in:
    coastland, lakes, riparian zones, water courses
    Habitat description
    ERDC (UNDATED) reports that, "P. repens grows in moist, often sandy soil along beaches and dunes, margins of lagoons, marshy shorelines of lakes and ponds, drainage ditches and canals. Its rhizomes or runners often extend several feet out into the water, and the plant frequently forms dense floating mats."

    Brecke et al. (2001) state: "P. repens is a perennial weed that can be found along ditch banks, around ponds, along roadsides, and in managed turfgrass areas, including golf courses (McCarty et al. 1993). This exotic grass persists in terrestrial, wetland, and aquatic environments of tropical and subtropical regions around the world (Sutton 1996). It has spread throughout the gulf coast region from Florida to Texas (McCartyet al. 1993; Murphy et al. 1992). It is a serious problem in the lower coastal plain of Alabama and Mississippi, and in much of Florida where it is primarily a weed of moist, sandy soils, but it can also grow in finer textured soils (Wilcut et al. 1988)."

    General impacts
    ERDC (Undated) reports that, "The dense floating mats of P. repens may impede water flow in ditches and canals and restrict recreational use of shoreline areas of lakes and ponds." The Florida Exotic Pest Plant Council (FLEPPC, 2003) states that, "P. repens has been reported as a weed of 17 crops in 27 countries, and is considered one of the most serious grass weeds." The authors go on to state that, "P. repens quickly forms monocultures that displace native vegetation, particularly in or near shallow waters." Avid (1999) reports that, "P. repens formed dense monotypic stands in response to increased hydroperiod (depth and duration of flooding)." Brecke et al. (2001) states that in Florida, "P. repens is very competitive and has reduced common bermudagrass (Cynodon dactylon (L.) Pers.) growth by nearly 40% after 2 yr (Wilcut et al. 1988). Tillage will not control P. repens, and may in fact serve to spread the weed to previously un-infested areas (Holm et al. 1977 )." Williamset al. (2003) states that, "Because of the lack of apical dominance, every node along the entire rhizome may sprout nearly simultaneously (Wilcut et al. 1988 )."

    Smith et al. (2004) state that, "On Lake Okeechobee the ability of P. repens to disperse and become established at different water depths was evaluated in a series of experimental pond studies. These studies revealed that fragments remain buoyant for extended periods and so facilitate the dispersal of P. repens within the lake. If fragments become anchored to sediment that is either exposed or in shallow water, they can readily root and establish mature plants; Once established, P. repens can thrive in depths of 75cm or less and can survive prolonged exposure to flooding depths greater than I m. In this manner, low water periods can contribute to the dispersal and colonization pattern of P. repens in the lake. When coupled with lake elevation data, these findings suggest that low water levels or draw downs would increase the marsh area susceptible to P. repens invasion."

    Hossain et al. (2001b) state that, "P. repens is also recognized as a pasture grass, and it could be harvested five to seven times a year in tropical and subtropical areas. A higher amount of rhizomes and roots makes a loose mat-like structure in soil up to 50cm in depth, and indicates that this species could be used for soil erosion control."
    Geographical range
    Native range: Africa, Asia, and Europe (USDA-GRIN, 2003)
    Known introduced range: North America (USDA-NRCS, 2002)
    Introduction pathways to new locations

    Local dispersal methods
    Agriculture (local):
    Natural dispersal (local):
    Management information
    For details on management of this species including physical, chemical and biological control please read our pdf file on management information.
    FLEPPC (2003) states that, "P. repens is tolerant of drought and partial shade, and can grow on heavy upland soils, but thrives in moist to wet sandy or organic soil."
    Brecke et al. (2001) state that, "P. repens rhizomes have the potential to regenerate and produce dense stands from small fragments. Due to the lack of apical dominance, each node has the unique ability to produce axillary buds along the entire rhizome (Wilcut et al. 1988 ). Emergence of new shoots from buried rhizome fragments occurs from as deep as 50cm (Hossain et al. 1999 )." FLEPPC (2003) report that P. repens's growth rate is stimulated by tilling and fertilization, and reproduces principally by rhizome extension and fragmentation.
    Lifecycle stages
    Hossain et al. (2001a) state that, "P. repens propagates mainly by rhizomes, which are difficult to control when well established. P. repens develops rhizomes when around 50 days old in the summer season (24-30°C), and primary and secondary branches of the rhizome usually develop 70 and 130 days after planting (DAP), respectively. Rhizomes can penetrate into soil up to 50cm deep, and they require up to 120 days after planting to complete emergence depending on their burial depth. A single culm emerging from a single rhizome bud produced about 23,000 rhizome buds in 1 year. The biomass of P. repens increases rapidly from 50 DAP with the increasing number of rhizome buds and shoots."
    Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
    Last Modified: Wednesday, 4 October 2006

ISSG Landcare Research NBII IUCN University of Auckland