Paspalidium geminatum
(Egyptian paspalidium)

Preferred Scientific Name

• Paspalidium geminatum (Forsskål) Stapf

Preferred Common Name

• Egyptian paspalidium

Other Scientific Names

• Echinochloa geminata (Forsskål) Roberty
• Panicum brizoides Lamarck
• Panicum fluitans Retzius
• Panicum geminatum Forssk.
• Panicum paludivagum Hitchc. & Chase, Contrib.
• Panicum paspalodes Persoon
• Paspalidium geminatum subsp. paludivagum (Hitchc. & Chase) Catasús
• Paspalidium geminatum var. paludivagum (Hitchc. & Chase) Gould,
• Paspalidium paludivagum Parodi
• Setaria geminata (Forsskål) Veldkamp.
• Setaria geminata var. paludivaga (Hitchc. & Chase) R. D. Webster

International Common Names

• English: watercrown grass

Local Common Names

• Mali: baugassongau; marbéré
• Nigeria: angarago; geron tsíntsííyáá; hákóórín karee; mákòòrín karee; tùmbín kúúsúù
• USA: alligator grass; Egyptian panic grass; water paspalidium
• USA/Florida: Kissimmeegrass

• Domain: Eukaryota
•     Kingdom: Plantae
•         Phylum: Spermatophyta
•             Subphylum: Angiospermae
•                 Class: Monocotyledonae
•                     Order: Cyperales
•                         Family: Poaceae
•                             Genus: Paspalidium
•                                 Species: Paspalidium geminatum

Paspalidiumgeminatum was discovered in 1761 by Pehr Forsskål during the first year of a Royal Danish natural history expedition to Egypt and Yemen. The collection was made near the town of Rashid, also called Rosetta, in the Nile Delta region of northern Africa. The holotype remains at the Natural History Museum of Denmark, Copenhagen (view specimen at: http://plants.jstor.org/specimen/c10002722).

Years later Forsskål’s vouchers were reassembled and published by Niebuhr who, assuming editorship only, placed Forsskål as author of the work (Forsskål, 1775; Friis, 1983). Forsskål’s name, Panicumgeminatum, was retained for the holotype.

The current, globally accepted name is Paspalidiumgeminatum (Forssk.) Stapf, first published in volumes nine of ten of the multi-authored Flora of Tropical Africa (Prain, 1920), produced between 1868-1937. The authority Otto Staph, a specialist in the Poaceae of the Old World Tropics (Anonymous, 1933), distinguished the new genus Paspalidium from Panicum.

Subsequent changes in the use of genera stem from disagreement among grass specialists on the separation of Paspalidium from Setaria, as characterized by inflorescence structure, including the presence of a point extending beyond the terminal spikelet, spikelets and bristles (Webster 1987, 1993; Hitchcock and Chase, 1910). Veldcamp (1994) concluded as well that, based on natural gradations in key character traits, Paspalidium cannot be distinct from Setaria, thus explaining his 1994 application of the name Setaria geminata (as used by PROTA4U; PROTA, 2014). Such nomenclatural changes, however, have little bearing on field or in-hand identification of the species and its distinction from closely related taxa, which are typically accomplished under the genus Paspalidium.

Infra-specific entities have been presented, primarily from western hemisphere material (see Identity section table), yet the general consensus remains to treat all as conspecific with the species Paspalidium geminatum (Forsskål) Stapf (see Similarity to other Species to distinguish taxonomically related species).

The internationally preferred common name, Egyptian paspalidium, originates from the locality of the type specimen. Some of the locally used common names include the West African hákóórín kàréé, which translates as ‘dog’s tooth’ (Burkill, 1985), well suited to the enamel-like fruits of ripe spikelets. Another name from the same region is tùmbín kúúsúù, which equates to ‘mouse’s stomach’, though the meaning may be lost in translation (Burkill, 1985). In central Florida fishermen and biologists use the name Kissimmeegrass for offshore stands in large lakes of the Kissimmee River basin.

Description taken from GrassBase (Clayton et al., 2006) with minor modifications from Godfrey and Wooten (1979) and from material reviewed by the author:

A wholly glabrous, perennial grass spreading from culms bending and rooting at lower nodes. Culms compressed above, becoming hollow and inflated, ascending and emergent to 100cm, green sheaths tight, becoming dry and ragged, blades flat to folded and tapering to the tip, inflorescence elongated, flattened, and unbranched, sparingly composed of short, upright to appressed racemes (10-18) on which the ovate spikelets are alternately arranged.

Rhizomes: creeping or floating, spongy to a degree, sometimes in floating mats.

Culms: decumbent, spreading and rooting at the lower nodes; stems slender or to 1 cm across basally, compressed, ascending and emergent from 10 to 100 cm or even higher, hollow and inflated below.

Leaf sheaths: tightly wrapped, later becoming swollen and ragged; often longer than the internodes, glabrous.

Ligule: a ring of hairs up to 1 mm long.

Leaf blades: up to 45 cm long and 17 mm wide, long-tapering, linear, flat to convolute, the long tapering tips involute; mostly glabrous (or with minute hairs at base of upper surface); margins scabrous. Basal leaves do not differ from stem leaves.

Inflorescence:  
Principle axis 5–30 cm long; flattened, unbranched. Rachis narrowly winged; with sharp-edged midrib; angular; 0.5–1 mm wide; terminating in a barren, inconspicuous extension; bearing alternately, relatively short-ascending or appressed-ascending, spikelike fertile branches (racemes).
Racemes flattened; unilateral; 0.5–4 cm long carrying spikelets, alternate in two rows on one side of the 3-angled rachis, the apex shortly pointed and free beyond the seating of the uppermost spikelet (not bristle-like).

Fertile spikelets: sessile or pedicelled; 1–2 in the cluster, pedicels oblong, 0.5–0.75 mm with tiny spines. Spikelets comprising 1 basal sterile florets; 1 fertile florets; without rachilla extension. Spikelets ovate to oblong-elliptic; dorsally compressed; 1.6–3.3 mm long (and longer); falling entire.

Glumes: glumes dissimilar; shorter than spikelet; thinner than fertile lemma. Lower glume short, as broad as they are long or broader than long, somewhat orbicular, apex truncate; 0.5 – 1mm long; 0.2–0.4 length of spikelet; membranous; pallid; without keels; 0–5 -veined. Upper glume elliptic; 0.6–0.8 length of spikelet; membranous; without keels; 5 -veined. Upper glume lateral veins transversely connected at apex. Upper glume apex obtuse, or acute.

Florets: basal sterile florets male; with palea. Lemma of lower sterile floret similar to upper glume; elliptic; 1 length of spikelet; membranous; 5-veined; obtuse, or acute. Fertile lemma elliptic; 1.2–2.4 mm long; indurate; dark brown; shiny; without keel; 5-veined. Lemma surface granulose; unwrinkled, or rugulose. Lemma margins involute. Lemma apex obtuse, or acute. Palea reflexed at apex; indurate.

Soil drainage

• impeded
• seasonally waterlogged

Soil reaction

• alkaline
• neutral

Soil texture

• heavy
• light
• medium

Special soil tolerances

• shallow

P. geminatum can spread by seed or by clones, using the latter particularly at disturbed sites. It is adept at colonizing compacted and denuded soils from stem pieces (Pouder et al., 2006). Fragments of both emergent and decumbent stems are inadvertently cut and buried by the digging, shifting and ploughing of engineering and maintenance machinery.

P. geminatum can spread through irrigation canals, open waste ditches and polluted riparian systems.

In all cases reviewed herein, problems caused by P. geminatum were apparently the result of environmental disturbances by human intervention rather than its introduction as an alien species. Indeed, P. geminatum is not on alert or regulated pest species lists. In Florida, USA, it is routinely protected during management practices and propagated on a large scale for habitat enhancement and lake restoration (see Environmental Services).

Competitive biological characteristics, such as monopolizing resources or shading associates (see Risk and Impact Factors Summary Table: Impact Outcomes), have not been demonstrated with P. geminatum.

By its rheophytic nature, P. geminatum has been recorded as contributing to the blockage of smaller streams in west Africa (Burkill, 1985). Its primary negative impact, however, occurs in arid and warm temperate zones, such as in Egypt, Pakistan and Mexico, where it can spread through irrigation canals, open waste ditches and polluted riparian systems. In these situations, extensive biomass produced can compromise water flow and flood control (Shaltout et al., 1995).

• Invasive in its native range
• Has a broad native range
• Abundant in its native range
• Highly adaptable to different environments
• Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
• Pioneering in disturbed areas
• Capable of securing and ingesting a wide range of food
• Highly mobile locally
• Benefits from human association (i.e. it is a human commensal)
• Long lived
• Fast growing
• Gregarious
• Has propagules that can remain viable for more than one year
• Reproduces asexually

• Increases vulnerability to invasions
• Monoculture formation
• Negatively impacts agriculture
• Soil accretion

• Filtration
• Rapid growth
• Rooting

Economic Value

Naturally occurring stands of P. geminatum are well recognized as useful wild pasture for livestock. As reported from Senegal, Nigeria, Somalia, Uganda, and India it is enjoyed by nearly all types of livestock, the succulent culms probably adding to its palatability (Burkill, 1985). The species has been noted as especially important before the start of the rainy season in the upper Ganges basin of India, after standing water has been replaced by low-lying meadows favoured for cattle and pig grazing (Misra, 1976). More recently in Sri Lanka, P. geminatum was highlighted, along with six other naturally occurring grass species, for its ability to maintain dominance under brackish marsh environments; it is therefore expected to become more important as rising sea levels and associated tides increase salinity farther inland (Premaratne and Premalal, 2008).

Social Benefit

P. geminatum is traditionally used by the Seminole Indians of southern Florida as a dermatological aid. A decoction of the whole plant was taken and used as a body steam for the skin problem ‘snake sickness’. It was also used as a remedy for itchy skin (Sturtevan, 1954, as cited in Moerman, 2013). This traditional Native American use may still be employed in the Everglades region today.

Burkill (1985) found no record of the seed of P. geminatum being collected for human use, although he speculated that its seed also may be edible. In India the seed of P. flavidum is collected as a famine food.

Environmental Services

P. geminatum functions as a primary coloniser of newly flooded lake beds, forming broad, emergent zones that quickly act as wave buffers and allow other species to establish, for example in Tanzania (Welsh and Denny, 1978) and Florida (Pouder et al., 2006).

P. geminatum can also create an offshore habitat for fish and aquatic fauna. Even in nutrient-enriched lake waters, P. geminatum maintains a more open benthic and littoral community with a type of structural complexity that supports and distributes periphyton and epiphytic macroinvertebrates vertically through the water column.

In areas of the Nyumba ya Mungu reservoir, Tanzania, that were dominated by P. geminatum, the occurrence of major shoals of commercial fishes (Sarotherodonpangani and S. jipe) correlated with their habit of feeding on periphytic algae (Bailey et al., 1978; Bowker and Denny, 1978). Studies in Florida revealed similar findings. In large lakes of central Florida, Schramm and Jirka (1989) found that the open, intermediate density of underwater stems produced by P. geminatum supported epiphyton at numbers and diversities that much exceeded those found with other aquatic plants. Welch (2009) also found P. geminatum to offer especially productive habitat for freshwater fish favoured by anglers in Lake Tohopekaliga, Florida.

Wildlife Food and Habitat

P. geminatum is grazed on by a variety of animals, including hippopotamus (Lock, 1973). Elephants have been observed freely grazing on the floating mat habitats created by P. geminatum along the lake margins of the upper Ganges (Misra, 1976).

Grasses and sedge marshes supported by P. geminatum provide the only known overwintering ground for the Siberian crane (Grus leucogeranus) on the Indian subcontinent, at Keoladeo Ghana Bird Sanctuary. The habitat supports an enormous avian fauna (Gopal, 1994).

Lake Restoration

In natural areas around the world, emergent stands of P. geminatum are highly desired for their use in ecosystem management. It is particularly well adapted to quick regrowth on land re-flooded after a dry period and is valued for controlling erosion and as an indicator of water quality (for example in Peru; Leon et al., 1977).

It has been employed routinely since 1976 to restore or improve degraded aquatic habitats in eutrophic lakes in Florida.

Restoration management entails two methods of propagation: 1) growing tips and stem fragments, and 2) whole plants. Stem regeneration should be consistently more successful at lower elevations where stems were buried closer to the water’s edge (Pouder et al., 2006). To collect stem fragments, cutting at a depth of 30 to 70 cm below the water surface was achieved with a mechanical aquatic harvester (Kelpin 800, 21.3 m harvester) (Mallison et al., 2006). Harvesting had a minimal, short term effect on offshore populations. Within three weeks, emergent regrowth of the source plants had advanced to equal that of pre-harvest densities (Mallison et al., 2006). Transplants or stem fragments are planted to a water depth of 2.5 m following herbicide treatment or drawdown and scouring for dirt removal (Mallison and Thompson, 2010).