T. latifolia is a cosmopolitan plant, occurring in wetlands through most temperature zones in North America, Europe and Asia, and many subtropical areas. It has also begun to invade the few regions where it is...
T. latifolia is a cosmopolitan plant, occurring in wetlands through most temperature zones in North America, Europe and Asia, and many subtropical areas. It has also begun to invade the few regions where it is not native, e.g., Oceania, South-East Asia and the Hawaiian islands. It forms dense populations under suitable conditions, often as monocultures excluding other species of vegetation. Holm et al. (1997) designated it as one of the “World’s Worst Weeds”. T. latifolia can reduce rice production, impact wildlife populations and can alter nutrient cycles negatively. In New Zealand it is classed as an “unwanted organism” as part of the National Plant Pest Accord (Champion et al., 2007). Potential for rapid clonal growth and long persistence of T. latifolia in areas where it is native presents a warning against establishment of this species in areas where it is not native and would impact native biodiversity.
Typha latifolia was named by Linnaeus in 1753. A significant hybrid is formed between T. latifolia and T. angustifolia: T. x glauca. Hybridization has been noted in Europe, but studied more recently in North America where there is still some question about the extent of T. x glauca (Zhang et al., 2008). There are numerous local common names in English and other languages, but broadleaf cattail seems to be the most widely used name in the literature.
T. latifolia is an erect thick-stemmed perennial with flowers consisting of cylindrical spikes, and stems 1-3 m tall. Linear, light green, flat leaves with a sheath at the base, extending to flowering spikes, 15-25 mm wide (Grace and Harris, 1986). Fibrous roots grow from rhizomes produced at base of leaves. Rhizomes are as long as 70 cm, 0.5-3 cm in diameter. Unisexual flowers include a pistillate portion below the staminate portion, forming a continuous spike 12-35 mm in diameter. Spike goes from green to brown as ripening occurs. Staminate flowers have hair-like bracteoles; bracteoles absent in pistillate flowers. Pollen grains formed in tetrads. Over 1000 flowers may be produced on one plant. Nutlike achenes about 1.5 mm long are derived from fertilized flowers. Seeds eventually break off generally by wind or water and are transported via long slender hairs (Hitchcock and Cronquist, 1973; Grace and Harrison, 1986; Welsh et al., 1987; Hickman, 1993; Larson, 1993; Pojar and MacKinnon, 1994).
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Aquatic Herbaceous Perennial Seed propagated Vegetatively propagated
T. latifolia is a cosmopolitan species, with its native range encompassing large regions on all continents, except Antarctica, Africa and Oceania. T. latifolia is known to occur in at least seven African countries (USDA-ARS, 2010). It is recorded as having been established as a non-native species in six countries (Australia, Indonesia, Malaysia, New Zealand, Papua New Guinea, the Philippines) and the USA state of Hawaii (Global Invasive Species Database, 2006). In New Zealand, it is not presently established but it has been found within the nursery/aquarium trade (Champion et al., 2007). T. latifolia is currently recorded as naturalized in low-lying wet areas on three of the Hawaiian islands: Kauai, Hawaii (the big island), Maui and Oahu (Wagner et al., 1999; HISP, 2008; PIER, 2009). Given the ability of T. latifolia to thrive in a broad array of temperature or semi-tropical habitats from the Arctic circle to 30°S latitude (Sculthorpe, 1967), T. latifolia may also be established on other oceanic islands with suitable wetland habitats (but not recorded). It is also increasingly seen as taking on invasive characteristics in some countries where it is native (Shih and Finkelstein, 2008; Olson et al., 2009). Furthermore, the hybrid product of T. latifolia and T. angustifolia, T. x glauca tends to be more invasive than T. latifolia (Olson et al., 2009).
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.
Details of how T. latifolia spread beyond its native range are difficult to ascertain, partly because there are so few regions in the world where it is not native. Furthermore, similarities between T. latifolia and native Typha species may have helped obscure invasions of new areas. Even in North America, where T. x glauca (hybrid of T. angustifolia and T. latifolia) has recently been seen to occupy a much larger distribution, the history of the spread of T. x glauca and the mechanisms involved have yet to be worked out (Shih and Finkelstein, 2008; Zhang et al., 2008).
A risk assessment was carried out for T. latifolia according to the Australian/New Zealand Weed Risk Assessment adapted for Hawaii (PIER, 2008). This identified T. latifolia having a high risk of invasion for the Pacific Islands, based on information from throughout the world on invasive features of T. latifolia such as high levels of seed production, persistence of seeds and rhizomes, and ability to form monocultures in wetland areas. There are few temperate or subtropical regions in the world where T. latifolia is not found, and therefore it would appear that this highly adaptable species is a threat to invade areas where it does not exist, especially if transported anthropogenically, either intentionally or accidentally.
T. latifolia grows in a wide variety of wetland habitats. Niches include marshes, wet meadows, lakeshores, roadside ditches, seacoast estuaries, pond margins, bogs or fens as well as rice paddies (Grace and Harrison, 1986). Salt tolerance is limited, but it does grow in marine wetlands with moderate salinity, and likewise can tolerate acidity (Hotchkiss and Dozier, 1949; Smith, 1967a,b; Hootsmans and Weigman, 1998). Communities occupied by T. latifolia range from early to late successional stages. Although it is a dominant species in many wetlands forming high densities, in other wetlands it occurs as scattered individuals or clumps. It also may occupy somewhat drier sites, such as along the edge of marshy woodlands or among woody shrubs (Grace and Wetzel, 1981a). It tends to prefer shallower water zones than T. angustifolia (Grace and Wetzel, 1981b). The only type of agricultural habitat where T. latifolia regularly occurs is in rice paddies (Mitich, 2001).
A chromosome number of 2n = 30 has been reported from North America and Europe (Roscoe, 1927; Darlington and Wylie, 1955; Goldblatt, 1981). A large amount of variation occurs in the morphology of T. latifolia through its cosmopolitan range. T. latifolia shows ecotypic variation (e.g. in photoperiod requirements) across latitudinal and altitudinal gradients (McNaughton, 1966), but this may be largely a phenotypic response (Tsyusko et al., 2005). Despite the relatively wide leaf blades of T. latifolia compared to other Typha species, there is considerable plasticity in the width of the leaves (Flora of North America Association, 2008). However, a general lack of genetic diversity has been reported in T. latifolia populations (Mashburn et al., 1978, Sharitz et al., 1980; Keane et al., 1999; Lamote et al., 2005) as would be expected by the predominant mode of reproduction being self-pollination and vegetative growth via rhizomes (Krattinger, 1975). However, somewhat higher genetic variation has been found utilizing microsatellite DNA markers (Tsyusko et al., 2005). Tsyusko et al. (2006) found greater variation in T. latifolia near the Chernobyl reactor in the Ukraine, but this was attributed to environmental factors rather than impact of the radiation from the Chernobyl nuclear accident in 1986.
Hybridization between T. latifolia and T. angustifolia to produce T. x glauca was first described by Kronfeld (1889) in Europe. T. angustifolia is the maternal parent of the hybrid (Kuehn et al., 1999). T. x glauca possesses characteristics intermediate between the two parent species and is considered a distinct species in North America (Grace and Harrison, 1986). This distinct nature of T. x glauca is reflected in electropohretic studies (Krattinger et al., 1979; Sharitz et al., 1980) and pollen morphology, which departs from the tetrads produced by T. latifolia (Gleason and Cronquist, 1963; Grace and Harrison, 1986). Pollen of T. x glauca is produced in a variety of forms including monads, diads, triads and tetrads and the plant is mostly sterile, with reproduction occurring primarily by vegetative means (Gleason and Cronquist, 1963; Smith, 1967a,b; Grace and Harrison, 1986; Larson, 1993). T. x glauca is relatively common in southeastern Canada and northern areas in the USA as well as California, and forms hybrid swarms with T. latifolia (Marsh, 1962; Smith, 1967a,b; Bayly and O’Neill, 1971). Hybrids have also been reported between T. latifolia and T. domingensis in North America, although more evidence is needed to confirm such hybridization as a regular occurrence (Zhang et al., 2008). The hybrids are sterile, but can spread via clonal growth (Flora of North America Association, 2008). Introgression between T. latifolia is likely to be uncommon because of hybrid sterility. The prominence of T. x glauca as an invasive species in parts of North America suggests widespread hybridization (Zhang et al., 2008), yet field studies have shown hybridization to be a relatively rare event, for example failing to occur over a 6 year period among co-occurring T. latifolia and T. angustolia (Selbo and Snow, 2004). Genetic analysis of T. latifolia and T. angustolia by Tsyusko et al. (2005) in the Ukraine showed no evidence of hybridization between species in that region.
T. latifolia is wind-pollinated with some selfing occurring due to overlap between staminate and pistillate flowering (Krattinger, 1975). The plant is protogynous with stigmas receptive 1-2 days prior to pollen release on a given plant (but stigmas remain receptive for four weeks) (Smith, 1967a,b; Grace and Harrison, 1986). Large amounts of pollen are produced in tetrads, at an estimated rate of 900 million per inflorescence (Krattinger, 1975).
Seed production per inflorescence is estimated at between 20,000 and 700,000 (Prunster, 1941; Marsh, 1962; Yeo, 1964). Under dry conditions, the pistillodia within the spike shrivel allowing release of fruits. Gynophore hairs on the fruits allow long-distance dispersal by wind under dry conditions. When a seed hits the water, the pericarp opens and releases the seed pointing downward which helps embed it in the mud or even in an organism that might further disperse it (Krattinger, 1975; Grace and Harrison, 1986).
Seeds may germinate immediately after release, but only under optimum conditions, including sufficient moisture (Leck and Graveline, 1979), warm enough temperatures (Morinaga, 1926) and relatively high light levels (Sharma and Gopal, 1979). Bonnewell et al. (1983) concluded that T. latifolia seed germination required high temperatures, low O2 concentration, and relatively long exposure to light to induce high percentages of seed germination. A greater percentage of seeds germinated at 35°C than at lower temperatures. Less than 10% of the seeds germinated at 15°C and none at 10°C. For submerged seeds exposed to red light (R), maximum germination was achieved when the O2 concentration in the water reduced to between 2.3 and 4.3 mg/litre at 30 °C. Under suboptimal conditions, seeds remain dormant for long periods (van der Valk and Davis, 1976; Keddy and Reznicek, 1986) and may form a large portion of the seed bank in wetland substrates, e.g. 25% (Leck and Graveline, 1979). Field-collected broadleaf cattail seed germinated after being stored in a freshwater canal in Washington State for 5 years (Comes et al., 1978). Optimal conditions for seed germination also promote seedling establishment. Variations in water level can have critical impacts on population dynamics of T. latifolia (Keddy, 1982; Keddy and Reznicek, 1986).
Plants growing from seed may reach flowering size in the first season. Clonal growth is prolific, with new stalks sprouting from underground rhizomes. The rhizomes are the longest-lived organs, often woody, and potentially remaining viable as long as 17-22 months (Westlake, 1968). As a result, they make up more than half the total plant biomass in a given stand (Westlake, 1965; 1982).
Physiology and Phenology
In general, leaves are produced in the spring, flowering occurs in early to mid-summer, and major clonal growth in the autumn with some variation across latitudes (McNaughton, 1966; Grace and Harrison, 1986; Motivans and Apfelbaum, 1987). In an established stand of T. latifolia in Michigan, USA, Dickerman and Wetzel (1985) observed three pulses of shoot emergence from rhizomes. The first emerged in early spring, grew over the summer, and senesced in autumn. The second pulse was in mid-summer, and about three-quarters of the shoots senesced in the autumn, and the remainder began growing again in the following spring. The final pulse emerged in late summer and the majority of shoots resumed growth in the final year.
After germination, 2-4 small leaves are produced and 2-6 floating leaves prior to production of erect leaves. Rhizome growth begins after shoots are 35-45 cm tall (Holm et al., 1997). When flowering occurs, leaf growth ceases as the meristem is consumed. The principle meristem of the ramet is basal, giving rise to both flowers and leaves. Flowering terminates the life of the ramet, while clonal growth may simultaneously lead to expansion of the population, e.g., as large as 54 m2 in 2 years subsequent to germination with a total rhizome length of 480 m (Holm et al., 1997).
Rhizomes are very resilient and often woody and up to 10 cm in diameter, usually occurring just below the soil surface (Great Plains Flora Association, 1986). Under some environmental conditions they occur at somewhat greater depths, such as an alluvial basin in central Iowa where rhizomes were 15-20 cm below the surface (Hayden, 1919).
The architecture and life history of T. latifolia is better adapted to shallower water in comparison to T. angustifolia, and because T. latifolia is a superior competitor, T. angustifolia generally occupies deeper water zones where the two species co-occur (Grace and Wetzel, 1981a,b; Grace, 1985).
Photosynthetic rates are relatively high in T. latifolia, and enable this species to be among the most rapid growing of all plants, surpassing production rates for crops like maize and sorghum (McNaughton, 1973; Dickerman and Wetzel, 1985; Motivans and Apfelbaum, 1987). The vertical leaves expose a maximum leaf surface while minimizing self- shading (Dykyjova, 1971a,b). The input of energy early in the seasons from rhizomes also enables the plant to maximize its photosynthesis at optimal times for utilizing available solar energy (Dickerman and Wetzel, 1985).
T. latifolia is capable of thriving even under anaerobic conditions, partly by way of aerating roots and rhizomes (Sale and Wetzel, 1983). T. latifolia also has nitrogen fixation capability, measured in one study as 18 kg N per ha per year or 8.2% of the N present in the standing biomass of T. latifolia (Biesboer, 1984).
T. latifolia frequently forms monospecific stands via clonal growth that produces a dense ramet population, and thus frequently very few other vascular plants are associated with broadleaf cattail. Bacteria associated with the rhizosphere aid in nitrogen fixation by T. latifolia (Biesboer, 1984).
As an emergent aquatic plant, dominance of T. latifolia in aquatic ecosystems tends to follow early primary succession stages featuring submerged leaf and floating leaf species (Gucker, 2008). In some situations, T. latifolia colonizes habitats as a pioneer species, e.g. mudflows from the eruption of Mount St. Helens (Halpern and Harmon, 1983). In terms of secondary succession T. latifolia rapidly colonizes areas of recent disturbance where openings have been created, such as bogs disturbed by fire (Gates, 1942).
T. latifolia also tends to colonize undisturbed sites (Grace and Harrison, 1986), but is vulnerable to competition from other wetland species that tend to be more invasive such as Lythrum salicaria (purple loosestrife) or Phragmites australis (common reed) (Hager, 2004; McGlynn, 2009).
Preferred habitats include slightly brackish marshes and a variety of freshwater systems with slow-moving water. T. latifolia occupies wetlands over a broad spectrum of climates including tropical, subtropical, southern and northern temperate, humid coastal and dry continental climates (Grace and Harrison, 1986). In areas near the Arctic Circle such as Alaska, T. latifolia populations persist despite winter temperatures as low as - 34°C, and conditions whereby bodies of water are frozen from September to May (Grace and Harrison, 1986). At the other extreme, T. latifolia populations can persist in warm desert habitats such as Arizona sites which receive rainfall of less than 100 mm (McDonald and Hughes, 1968). T. latifolia can also exist in warm climates with high levels of humidity and plentiful summer rainfall, such as the Everglades region in southern Florida (Long, 1974).
In terms of elevation, T. latifolia also occupies a broad range, found as high as 2,300 m in parts of North America and also occupying many locations at sea level (Flora of North America Association, 2008).
T. latifolia grows in a variety of soil types. Soil textures associated with T. latifolia range through sandy, silty, loam or clay (Gucker, 2008). T. latifolia found in oxbow lakes in Alberta tolerated soils with a pH of up to 9.2 (Liefers, 1983), in contrast to boggy sites where T. latifolia has been observed to grow in areas with a pH as low as 3.4-3.5 (Schuurkes et al., 1986; Wieder et al., 1990). However, a study by Brix et al. (2002) found that growth of T. latifolia in a hydroponic environment stopped at pH 3.5, likely due to impacts on plasma membrane, and the authors concluded that the ability of T. latifolia to occupy low pH was through modification of the rhizosphere environment to protect tissues from high acidity. Excess nutrients or eutrophication of a wetland may cause T. latifolia to increase at the expense of other wetland plant species (Drohan et al., 2006).
In some areas, T. latifolia can survive with very minimal soil, when it forms floating mats in wetlands. Air spaces in the rhizomes provide buoyancy for smaller mats, while thicker mats are buoyed up by air bubbles produced during anaerobic decomposition (Hogg and Wein, 1988).
Salinity tolerance is stage-dependent with no seeds germinating above 1 atm osmotic pressure, but T. latifolia exhibits more tolerance in the seedling stage and older (Choudhuri, 1968). In Louisiana, USA, T. latifolia grows in areas with salinity levels up to 1.13% (Penfound and Hathaway, 1938); T. latifolia was found to exist in environments with less than 10 mS/cm salinity in western Canada (Shay and Shay, 1986).
Flooding and water depth are key determinants of the establishment and persistence of T. latifolia populations. Tolerance of fluctuating water levels depends on a variety of factors, including the maturity of plants, rhizome production, associated vegetation and other disturbances (Grace, 1989; Gucker, 2008). As an emergent plant, optimal water levels tend to be high enough to keep lower parts of the plants submerged, but low enough to prevent interference with photosynthesis and respiration. Controlled experiments showed decreased rhizome production at water levels above 30 cm (Weller, 1975). T. latifolia died in water depths over 95 cm and density was greatest at 22 cm depths in experimental ponds in Arkansas (Grace, 1989). Oxygen is transported from aerial portions to rhizomes to allow survival and growth so long as enough of the plant is above water (Sale and Wetzel, 1983). T. latifolia has been found to tolerate drying of wetlands over several months (Fickbohm and Zhu, 2006), but perish if water was drained for a period of 2 years (Nelson and Dietz, 1966).
The apple snail (Pomacea insularum), native to South America, was observed feeding on T. latifolia in North America (Burlakova et al., 2009).
Numerous fungi have been identified on T. latifolia, colonizing various stages of the plant. Shulz and Thorman (2005) identified 45 species on T. latifolia from northern Alberta alone.
Various terrestrial birds may use the cattail fruits for nesting materials; stems are utilized by aquatic birds for nesting material and cover (Motivans and Afelbaum, 1987). Some ducks feed on the seeds, although the seeds are too small to be a valued food source; geese consume the stems (USDA-NRCS, 2010).
Muskrats have significant impacts on the ecology of T. latifolia, with T. latifolia (particularly stems and roots) forming a major food source for these rodents; muskrats also utilize the stems for housing materials (Motivans and Afelbaum, 1987; USDA-NRCS, 2010). Other small mammals such as white-footed mice and nutria have also been found to utilize T. latifolia (Nickell, 1965; Kinler et al., 1987).
Various ungulates have been found to graze on T. latifolia including livestock (e.g. cattle) as well as wild ungulates, e.g. deer, elk or moose (Boggs et al., 1990; USDA-ARS, 2010).
Seeds of T. latifolia may be transported on a large scale by wind or by water, and are well-adapted for these modes of dispersal (Grace and Harrison, 1986). The plumed seeds may have a potential wind-dispersal range of 3600 m (Soons and Ozinga, 2005). Rhizome growth and fragmentation may also provide a mechanism for short-distance dispersal (Grace and Wetzel, 1981a). Even within its native range, T. latifolia has been observed to increase; in North America various Typha species have undergone range expansion, particularly T. angustifolia and T. x glauca, as a result of anthropogenically influenced environmental stressors allowing T. x glauca to occupy areas beyond the traditional range of T. latifolia (Waters and Shay, 1990; 1992; Galatowitch et al., 1999).
Vector Transmission (Biotic)
Seeds may be readily transported by birds and livestock through their presence in mud in areas where T. latifolia grows (DPIWE, 2005), and disturbance by animals may also play a role (Hewitt and Miyanishi, 1997).
Mud transported with machinery may carry large numbers of T. latifolia seed (DPIWE, 2005). The frequent occurrence of T. latifolia in damp roadside areas facilitates dispersal along corridors created by roadways (Hansen and Clevenger, 2005).
T. latifolia is more commonly referred to as a weed in Europe and North America than in other regions in its native range. T. latifolia infests irrigated systems and aquacultural systems, e.g. in Australia, India, and Romania, and is a problem affecting irrigated rice in Morocco and Russia. It is a common rice weed in USA (Oryza sativa) and also occurs in rice in Greece, India, Iran, Mexico, the Philippines, and Portugal (Mitich, 2001). A California survey found 47% of rice fields contained T. latifolia (McIntyre and Barrett, 1985). In Hawaii, establishment of T. latifolia threatens production of taro (HISP, 2008).
Excessive populations of T. latifolia may invade canals, ditches, reservoirs, cultivated fields, and farm ponds; it may impact recreational lakes negatively and reduce biodiversity and displace species more desirable for certain kinds of wildlife (Morton, 1975; Grace and Harrison, 1986; Thieret and Luken, 1996).
The ability of T. latifolia to dominate wetlands on a large scale, and rapidly create large amounts of biomass enables these plants to play major roles in nutrient cycles. A wetland without Typha invaded by T. glauca exhibited large changes in the sediment characteristics, including ten times as much soluble ammonium, nitrate and phosphate, indicating the wetland was unable to remove nutrients effectively (Angeloni et al., 2006). A key to understanding many wetland systems with large populations of T. latifolia is the dynamics of the litter produced through the lifecycle of this highly productive plant that goes through repeated cycles of re-birth and decay (Farrer and Goldberg, 2009). Establishment or expansion of T. latifolia populations may also greatly influence fire dynamics (Gucker, 2008).
Impact on Biodiversity
In Hawaii, wetlands are home to rare endemic birds such as the Hawaiian stilt (Himantopus himantopus knudseni) and the Hawaiin duck or koloa maoli (Anas wyvilliana) which are threatened by infestations of T. latifolia (HISP, 2008). Likewise, there are vulnerable indigenous wetland species in other geographic regions being invaded by T. latifolia such as New Zealand, Australia and parts of Southeast Asia. The ability of T. latifolia to quickly spread once it is introduced to an area is augmented by the potential seen in recent years for hybridization with other Typha species (Galatowitsch et al., 1999), although more work needs to be carried out to understand the nature of such hybridization (Shih and Finkelstein, 2008; Zhang et al., 2008).
T. latifolia is a well-known plant to many people around the world, and often an indicator of healthy wetlands, which are increasingly recognized as providing significant ecosystem services in the global environment. However, in contexts where T. latifolia negatively impacts the environment, particularly wildlife, a negative social impact results as well (Motivans and Apfelbaum, 1987; HISP, 2008).
T. latifolia and other Typha species were historically used by many indigenous peoples (Turner, 1981; Gott, 1999). Various parts of the plant may be eaten, e.g. rhizomes as a cooked vegetable or as a source of flour; pollen also in the genesis of flour; shoots may be eaten raw or cooked; spikes may be eaten raw, boiled or used as soup stock (Fernald et al., 1958; Turner, 1981).
Historically T. latifolia has been used throughout the world as building material, bedding, basketry, shoemaking, rope and paper manufacture and within a variety of herbal applications (Ramey, 1981; Mitich, 2001). Fluff from fruiting spikes has been employed as tinder and insulation, dressing burns, and stuffing pillows, mattresses and various other articles. Still today Typha species are seen as having a large unrealized potential, and new uses are envisioned, such as biomass production or as a modern-day food crop (Morton, 1975; Pratt et al., 1980; Ciria et al., 2005). Other relatively new uses include water purification, bioremediation (Carranza-Alvarez et al., 2008; Chun and Choi, 2009; Moore et al., 2009), as a bioindicator of pollution (Mirka et al., 1996) or the production of chemical products (Staba, 1973). A recent investigation looked at the potential of T. latifolia to bioremediate naphthenic acids produced in extraction of petroleum from Alberta’s tar sands (Headley et al., 2009).
T. latifolia is cultivated as an ornamental. It is often sold commercially and planted for wildlife habitat and in wetland restoration.
The environments created by T. latifolia frequently hold great importance in terms of recreational value, and are highly prized by outdoor enthusiasts including hunters, fishermen, and naturalists.
The value of T. latifolia and its congeners to a variety of wildlife has been well documented (Grace and Harrison, 1986). Certain types of wildlife such as red-winged blackbirds and muskrats in North America have a very close association with cattail marshes (Skinner and Skinner, 2008). T. latifolia also can be an indicator of the nutrient balance of a given system, as well as an agent to promote balance through nutrient cycling (Craft, 2007). T. latifolia grew more rapidly in response to increased carbon dioxide, which may indicate some potential for the maintenance of T. latifolia populations to ameliorate climate change, depending on the litter dynamics in a given system (Sullivan et al., 2010).
A survey was conducted among people in the aquatic plant trade in New Zealand (Champion and Clayton, 2001), and in the process provided information on identification so that T. latifolia could be distinguished from the native Typha species, T. orientalis (Champion et al., 2007). In particular,characteristics used to distinguish T. latifolia were: leaf sheaths tapering to lamina, female flower lacking scales, female spike dark brown, male and female spikes of similar lengths, and the grouping of pollen grains in tetrads. The identification utilized literature resources such as Fassett and Calhoun (1952), Aston (1973), Tutin et al. (1980), and Smith (1967a,b). The two species as well as T. laxmannii, another potential invader of New Zealand, are illustrated in Champion et al. (2007).
Key characteristics distinguishing T. latifolia from T. angustifolia and the hybrid T. x glauca are: leaves which rarely overtop the flowering spike and broader leaves (5-19 mm wide in T. x glauca and moderately planoconvex and 3-8 mm wide in T. angustifolia and strongly planoconvex), usually contiguous staminate and pistillate spikes (separated by a gap of 5-120 mm in T. angustifolia and 0-33 mm in T. x glauca), and a robust, dark brown spike at maturity with no pistillate bracheoles (T. angustifolia and T. x glauca have pistillate bracheoles and the pistillate spike is green for T. x glauca at antithesis) (Grace and Harrison, 1986).
There are challenges to distinguishing T. domingensis and T. latifolia in the field because of morphological similarities, particularly before the flower appears. T. latifolia may often be identified by darker pistillate flowers and wider leaves, but a gap between the staminate and pistillate is considered the defining characteristic of T. domingensis, though such characteristics are not always consistent (Zhang et al., 2008).
By comparison to T. orientalis (raupo) (native to New Zealand and Australia), the leaves of T. latifolia are broader, flatter and paler, and the flower spark is black-brown in colour compared with the chestnut brown of T. orientalis (Champion et al., 2007).
T. latifolia is banned from sale, propagation and distribution throughout New Zealand (MAF Biosecurity Authority, 2002; Champion et al., 2007). Similar restrictions are in place in other areas where it is an alien invasive, although evidently T. latifolia is still available for sale in places such as Australia (where it appears for sale on horticultural websites).
Within some areas of its introduced range where populations are relatively sparse (e.g. New Zealand or Hawaii), attempts are being made to eradicate T. latifolia through removal of all plants and rhizomes where it appears, or through employing other methods of control (Champion et al., 2007; HISP, 2008).
Cultural control and sanitary measures
Frequently T. latifolia is not seen as a weed to be eradicated, but rather a plant that must be managed to prevent populations from reaching damaging levels. Cultural control methods may often be key in managing populations at acceptable levels. Three common goals in T. latifolia management, as listed by Motivans and Apfelbaum (1987) are to:
1.Ensure that spread of T. latifolia does not lead to domination of native habitats;
2.Avoid the reduction of native plant populations due to proliferation of T. latifolia;
3.Prevent formation of large monocultures of T. latifolia and associated loss of habitat diversity.
Water level modification serves as a major cultural tool to manage populations of T. latifolia and other Typha species. Either flooding or draining of wetlands is likely to reduce populations, but these techniques must be used judiciously to avoid negative side effects. Seeds may disperse to a site, or germinate from seed banks rapidly following a flooding event; likewise, rhizomes can produce new plants readily (Motivans and Apfelbaum, 1987). If water levels increase enough to submerge large portions of the above-ground plant (e.g. 65 cm or greater), there can be significant impacts. Likewise draining can reduce vigour of T. latifolia plants and population decline, but often only after one or two years of low water levels, and if accompanied by burning may have much greater efficacy (Motivans and Apfelbaum, 1987). By drawing down water levels, reductions in T. latifolia may allow annual species preferred by waterfowl to establish (Kadlec and Wentz, 1974).
Fire and physical removal (cutting) can be used to control T. latifolia, and is particularly effective when accompanied by manipulating water level (Motivans and Apfelbaun, 1987). Fire also reduces litter and contributes to better access for further mechanical measures (Malik and Wein, 1986).
One effective method of physical control involves cutting stems followed by submergence of the stems that remain (Gucker, 2008). Sale and Wetzel (1983) found that if relatively small fractions of T. latifolia or T. angustifolia stems remained above water after cutting, the plants were able to survive. However, complete submergence seriously compromised the physiology of rhizomes via anaerobic respiration. Clipping may be repeated for increased efficacy. Black polyethylene tarps may also be employed to kill T. latifolia through solarization. Small seedlings can also be uprooted, but care must be taken to remove all traces of rhizomes (DPIWE, 2005).
Because of the long-dispersal capability of T. latifolia seeds, the plant may readily re-establish in areas where it has been controlled, so long as there are seed sources within a 1 km radius or greater. However, attempts can be made to prevent movement of seeds through presence of mud from T. latifolia wetlands on machinery.
Although a number of insects and fungi are documented as feeding on T. latifolia and other Typha species, biological control as an option for managing cattails has not been explored. However, grazing by ungulates has been shown to help reduce stand densities (Gucker, 2008), although aquatic animals such as muskrats or geese (Canada geese or snow geese) may often be more effective (Sojda and Solberg, 1993). Population levels of 10 muskrats/acre were found to nearly eliminate cattails in 2 years when combined with high spring water levels (Sojda and Solberg, 1993).
Soil applied herbicides are generally ineffective in controlling T. latifolia, so long as standing water is present (Sculthorpe, 1967; Grace and Harrison, 1987). A number of foliar applied herbicides have been demonstrated to control T. latifolia, including 2, 4-D, amitrole, dalapon and paraquat (Corns and Gupta, 1971). Repeated herbicide applications are often necessary, e.g. up to 3 years (Apfelbaum, 1985).
In Queensland, Australia, where T. latifolia is not native, different herbicides are recommended for different situations (DPI Queensland 2007). For waterways, channels and drains, either glyphosate or 2, 2-DPA systemic herbicide is recommended. Likewise glyphosate is recommended for bore drains or pastures, whereas spot spraying amitrole is recommended for irrigation channels.
Particularly where the nearly cosmopolitan T. latifolia is native, eradication is seldom the goal, but rather achieving ideal population levels. For wildlife management purposes, a 50:50 cover:water ratio may be optimal in many habitats (Beule, 1979), and managers may be able to achieve this largely through water level management. Likewise, where T. latifolia is non-native, it may be nearly impossible to eradicate it, but cultural management techniques may be employed to reduce populations.
T. latifolia has frequently been planted and/or managed to provide ecosystem services in wetlands to promote wildlife habitat, stabilize shorelines or reduce contaminants or even salinity (Marsh, 1962; Gopal and Sharma, 1980; Bonham, 1983).
There is a need for further research on management, particularly in areas where it is not-native. Almost no work has been done to examine the potential for biological control. There is also a great need for more work to look at specific impacts T. latifolia has on biodiversity on all levels.