Curlyleaf pondweed (Potamogeton crispus L.)
Angela Poovey
FISH 423
Fall 2008 1. Diagnostic information Basic identification key Class Liliopsida – Monocotyledons Curlyleaf pondweed (Potamogeton Subclass Alismatidae crispus L.) is a rooted submersed macrophyte that grows in freshwater lakes, ponds, rivers, and Order Najadales streams. It may be found in slightly brackish Family Potamogetonaceae – waters (Catling and Dobson 1985). It grows Pondweed family entirely underwater except for the flower stalk Genus Potamogeton – pondweed which rises above the water (WA-DOE 2001). Species crispus – curlyleaf Although most pondweeds exhibit plasticity, in pondweed which the appearance of the same species may vary depending on growing conditions, curlyleaf Common names pondweed is easily identified. It has olive-green curlyleaf pondweed, curly-leaved pondweed, to reddish-brown leaves (Figure 1). Leaves are curly pondweed, crisp pondweed, or curly attached to narrow slightly flattened stems in an muckweed alternate pattern. They are oblong (3-8 cm long,
Figure 1. A stand of mature curlyleaf pondweed plants (left) and a plant stem (upper right). Note reddish-brown tinge with red midvein. Leaves have wavy edges and fine serrations (lower right). 5-12 mm wide) with margins that are distinctly Life-history and basic ecology wavy and finely serrated creating an overall leaf texture that is “crispy” (Borman et al. 1997). The cool water adaptations of curlyleaf Stems are branched and somewhat flattened; pondweed set it apart from other aquatic plants. they grow up to 90 cm (WA-DOE 2001). It survives as an entire plant under the ice Curlyleaf pondweed may be confused with (Wehrmeister and Stuckey 1992) while most Richardson’s pondweed (P. richardsonii, also plants are dormant as seeds or tubers, and dies called clasping leaf pondweed). Richardson’s back in mid-July while other plants are just pondweed has longer and wider leaves (3-10 cm reaching peak growth. The only component of long, 1-3 cm wide) with clasping leaf bases that the plant that “oversummers” are seeds and cause the leaf to curve backwards (Figure 2). vegetative turions. Leaves are smooth, distinctly green, lance- The seasonality of curlyleaf pondweed shaped, with white bands that are densely phenology (Figure 3) is triggered by changes in arranged around stem (WA-DOE 2001). photoperiod and water temperature (Bolduan et al. 1994). Turions break dormancy and sprout when summer water temperatures decrease to <20°C and day lengths shorten to 11 h (Kunii 1982). In the northern US, turion sprouting and plant growth generally occurs in September and October followed by little or no growth during the winter. During the winter, curlyleaf pondweed has relatively narrow leaves, which are limp, flat along the edges and blue-green in color (Wehrmeister and Stuckey 1992).
After ice out, when water temperatures rise to
10°C (Tobiessen and Snow 1984), shoots
rapidly elongate, detach from the turion, and
form roots. Leaves turn reddish-brown and
become wavy (Figure 1). Peak biomass occurs
late spring to early summer and coincides with
flowering and turion formation (Woolf and
Madsen 2003)
Curlyleaf pondweed produces small flowers that Figure 2. A colony of Richardson’s pondweed (left) and a plant stem (right). Note green color with white are arranged in terminal spikes (1-3 cm long) on midvein. Leaves have wavy edges, but are smooth. (Bolduan et al. 1994); however, recent research in an Oregon lake shows that turion formation may occur at water temperatures >12°C (Wells
Summer and Sytsma 2006). Curlyleaf pondweed produces two types: “stout, horny, denticulate” Fall turions and “slender spicular” turions Spring
Winter (terminology after Kunii 1989). Upon maturity, turions separate from the stem and sink to the sediment. Turion production typically lasts for two to three
Figure 3. A schematic months, peaking in June (Woolf and Madsen
of the curlyleaf 2003). Turion densities in a Minnesota lake pondweed life cycle ranged from 726 to 2,713 turions m-2 (Woolf and (after Wehrmeister and Madsen 2003), which corresponds to turion Stuckey 1992; top) and densities found in lakes and rivers throughout photo of a sprouting the world (Bolduan et al. 1994). Significantly turion (left image). lower turion densities were found in an Oregon
lake (3.9 turions m-2; Wells and Sytsma 2006). a curved stalk (2-7 cm) above the water surface (Figure 4). Fruits are 4-6 mm long and have three ridges with a conical beak (2-2.5 mm long). Seeds play a relatively minor role in reproduction (Catling and Dobson 1985, Bolduan et al. 1994). Persistence of curlyleaf pondweed depends on turions. Turions are large dormant apices consisting of numerous lobes that formed at both the ends and in the axils of stems (Figure 5). Clos (1856) Figure 4. A stand of first described curlyleaf turions as “unique curlyleaf pondweed among organs of vegetative reproduction in their plants that are horny consistency” (cited in Arber 1920). It is flowering (left) and generally accepted that turions form at water a plant stem with temperatures >15°C and day lengths >12 h fruits (right). is also found in sandy and hard-bottom sediments (Kunii 1989, Nichols 1992). Nichols (1999b) reports that curlyleaf pondweed grows in many Wisconsin lakes with broad ranges of conductivity (10-670 umhos/cm, mean 297) and alkalinity (10-260 mg/L CaCO3, mean
Photo by S. Wells Photo by S. Wells 142) and a moderate pH (6.5-9.9, mean 8.1). Although it may be an indicator of Figure 5. Photo of eutrophication (Nichols and Shaw 1986) and is denticulate (left best suited to nutrient-rich water, curlyleaf image) and spicular pondweed can be found in mesotrophic lakes (middle image) and streams (Nichols 1999a). turions. Photo of Curlyleaf pondweed tolerates low light turion formation in (Tobiessen and Snow 1984) and turbidity the axil of a leaf (Nichols 1992). Turbid-tolerant plants are those Photo by F. Koshere base (right image). species that bolt to the water surface from
energy stored from vegetative propagules right During turion production, roots have been found after ice-out before water clarity declines with to degenerate several weeks prior to senescence, increasing turbidity (Engel and Nichols 1994). causing the plants to separate from the bottom These species usually have complex root and form large floating mats on the lake surface systems to withstand wind-driven waves that (Woolf and Madsen 2003). After turion scour the lake bottom suspending sediments in production, senescence occurs as water the water column (Engel and Nichols 1994). temperatures increase (Wehrmeister and Stuckey The ability to grow at low temperatures gives 1992) and summer dormancy follows. curlyleaf pondweed a competitive advantage
over other native Potamogeton species. Environmental optima and tolerances Curlyleaf pondweed survives in water Curlyleaf pondweed can tolerate a wide temperatures of 1 to 4°C under ice and grows range of conditions. It is most often found rapidly when water temperatures reach 10 to growing in water depths of 1 to 3 m (Bolduan et 15°C (Tobiessen and Snow 1984). al. 1994), but can survive depths of 7 m
(Tobiessen and Snow 1984). It occurs in both Biotic associations lentic and lotic systems. Curlyleaf pondweed Curlyleaf pondweed can exist with to by S. Wells grows best in soft organic sediments; however, it native plants without dominating. In those areas, common submersed associates of curlyleaf pondweed are coontail (Ceratophyllum demersum), Canadian waterweed (Elodea canadensis), leafy pondweed (P. foliosus), and flat-stem pondweed (P. zosteriformis). Emergent plants growing near curlyleaf pondweed stands are arrowhead (Sagittaria latifolia) and cattail (Typha latifolia) as well as small free-floating duckweeds (Lemna minor, L. Figure 6. Distribution of curlyleaf pondweed in the US. Areas in red indicate more abundant populations compared to areas in pink. Source: triscula) and watermeal (Wolffia Nonindigenous Aquatic Species Database (http://nas.er.usgs.gov). columbiana; Nichols and
Yandell 1995). Current geographic distribution Eurasian watermilfoil (Myriophyllum spicatum), another invasive aquatic plant often occurs with Curlyleaf pondweed is found in all 48 curlyleaf pondweed (Catling and Dobson 1985, states of the continental US (Figure 6). Nichols and Shaw 1986). Both curlyleaf In Oregon, curlyleaf pondweed occupies areas pondweed and Eurasian watermilfoil have along the Rogue River watershed, the contributed to the invasional meltdown of the Willamette River valley, the Columbia River Great Lakes (Ricciardi 2001). Mutualistic basin. interactions with zebra mussel (Dreissena In Washington, curlyleaf pondweed found polymorpha) and commensual interactions with around Puget Sound, along the Columbia, Snake the Asian bryozoan Lophopodella carteri have River, and Yakima River valleys. It also occurs been recorded; however, negative impacts on in the Pend Oreille River. Curlyleaf pondweed curlyleaf pondweed have also been identified is listed as a Class C noxious weed in with the parasitic aquatic moth Acentropus Washington. Class C noxious weeds are either niveus and common carp (Cyprinus carpio). already widespread in the state or are of special
interest to the agricultural industry. The Class C
status allows a county to enforce control if it is beneficial to that county while other counties Pathways, vectors and routes of introduction may choose to provide education or technical Stuckey (1979) proposed that long support for the removal or control of these distance dispersal of curlyleaf pondweed was weeds. primarily due to its presence in water with fish In Idaho, curlyleaf pondweed occurs in the St. and fish eggs that were transported to hatcheries Joe and Snake River valleys, Lake Pend Oreille, (Figure 8). This mode of dispersal is more Bonner County, and Priest watershed. In Idaho, likely than spread by migrating waterfowl that it is considered a high priority nonindigenous have eaten plant stems and turions (Stuckey species that is present in the state. 1979). Regional spread is probably caused by plant fragments attached to boats and boat History of Invasiveness trailers. Downstream transport of floating plant fragments and turions or movement of these Native to Eurasia, Africa and Australia, plant parts to another part of a lake via water curlyleaf pondweed was introduced into the US currents is most likely responsible for localized in the mid-1800s (Stuckey 1979). The earliest spread. collection of the plant was recorded in 1841- 1842 in Philadelphia with distribution limited to Factors influencing establishment and spread the northeastern portion of the US and a small Curlyleaf pondweed most readily portion of California prior to 1900 (Figure 7). establishes in nutrient rich impoundments and By 1930, it had spread westward to several other large shallow lakes that receive large states of the Great Lakes region. Spread to the fluxes of nutrient input (Nichols 1999a). southeastern US predominately occurred during Although distribution is initially patchy, the 1940s. Spread along the Pacific coast also colonies become uniform and widespread. occurred in the 1940s. Curlyleaf pondweed Lakes with high recreational activity (motorboat appeared in the lower Rogue River, Curry traffic), public access sites, with a history of County, Oregon in 1947. In the same year, it disturbance are most vulnerable to colonization was found in Washington, in a stream outlet of by curlyleaf pondweed. Native plant removal Long Lake, Thurston County, and two years also contributes to establishment of curlyleaf later, it was identified in Steilacoom Lake, pondweed (Nichols 1999a). Pierce County. The first report of curlyleaf pondweed in Idaho was in the St. Joe and Snake Potential ecological and/or economic impacts Rivers in 1973. By 1978, curlyleaf pondweed Curlyleaf pondweed is considered one encompassed most of the US and the lower of the worst submersed weeds in the West provinces of Canada. Figure 7. Distribution of curlyleaf pondweed pre-1900 (gray circles) and new infestations found 1900-1950 (blue circles). Distribution based on Stuckey (1979).
Figure 8. Spread of curlyleaf pondweed through fish hatchery activity from 1900-1975. Circles indicate sites where plants were found near hatcheries (from Stuckey 1979). (Parsons 2006). Currently, it is locally oxygen levels (anoxia), enhance release of problematic; however, there is concern that it nutrients, and produce strong vertical gradients will become more aggressive and cause in pH and temperature in the water column; all problems as it has in the Midwest. Its unique of which may stress aquatic organisms. life cycle allows curlyleaf pondweed to preempt Senescence of curlyleaf pondweed in mid- native plants in the early spring. Consequently, summer may cause filamentous algal blooms. curlyleaf pondweed can form dense monotypic Rooted aquatic plants like curlyleaf pondweed stands. These thick mats of vegetation can are nutrient pumps that take up nitrogen and interfere with navigation, clog water intakes, phosphorus in the sediment and release them in block boat docks, and infest swim beaches. the water column upon senescence (James et al. Potential economic impacts include loss of 2003). Nuisance algal species present in the revenue for recreational areas, loss of power water column exploit the new flux of nutrients generation, impeded water supply, and costs of and form unsightly blooms. Like thick mats of control. aquatic macrophytes, thick mats of filamentous Ecologically, monotypic stands alter habitat algae negatively impact water quality. complexity and heterogeneity resulting in changes in flora and fauna relationships. Management strategies and control methods Curlyleaf pondweed mats shade out native plants, reducing diversity and abundance Bouldan et al. (1994) claim that (Tobiessen et al. 1992). Different architecture curlyleaf pondweed may be more difficult to types of a diverse native aquatic plant control than Eurasian watermilfoil. Different community enhance the use of these plants by control strategies are employed for pioneer (1 to organisms for food and cover (Cheruvelil et al. 5 acres or 0.4 to 2 hectares; Table 1) and larger 2002). Higher macroinvertebrate diversity is infestations (Table 2). Madsen (2000) associated with native plant communities than thoroughly described the advantages and with plant communities dominated by disadvantages of physical, mechanical, nonindigenous species (reviewed in Nichols and biological, and chemical management Shaw 1986). Aquatic plant communities serve techniques; his descriptions are used here. as food resources, refugia from predators and Often, management techniques are applied when nursery habitats for fish. Increased numbers and curlyleaf pondweed becomes a nuisance in late diversity of fish species has been correlated with spring or early summer after turion formation. higher aquatic plant richness and abundance While many control methods greatly reduce (Weaver et al. 1997). As plants dominate the seasonal plant biomass, they have been water column, they contribute to low dissolved ineffective at reducing turion numbers and months) than previously published accounts depleting the turion bank, which is the source of (summarized in Bolduan et al. 1994). The onset new plant colonies. Long-term control could be of turion sprouting in Blue Lake was similar to achieved by managing curlyleaf pondweed in published accounts (October); however, early to mid-spring when plants are young and sprouting lasted much longer (seven versus three prevent new turion formation. Moreover, timing months). Peak sprouting was noted in February management in the spring may improve the while peak sprouting in the Midwest occurred selective potential of various techniques since during September through November many native plant species are still dormant. (Wehrmeister 1978, Woolf and Madsen 2003). Research has shown that aquatic herbicides have Studies are ongoing. been effective in selectively managing curlyleaf In contrast to the Midwest, current management pondweed using a spring application strategy efforts for curlyleaf pondweed in the Pacific (Netherland et al. 2000, Poovey et al. 2002, Northwest have been limited. Although Skogerboe et al. 2008). curlyleaf pondweed is spreading throughout Lake Pend Oreille, ID, a concerted management Management techniques are relatively effort has not been undertaken. Management expensive. Prevention is one of the best and efforts in Oregon have been limited to Blue most effective methods to avoid aquatic weed Lake. In Washington, a formal request for problems. Weed watch programs and boat management information may be made to the inspection/cleaning stations are examples of Department of Ecology. Point of Contact is Jon preventative measures. These require Jennings, Water Quality Program, email: commitment, education and planning on the part [email protected], phone: 360-407-6283. of volunteers. Formal requests are processed in 30 days.
Current research and management efforts
Current research on curlyleaf pondweed in the Pacific Northwest is being conducted by the Center for Lakes and Reservoirs at Portland State University. Wells and Sytsma (2006) recorded the time of turion formation and sprouting in Blue Lake, OR. They found that curlyleaf pondweed initiated turion formation earlier (April) and formation lasted longer (nine Table 1. Management techniques for pioneer colonies of curlyleaf pondweed (Madsen 2000).
Management Description Advantages Disadvantages Plant Species Method Response
Hand- Cutting/ Direct hand pulling or Low-technology, Labor-intensive, cost is labor- Very effective in Pulling use of hand tools affordable, can be based very localized areas selective
Diver-Operated Vacuum lift used to Moderately selective Slow and cost-intensive Reduces biomass, Suction Harvester remove plant stems, (based on visibility and but not effective for roots, leaves, operator), longer-term depleting turion sediment left in place bank
Benthic Barrier Use natural or Direct and effective, Expensive and nonselective Nonselective, plant synthetic materials to may last several mortality within one cover plants seasons month
Weed Roller Mechanically disturb Affordable and low disturb bottom dwelling Effective for the lake bottom maintenance organisms, nonselective, clearing areas resuspension of sediments around docks
Table 2. Management techniques for curlyleaf pondweed infestations (Madsen 2000).
Management Description Advantages Disadvantages Plant species Method response
Grass Carp / Herbivorous Fish Long-term (decades), Cannot control feeding sites, Fish have moderate White Amur relatively inexpensive difficult to contain in water preference for body, tendency for "all or none" curlyleaf pondweed community response, persistent and higher preference for some native plants
Aquatic Short (12-36 Rapid action, limited drift Does not affect underground Broad-spectrum, herbicide: Diquat hours) portions acts in 7 days
Aquatic Short (12-36 Rapid action, limited drift Does not affect underground Broad spectrum, herbicide: hours) portions acts in 7-14 days Endothall
Aquatic Very long (30-60 Very low dosage required, Very long contact period Broad spectrum, herbicide: days) few label restrictions, acts in 30-90 days Fluridone systemic
Harvesting (Cut Mechanical Removes plant biomass Slower and more expensive than Like cutting, it is and Remove) cutting with plant cutting; resuspension of cosmetic, non- removal sediments selective short-term
Rotovating Cultivator on Disrupts plant stem bases, May spread large numbers of Effective in long arm for intermediate-term results fragments; resuspension of disrupting dense tilling aquatic sediments plant stands; not sediments selective and only intermediate-term Literature cited James WF Barko JW Eakin HL and Sorge PW (2003) Phosphorus budget and Arber A (1920) Water plants: A study of aquatic management strategies for an urban angiosperms. Cambridge University Press, Wisconsin lake. Lake and Reservoir Cambridge. Management 18:149-163.
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Wells S and Sytsma M (2006) Phenology of Experts in the Pacific Northwest Potamogeton crispus L. in Blue Lake, Oregon: Timing of turion formation and Jenifer Parsons Washington Department sprouting. Proceedings of the 26th Annual of Ecology Meeting of the Aquatic Plant Management [email protected] 360-407-6679 Society, July 16-19, Portland, OR. Botanist in the Environmental Assessment Program. Tracks aquatic plant community Woolf TE and Madsen JD (2003) Seasonal changes in lakes and rivers throughout plants biomass and carbohydrate allocation throughout Washington, concentrating on patterns in southern Minnesota curlyleaf invasive non-native species. Maintains aquatic pondweed populations. Journal of Aquatic plant monitoring database. Plant Management 41: 113-118. Mark Sytsma Center for Other resources Lakes and Reservoirs, Portland State University [email protected] 503-725-3833 An on-line version of the Aquatic Plant Director of the Center for Lakes and Reservoirs Identification Manual for Washington's and co-author of the Oregon Aquatic Invasive Species Management Plan. Conducted research on the reproductive ecology of curlyleaf pondweed in Oregon.
Tom Woolf Idaho State Department of Agriculture [email protected] 208-332-8564 Aquatic Plants Program Manager with expertise in the ecology and management of curlyleaf pondweed. Published research on the life cycle of curlyleaf pondweed in the Midwest.