Authors: Bryan A. Endress, Catherine G. Parks, eds. Mandy Tu and Barry Rice, Global Invasive Species Team, The Nature Conservancy
- Potentilla recta is a perennial herb that can grow to 19.7 in. (50 cm) tall. It is native to Africa, temperate Asia and Europe.
- A loose rosette of long-petiolate leaves develops first and withers before flowering. Plants can be one or multi-stemmed. Stems are covered with long and short hairs and are unbranched. Cauline leaves are palmately compound (with 5-7 leaflets), stipulate and short petioled to sessile. The central leaflet is 1.2-5.9 in. (3-15 cm) long (longer than the other leaflets).
- Flowering occurs from May to July, when sulfur yellow flowers develop in open, flat-topped inflorescences at the apex of the stems. Flowers have 5 petals, each 0.2-0.4 in. (0.5-1 cm) long, and 25-30 stamens.
- Fruits are small, dark brown achenes with pale veins. Seeds often have a webbed or net-like pattern on them.
- Ecological Threat
- P. recta occurs in pastures, rangelands, along roadsides and other disturbed sites. NOTE: The native graceful or slender cinquefoil, P. gracilis has short hairs that lie flat on the stems and leaves and brighter yellow flowers than the invasive P. recta.
Scientific Name: Potentilla recta L.
The genus name Potentilla comes from the Latin diminutive of potens meaning "powerful" in reference to the medicinal properties of some species. The species epithet recta means straight, upright, erect.
Synonyms: Potentilla sulphurea Lam., Potentilla recta L. var obscura (Nestler) W.D.J. Koch., Potentilla recta L. var pilosa (Willd.) Ledb., Potentilla recta L. var sulphurea (Lam. & DC.) Peyr. (USDA, NRCS 1999, TROPICOS 2001).
Common Names: Sulfur cinquefoil is the most commonly used name for P. recta, though it is also referred to as ‘rough-fruited cinquefoil’ or ‘erect cinquefoil.’ In the past, it has been called ‘upright cinquefoil’ (Fernald 1950). The common names ‘five-finger’ and ‘cinquefoil’ are frequently used for the genus Potentilla.
DESCRIPTION AND DIAGNOSTIC CHARACTERISTICS
Potentilla recta is a perennial herb of the rose family (Rosaceae). Potentilla recta has a woody base with 1-8 stems, reaching 30-70 cm in height. Stems have few, if any branches. Leaves are alternate, palmately compound with 5-9 leaflets per leaf. Leaflets are serrate, oblong and 3-14 cm long (Werner and Soule 1976). The entire above-ground portion of the plant is covered with shiny, erect hairs that emerge at right angles from the plant. Plants have been reported to live up to 20-30 years in Michigan (Rice 1991) and 10 years in Oregon (Dana Perkins, pers. comm.). The plant has a single taproot, and may have several shallow, spreading branch roots, but no rhizomes. Flowers typically appear from late May to mid July in Oregon, and occur in cymes with 1-60 flowers per inflorescence (Endress, unpublished data). Flowers have 5 pale-yellow petals that are notched at the tip and are 1.5-2.5 cm in length (Rice 1999). Reproduction is only by seed. The seeds are dark brown comma-shaped achenes, 1-2 mm long with a net-like pattern of veins on the surface. Potentilla recta is often confused with native cinquefoils that are found in the Pacific Northwest, but can be easily distinguished by its 3 unique characteristics: 1) long, right angled hairs perpendicular to the leafstalks and stem, 2) numerous stem leaves but few basal leaves, and 3) a net-like pattern on its seed coat.
Potentilla recta, an herbaceous forb native to Eurasia, is well established throughout much of the United States and Canada, and is found in a wide range of natural and agricultural habitats. It is particularly problematic in the drier climates of the Pacific and inland Northwest where it invades grassland and open-forest communities and displaces native vegetation. Of particular concern is the impact of P. recta on native Potentilla species in the Pacific Northwest. A single plant can produce thousands of seeds annually which allows for its rapid spread.
Hand-digging may effectively control small infestations. There are no approved biological controls for P. recta. In large infestations, selective herbicides applied at recommended label rates are likely the only method of effective control. Picloram applied in the spring or fall provides effective control and offers multi-year residual activity. 2,4-D ester is suggested where water resources are an issue. No direct data are available on how long seeds remain viable in soil, but seedling re-establishment from the soil seed bank is likely, and thus repeated applications may be necessary. After control efforts, restoration activities that promote native vegetation reestablishment are likely the best approach for long-term control.
RANGE & HABITATS
Potentilla recta is native to Eurasia and is found in central and southern Europe, the mountainous regions of North Africa, and western and central Asia, where it is found in grass- or shrub- dominated communities, pine-forest clearings, and forest boarders (Schaffner and Tosevski 1994). It was introduced to North America before 1900. By the 1950s P. recta was well established in Canada, and the northeastern and upper Midwest of the United States (Rice 1999). The first known report of P. recta in western North America was on Vancouver Island in 1914 (Zouhar 2003). It has since spread throughout the continent, and has been reported in all states of the continental US, except for Arizona, Utah and New Mexico (USDA, NRCS 1999). The ten southernmost Canadian provinces have also documented the establishment of sulfur cinquefoil.
Potentilla recta is adapted to a wide range of environmental conditions and is able to establish in a variety of ecosystems. In eastern North America, P. recta is generally found along roadsides, rights-of-way, disturbed areas, and old fields, while in western North America, it has also invaded native forest, shrub and grassland plant communities. While P. recta is predominantly found in open-areas, such as in eastern Minnesota prairie sites (Bradley et al. 2003), it has also been observed under dense canopy cover (Endress, unpublished data). Potentilla recta does not seem to be limited by soil texture, but tends to form the largest infestations on coarse-textured soils, on drier sites at low and mid elevations, and on moderately moist sites at low elevations (Rice 1991). Dense infestations have also been found on sandy, gravelly, rocky, and clay soils (Rice et al. 1991, Werner and Soule 1976). In the Pacific Northwest and British Columbia, P. recta occurs in areas with 13-50 inches of mean annual precipitation. Potentilla recta generally does not occur in the Great Basin, desert Southwest, southern Rockies, or Rocky Mountain Piedmont. It is most problematic in Montana, Idaho, and eastern Washington and Oregon.
No systematic inventory exists that allows for a comprehensive understanding of which habitats are most susceptible to P. recta invasion. However, Zouhar (2003) provides lists of potentially susceptible ecosystems, physiographic regions, habitats, and plant associations. Because of P. recta’s wide latitude in ecological requirements, however, these lists are considerable and include deciduous and coniferous forests, sagebrush, grassland, pinyon-juniper, and savanna biomes, among others. In Montana alone, Rice (1993) found infestations in 14 plant communities ranging from forest to grassland communities. In addition, P. recta commonly co-occurs with native Potentilla spp. including P. arguta, P. glandulosa, P. gracilis and others (Rice 1993).
Potentilla recta can be very competitive displacing both native and non-native plants. In Oregon, Montana, and Idaho it invades bluebunch wheatgrass rangeland, and has also been reported to replace spotted knapweed on some sites in Montana (Rice 1991). In Northeastern Oregon, P. recta densities vary from 1 stem/m2 in ponderosa pine stands (75% canopy cover) to over 150 stems/m2 in degraded meadows (Endress, unpublished data). In Michigan a maximum density of 39 stems/m2 was reported (Werner and Soule 1976).
IMPACTS AND THREATS POSED
Potentilla recta can invade and dominate a variety of vegetation types. Roadsides, waste places, abandoned agriculture fields, clear cuts, and other disturbed sites are particularly susceptible to invasion by P. recta; however, low-disturbance sites, including native grassland, shrubland, and forest communities can also be invaded by P. recta. It can pose a serious management threat in many natural areas due to its prolific seed production. When plant communities become thoroughly infested by P. recta, native plant diversity often decreases and natural successional processes may become altered. Of particular concern is the risk that P. recta may pose to the abundance and reproductive success of the many native cinquefoils that frequently co-occur with P. recta in the interior Pacific Northwest. Studies have been initiated to determine if hybridization between P. recta and native Potentilla species occurs (Cronn, pers. comm.). In Europe P. recta is known to hybridize with P. hirta under natural conditions (Goswami and Acharya 1975). Investigations of the insect pollinator communities shared by P. recta and co-occurring native Potentilla spp. are ongoing (McIver, pers. comm.). Potentilla recta typically produces more flowers than co-occurring native Potentilla spp. and may therefore attract more insect pollinators, causing reduced reproductive success of native Potentilla species. Dry meadows infested with P. recta located at critical lower elevation winter range, may adversely affect deer and elk populations in northeastern Oregon due to loss of forage (Parks, unpublished information).
BIOLOGY AND ECOLOGY
Moisture, light and temperature
Potentilla recta can survive in a variety of environmental conditions. Reports suggest that P. recta does best in semi-arid locations with mean annual precipitation between 333-1270 mm/year (13.1-50.0 inches) and in areas with a Mediterranean climate (Powell 1996). Potentilla recta also seems to inhabit both slightly mesic and xeric sites. In the eastern U.S., P. recta is found in dry soil (Gleason and Cronquist 1991) and is reported to spread rapidly on xeric sites in Montana (Lesica 2002), while in Nevada it only occurs on wet or damp soil around lakes, ponds, and streams (Kartesz 1988).
Soil texture and soil pH
Little information exists on the importance of soil texture and soil pH on P. recta, though its wide distribution across North America suggests that it can tolerate a range of soil conditions. It has been found to colonize areas with sandy, gravelly, rocky, limey and clay soils (Rice et al. 1991, Werner and Soule 1976).
Reproduction & seed viability
Potentilla recta only reproduces through the production of seeds. There is no vegetative mode of reproduction. Flower and seed production appears to be greater in western North America than eastern North America. In Michigan, seed production for P. recta adults averaged 1650 seeds/plant, while in Northeastern Oregon seed production averaged 5350-5600 seeds/plant between 2001 and 2002 (Dwire et al. 2003). On a grassland site in northwestern Montana, the proportion of sulfur cinquefoil plants producing fruit ranged from 3 to 86% and was highest during years with highest precipitation (Lesica and Martin, 2003)
Seed dispersal occurs from late summer through fall. Seeds are wind-dispersed and travel an average 0.27 m from the parent plant (Dwire et al. 2003). Long-distance dispersal via animals (in fur, hooves, etc.), people (seed heads readily attach to fleece, jeans, and boots), and vehicles is also likely. In northeastern Oregon, cattle, deer, and elk have been observed consuming mature seedheads which may also facilitate the long distance dispersal of P. recta (Parks and Endress, pers. obs.). Seeds may also be carried in melting snow and surface flows.
Seeds appear to be persistent in the seedbank, though no research has been conducted to demonstrate this. Percent germination of P. recta seeds did not decrease with more than two years of burial (Baskin and Baskin 1990), and Rice et al. (1991) suggested that seeds remain viable in the soil for more than four years.
There are no reported uses for P. recta beyond use as an ornamental plant for gardens. Potentilla recta is not good forage due to its high tannin content (Werner and Soule 1976). It has been reported as unpalatable to most livestock and wildlife (Rice 1991, Rice et al. 1991, Werner and Soule 1976), though cattle, elk, and deer have been observed browsing P. recta in Oregon (C. Parks, and B. Endress, pers. obs.).
Potential for Restoration of Invaded Sites
As with all prolific invaders, prevention, early detection, and rapid action are the keys to the successful control of P. recta. Because abundant seeds reside in the soil surface of P. recta infested sites, careful cleaning of soil from equipment before moving it from infested to uninfested areas may prevent new infestations. Early detection of new colonies and an aggressive manual, mechanical or chemical control program may eradicate new colonies. No biological control methods are available and thorough integrated weed management techniques have not yet been developed to manage large infestations of P. recta. Combinations of prescribed fire, herbicides, and seeding of native grass species are being evaluated as management tools (Parks and Endress, unpublished information).
Manual and Mechanical Control
Hand digging may eradicate small infestations if care is made to completely remove root crowns. Populations must be monitored for several years following plant removal because seeds stored in the soil seed bank may germinate. Mowing is not an effective control method. In agricultural settings, tilling of the soil followed by seeding with more desired vegetation is likely an effective method for P. recta control, though this approach is impractical for P. recta control in most natural areas.
Improper cattle grazing of P. recta infested areas may accelerate the dominance of P. recta, if grasses and forbs are selectively removed by grazing. Studies to determine the influence of grazing on P. recta are needed. Potentilla recta is utilized in intensively grazed situations but can still flower and produce seeds even when heavily grazed (Parks, unpublished information). Goats are reported to select for P. recta (Rice 1999) Wild ungulates have been observed to browse P. recta, though this effect on P. recta demography is unknown. Potentilla recta is generally thought to be avoided by most grazing animals (Rice 1999); however 63% of P. recta stems in a degraded meadow in northeastern Oregon showed evidence of ungulate browsing in 2003 (Parks and Endress, unpublished data). Ingestion of seed heads, or attachment of seeds to the bodies or hooves of animals during grazing of infested sites may lead to establishment of new P. recta colonies if seeds are deposited in uninfested areas with grazing migration.
Using prescribed fires to control P. recta does not appear to be effective. In an experiment conducted to determine the effectiveness of prescribed fire, Lesica and Martin (2003) found that fire (spring or fall burns) increased P. recta recruitment as compared to unburned plots. Preliminary results from a similar study in northeastern Oregon also suggest that prescribed fire alone will not control P. recta infestations (Parks, unpublished data). However, integrated approaches incorporating prescribed fire, herbicide application, and seeding of native seeds may be effective.
Selective herbicides are currently the most effective means to control large infestations of P. recta. Picloram applied in either spring or fall is reported to provide several years of control, and Rice (1999) suggests application rates of 0.25 lb ae/acre when applied in the fall or spring up to late bud stage. On dry land sites picloram used at recommended label rates is preferred because its residual activity will inhibit new plants from establishing from the existing soil seed bank. Where water contamination is a concern 2,4-D ester also provides good control, but without the multi-year residual activity obtained from picloram.
There are no available biocontrol agents for P. recta. Due to the plant’s close genetic relationship to native Potentilla species and to cultivated strawberries, finding a host specific biocontrol agent for P. recta is difficult. However, screening for host-specific insects and fungi is ongoing (Jim Story, pers. comm.),
P. recta is a strong competitor and is capable of suppressing native vegetation. If P. recta populations are reduced (i.e., by herbicide, hand-digging), native plants are usually able to rapidly recolonize sites if sufficient native seed is still viable in the soil. Seeding of native species under adequate environmental conditions, reducing grazing pressure, and continued spot herbicide re-treatments, will result in a more rapid and stable restored native plant community.
EXAMPLES OF MANAGEMENT PROGRAMS
In 1992, Celestine Duncan conducted an experiment near Bozeman and Missoula, Montana to determine the optimum P. recta growth stage for applying picloram, metsulfuron, and 2,4-D ester. She found that picloram (.25 lb/acre) yielded best results 1 year after application with >94% control regardless of the timing of the application. When using 2,4-D, application during the rosette and bud stages yielded control rates >90% while application during flowering and fall regrowth periods yielded variable results, ranging from 35%-90%. Metsulfuron did not control P. recta at the Missoula site, but provided moderate control (53-79%) at the Bozeman site.
To determine the effectiveness of management treatments, monitoring should optimally occur prior to and after control efforts. Monitoring should be continued for several years following the treatments to determine whether the impacts are lasting and if your management actions are having the desired outcomes. Therefore, monitoring data should be able to assess changes in abundance (percent cover or density) of P. recta and desirable natives or “guilds” of natives over time.
Following initial control treatments, further control efforts and monitoring must be performed at least once-a-year for a minimum of 3-5 years, due to the longevity of P. recta of seeds in the seedbank, and the likelihood of re-invasion from nearby propagule sources.
Other conservation targets may be important indicators of ecosystem health. Monitoring the status of community attributes such as the growth and survival of restoration plantings, the regeneration of native plant species, invertebrates, and mammals, is as important as monitoring invasive species populations. In general, the objectives of monitoring should track those of management.
While usually considered a research technique, measuring change in both “control” (unmanaged) as well as in the treated areas can be an effective way of assuring that any changes detected in treated areas are actually the result of management actions and not due to other factors. In communities that are in early successional stages or which have been recently disturbed, declines in abundance of invasive species may occur over time without management.
Despite the widespread concern of P. recta invasion, very little is known about several fundamental issues. The following topics need to be researched:
1. How long do P. recta seeds remain viable in soil? It is reported that seeds can remain viable in the soil up to four years (Rice 1999). However, very little evidence supports this, and it is likely that seeds remain viable for a longer time period. Additional studies are needed to quantify seed viability as this can greatly alter control, management, and restoration methods.
2. Does P. recta displace native species, and if so, to what extent? Observations suggest that P. recta displaces native grasses and forbs. However, there have been no studies conducted that quantitatively demonstrate the impact of P. recta. Therefore, it remains unclear which species are directly at risk from P. recta invasion, or which plant communities are most greatly affected by P. recta.
3. What are the elements of a successful integrated management plan for long-term control and site restoration? Additional work is needed to order to develop integrated management strategies that successfully control P. recta while promoting invasion-resistant native plant communities. A considerable amount of work has gone into evaluating short-term methods of P. recta control (chemical, biological, manual). This work needs to be integrated with studies exploring the establishment and maintenance of native plant species in order to develop long-term management strategies.
4. What is the relationship between herbivory and P. recta? Since many areas are grazed by livestock or support native populations of deer and elk, it is important to answer such questions as whether these animals act as vectors of seed dispersal and design grazing management strategies that improve the ability of grazed plants to compete with P. recta.
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