creeping Jenny (Invasive Plants of Maryland)

creeping Jenny

Lysimachia nummularia

Description ⁴

This introduced perennial plant is a non-climbing vine up to 3' long that freely branches at the base. The light green stems are hairless and somewhat angular or ridged. The opposite leaves are about 11½" across and amply separated from other pairs of leaves on the stems. They are orbicular, orbicular-cordate, or orbicular-oval in shape, smooth along the margins, and hairless. The upper surface of the leaves is often shiny and has widely scattered glandular black dots. The leaves have short hairless petioles about ¼" in length. From the axil of each leaf, there occasionally appears a single yellow flower on a short pedicel. Each flower is about 1" across, consisting of 5 yellow petals (actually petal-like lobes of the corolla), 5 yellow stamens, a single green pistil, and a green calyx with 5 triangular or broadly lanceolate teeth. This calyx is hairless and its teeth are shorter than the petals. The petals have scattered glandular dots that are dark red. On rare occasions, some plants will produce flowers with 6 petals and 6 stamens. The blooming period occurs intermittently from late spring to late summer, and can last 2-3 months for a colony of plants, although usually few flowers are produced, which bloom during daylight hours. Rarely are seed capsules produced by these flowers. When it occurs, a seed capsule is ovoid in shape and has 5 cells, each cell containing several closely packed seeds. Moneywort often forms new roots at the axils of the opposite leaves, generating new stems that have a tendency to spread across the ground in all directions. These roots are rather slender and fibrous. Moneywort often forms vegetative colonies.

Impacts and control ⁵

More info for the terms: cover, fire management, forbs, frequency, invasive species, natural, prescribed fire, swamp

Impacts: A variety of fact sheets, government publications, and weed management guides suggest that moneywort populations form dense mats that may exclude other plants, including native species [28,29,36,40,97,105]. Moneywort's ability to dominate an area is attributed to its fast vegetative spread [28,36,61]. In floodplain forest of the lower Wisconsin River, moneywort was absent from a silver maple-green ash-elm (Ulmus spp.) floodplain forest in the 1950s but was one of the most frequent groundlayer species (second only to reed canarygrass (Phalaris arundinacea)) about 50 years later. The forest had become wetter over the 50 years, and there was an apparent loss of 2 native species possibly as a result of moneywort and reed canarygrass spread [32].

Although moneywort can occasionally become dominant in plant communities (e.g., [46,97]), it typically does not substantially modify natural habitats over large areas [68]. Most fact sheets, government publications, and weed management guides indicated that moneywort had no more than a moderate impact on native vegetation [20,68,83,104,117]. In a western Massachusetts silver maple-pin oak-green ash/buttonbush floodplain swamp forest, moneywort changed little in frequency and cover over approximately 27 years (1969: <0.5% cover, 2% frequency; 1996: 1% cover, 9% frequency) [39].

Control: Moneywort control may be complicated by its ability to sprout from stems and possibly roots following control treatments [20,45,105]. A fact sheet suggested that control efforts should focus on cessation of planting, management of existing infestations, and minimization of disturbance to forests, wetlands, and other natural communities [105]. Control effectiveness may depend on a program that integrates multiple management procedures such as herbicides, prescribed fire, seeding, and other techniques that decrease moneywort spread and favor desired species [45,105].

In all cases where invasive species are targeted for control, no matter what method is employed, the potential for other invasive species to fill their void must be considered [10]. Control of biotic invasions is most effective when it employs a long-term, ecosystem-wide strategy rather than a tactical approach focused on battling individual invaders [58].

Prevention: A fact sheet suggests that moneywort establishment may be prevented by minimizing soil disturbance [105]. Consumers should also avoid purchasing and planting moneywort [20,105].

It is commonly argued that the most cost-efficient and effective method of managing invasive species is to prevent their establishment and spread by maintaining "healthy" natural communities 58,89 and by monitoring several times each year [43]. Managing to maintain the integrity of the native plant community and mitigate the factors enhancing ecosystem invasibility is likely to be more effective than managing solely to control the invader [38].

Weed prevention and control can be incorporated into many types of management plans, including those for logging and site preparation, grazing allotments, recreation management, research projects, road building and maintenance, and fire management [106]. See the Guide to noxious weed prevention practices [106] for specific guidelines in preventing the spread of weed seeds and propagules under different management conditions.

Fire: For information on the use of prescribed fire to control this species, see Fire Management Considerations.

Cultural control: Some sources indicate that moneywort may be controlled by establishing native grasses that shade out moneywort [45,105]. However, a fact sheet noted that moneywort can tolerate shading by taller grasses and forbs [36]. For more information on this topic, see Shade tolerance.

Physical or mechanical control: Activities that disturb moneywort plants, such as hand-pulling, may stimulate growth of new plants from fragmented stems and possibly roots or rhizomes. Management guidelines suggest that small infestations of moneywort may be eradicated by carefully digging out plants; however, all stems and roots must be removed for this technique to be effective [20,45,105]. In a seasonally flooded wetland prairie in the Willamette Valley, Oregon, moneywort cover declined 1 and 3 years after hand removal compared to pretreatment levels, but the difference was not significant. Moneywort cover also declined in control plots during the study [16].

Two sources reported that mowing does not control moneywort because the plants are typically too low to the ground to be impacted by mowing blades [45,105]. Moreover, physical disturbance by machinery may spread moneywort across fields. Fleming and Kanal [24] speculated mowing equipment may have spread moneywort from a lawn in Washington, DC, into nearby meadows and roadsides. In the Montezuma National Wildlife Refuge in central New York, moneywort was not present in grasslands succeeded to gray dogwood (Cornus racemosa), common buckthorn (Rhamnus cathartica), and multiflora rose (Rosa multiflora) prior to mowing, but moneywort cover ranged from 0.6% to 0.9% 3 years after mowing. Moneywort was not present in control plots [84]. Several researchers reported moneywort in areas mowed annually or more frequently (e.g., [13,34,92]). In a seasonally flooded tall oatgrass (Arrhenatherum elatius) grassland in the Netherlands, mowing in June and again in September increased moneywort frequency during 8 years. The authors suggested that repeated reduction of grasses increased the frequency of moneywort and other low-lying plants. Moneywort frequency decreased or remained unchanged in areas mowed annually. Moneywort was absent in unmowed areas [70].

Some publications reported that moneywort may be killed by prolonged submergence in water [45,105]. However, a study in East Bohemia reported that moneywort survived flooding that covered the entire plant and that moneywort seed production was perhaps favored by the flooding [49]. For more information on this study, see Seed production. For more information on moneywort's soil moisture tolerance, see Site Characteristics.

Biological control: No biological controls of moneywort are known [45]. In the northern Front Range of Colorado, Al-Doghairi and Cranshaw [1] observed little to no visitation of moneywort by native arthropods typically used in biological control of pest plants (e.g., lady beetles (Coccinellidae), green lacewings (Chrysopidae), syrphid flies (Syrphidae), parasitic wasps (Braconidae), predatory wasps (Sphecidae), and techinid flies (Tachinidaea)).

Biological control of invasive species has a long history that indicates many factors must be considered before using biological controls. Refer to these sources: [109,118] and the Weed control methods handbook [102] for background information and important considerations for developing and implementing biological control programs.

Chemical control: Herbicides may control moneywort, although little information regarding the effectiveness of herbicides on moneywort was available as of this writing (2011) [45,105]. Herbicides are effective in gaining initial control of a new invasion or a severe infestation, but they are rarely a complete or long-term solution to weed management [11]. See the Weed control methods handbook [102] for considerations on the use of herbicides in natural areas and detailed information on specific chemicals. Integrated management: Integrated management includes considerations of not only killing the target plant but also of establishing desirable species and maintaining weed-free systems over the long term. Integrated management techniques may be more effective than individual methods at controlling moneywort, but as of this writing (2011) no information was available on this topic.