Ground Ivy (Invasive Exotic Plants of North Carolina)

Ground Ivy

Glechoma hederacea

Summary ⁵

Glechoma hederacea (syn. Nepeta glechoma Benth., Nepeta hederacea (L.) Trevir.) is an aromatic, perennial, evergreen creeper of the mint family Lamiaceae. It is commonly known as ground-ivy, gill-over-the-ground, creeping charlie, alehoof, tunhoof, catsfoot, field balm, and run-away-robin. It is also sometimes known as creeping jenny, but that name more commonly refers to Lysimachia nummularia. It has numerous medicinal uses, and is used as a salad green in many countries. European settlers carried it around the world, and it has become a well-established introduced and naturalized plant in a wide variety of localities.

Ecological threat in the united states ⁶

Ground ivy is a vigorous grower that spreads across the ground forming dense patches that push out native plants. It is toxic to many vertebrates, including horses, if eaten in large quantities either fresh or in hay.

Impacts and control ⁷

More info for the terms: cover, fire management, invasive species, mesic, natural, prescribed fire, shrubs

Impacts: Although ground-ivy is found throughout much of North America, north of Mexico, no specific information was available as of this writing (2009) regarding its impacts on native plant communities and ecological processes across this range. The lack of data pertaining to ground-ivy's impacts suggests that it may be less invasive and widespread than other invasive species that have been well documented. However, ground-ivy's ability to exploit heterogeneous resources [6,51], allelopathic potential [89], ability to regenerate vegetatively [7,103,125], and its early bloom time may provide opportunity for it to spread into native plant communities. The shade-tolerant nature of ground-ivy makes it problematic because it can invade under a forest canopy (see Shade tolerance)

A few regional weed publications and floras have reported on ground-ivy invasiveness. In Connecticut, distribution of ground-ivy is banned because of its invasive potential [112]. In Virginia, ground-ivy is ranked as a "moderately invasive species" in mesic, partly sunny to shaded habitats. Species ranked as moderately invasive may have a minor influence on ecosystem processes, alter plant community composition, and affect community structure. Usually some type of disturbance is necessary for these species to establish, and they may dominate the understory layer [117]. In Kentucky, ground-ivy is considered a "significant threat" that may have the capacity to invade natural plant communities associated with disturbance [57]. Ground-ivy is ranked as a Category B invasive plant in Missouri. Species in this category are occasional invaders of native plant communities in Missouri or are invasive in other states with similar habitats, but with generally low levels of impact [75]. In the upper midwestern United States, ground-ivy is categorized as a lesser invader in forests and woodlands and "is generally not a threat to established native plant communities except along woodland edges" [17]. In the Intermountain West area of the United States ground-ivy is described as "too aggressive for most areas" [46]. In Canada, ground-ivy is considered a potential threat to native habitats and is listed as a species of concern [12], and in Nova Scotia, it can be "almost impossible to eradicate" around sites associated with human habitation [94].

Ground-ivy's greatest impact may be to lawns and turfgrass [3,35,43,45,60,74,118] where it can form dense mats that eliminate desirable vegetation [17,105]. In Ohio, ground-ivy was reported to "grow like mad" in home lawns [28]. It disrupts turf uniformity and is difficult to control in these environments [60]. While reports suggest ground-ivy can grow in full sunlight, some turf care professionals report that it usually prefers shaded turf [105]. Ground-ivy has become such a nuisance to the turf management industry that research has been launched to evaluate different control methods for ground-ivy [60].

Control: Information related to the control of ground-ivy has been derived primarily from the turfgrass maintenance industry but may have some application to wildlands.

Fire: For information on the use of prescribed fire to control ground-ivy see Fire Management Considerations.

Prevention: As of 2009, no information is available on this topic.

Cultural control: The turfgrass industry has suggested that the use of shade-tolerant grasses and other species that are better adapted to shade may deter ground-ivy's spread in turfgrass [105].

Physical or mechanical control: Ground-ivy's ability to regenerate vegetatively (see Vegetative regeneration) makes it hard to control by physical or mechanical means. Turfgrass researchers assert that extensive rooting from stolons would make mechanical control difficult [60,105]. In the midwestern United States, small patches of ground-ivy may be controlled by carefully pulling or raking out the plants when the soil is damp, but great care needs to be taken to remove all roots because stems easily break [17]. In central New York, a grassland managed for control of invasive shrubs experienced little increase or a slight reduction in ground-ivy cover on 3 plots treated with various rotations of brushcutting over a 2-year period. Ground-ivy cover increased more on a control plot than on treated plots (see table below). In another nearby managed grassland, ground-ivy cover increased over a 2-year period from 0% to 12.5% in a plot that was mowed and mulched. Ground-ivy also increased on control plots but to a lesser degree than on the treated plot (from 1.1% to 2.3%) [90]. For more details on this study see Fire Management Considerations. Percent cover of ground-ivy in plots treated with various rotations of brushcutting over 2-year period at Clark Ridge grassland in New York [90]. Treatment date Control Growing season cut
(once/2-yr period) Growing season cut
(twice/2-yr period) Dormant season cut
(once/2-yr period) Prior to 2001 1.9 2.5 5.8 3.6 After 2003 5.3 3.7 8.6 3.2

Biological control: As of 2009, no information is available on this topic; however, herbivory on ground-ivy by invertebrates is common in this plant's native range [51], suggesting that there may be potential for a biological control.

Chemical control: As of this writing (2009), no information was available regarding chemical control of ground-ivy in wildlands. Ground-ivy may be difficult to control chemically in lawns and turfgrass [43,60] but a few publications recommend specific treatments [17,28,42,43,60,105]. Used independently, postemergent herbicide treatment may fail to control ground-ivy because it can quickly reestablish if any ramets or stolons survive [60].

Integrated management: Information pertaining to integrated management techniques for ground-ivy comes from 1 study in central New York where ground-ivy's occurrence was incidental to the study. In a managed grassland (i.e., 10 years of rotational mowing and prescribed fire to control invasive shrubs), ground-ivy increased over a 2-year period on 2 plots treated with a combination of mowing/cutting and low-intensity prescribed fire. Ground-ivy also increased on control plots but to a lesser degree than on treated plots [90]. For more details on this study see Fire Management Considerations and Physical or mechanical control.

Control ⁵

As is often the case when a plant has this many familiar names, Glechoma is familiar to a large number of people as a weed, a property it shares with many others of the mint family. It can be a problem in heavy, rich soils with good fertility, high moisture, and low boron content. It thrives particularly well in shady areas where grass does not grow well, although it can also be a problem in full sun.

Small infestations can be controlled through hand weeding; repeated weeding is required because the plant is stoloniferous and will continue to spread from its roots or bits of stem which reroot.

Glechoma is unusually sensitive to boron, and can be killed by applying borax (sodium tetraborate) in solution. The ratio is eight to ten ounces (225–275 g) of borax dissolved in four ounces (125 ml) of warm water, diluted to 2.5 U.S. gallons (10 l) of final solution, to be sprayed evenly over precisely 1,000 square feet (100 m²) of lawn. Borax is toxic to other plants and to animals at only slightly higher concentrations and it does not break down in the environment; therefore the long-term effects of this technique on soil or groundwater, although not well documented, can be assumed to be unfavorable. More recent research discounts the efficacy of borax, primarily because finding the correct concentration for a given area is difficult and the potential for damaging desired plants.

Aside from mechanical removal or borax treatment, the other alternative for Glechoma infestation is use of commercial herbicides. There is some disagreement over the effectiveness of various herbicides, with dicamba (Trimec and Weed-B-Gon) and 2,4-D being described variously as both effective and ineffective by different sources. Some or all of the disagreement may be due to the existence of subpopulations which have differing susceptibilities to different compounds, as well as to differing rates of application. To avoid generating herbicide resistance, the same product should not be used several years in succession; rather, various products should be used in rotation. Triclopyr has also been described as effective, and Clopyralid, MCPP, and quinclorac as ineffective. Fluroxypyr and Confront have also been described as effective, but sales of both are restricted to professionals. Two applications ten to fourteen days apart are necessary; also, the ability of the surviving plants to regenerate after 24 days can require a second treatment four or five weeks later, and even more followups.

In addition, the timing of application may play a role in the effectiveness of the herbicide, as well as the perception of effectiveness. For instance, fall is usually the best time for use of broadleaf herbicides; however, a slow-acting herbicide like triclopyr applied in the fall may not appear to have been effective until the next growing season.

Other techniques reported effective are to fertilize with greater than two pounds of nitrogen per thousand square feet annually, and use of preemergent herbicides, isoxaben. In extremely difficult cases, a short-lived full-spectrum herbicide such as glyphosate is used to kill the entire lawn, and it is reseeded from start.

Sources and Credits

(c) Matthew O'Donnell, some rights reserved (CC BY-NC-SA), http://www.flickr.com/photos/lycaenidae/8663393719/
(c) schmakca, some rights reserved (CC BY-NC)
(c) Melissa McMasters, some rights reserved (CC BY), https://www.flickr.com/photos/132545975@N04/17862878941/
(c) 2008 Zoya Akulova, some rights reserved (CC BY-NC), http://calphotos.berkeley.edu/cgi/img_query?seq_num=262547&one=T
(c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Glechoma_hederacea
(c) Unknown, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/22733852
Public Domain, http://eol.org/data_objects/24628965

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Ground Ivy

Summary 5

Ecological threat in the united states 6

Impacts and control 7

Control 5