Glechoma hederacea L.

More info on this topic.

More info for the terms: cover, density, frequency, ramet, restoration, tree

Detailed information about ground-ivy's successional patterns in its native and nonnative ranges is lacking; however, available data suggests it can adapt to a variety of light regimes and establishes well on disturbed sites.

Shade tolerance: Several morphological adaptations may allow ground-ivy to thrive in shade (see Growth). In the United States, ground-ivy has been commonly reported growing in the shade of forests [40,47,56,70,86,119] and thickets [45,94,107,118], and a few studies indicate that ground-ivy may have a preference for shade [38,86]. In a riparian forest in Maryland, frequency of ground-ivy was greatest on the site with the lowest light levels [86]. Ground-ivy made up about 0.7% of the vegetation cover in a 50- to 100-year-old oak (Quercus spp.) forest in the southern Appalachian Mountains of Virginia that had not been managed for the past 15 to 25 years [38]. A study in England determined that frequency of ground-ivy increased significantly (P<0.05) over a 30-year period after tree harvesting was reduced [15]. In Great Britain, ground-ivy can establish under the dense shade of dog's mercury (Mercurialis perennis) [91].

While ground-ivy may be shade tolerant, its distribution does not appear to be age-sensitive or restricted to older forests [115]. In North America, ground-ivy can grow in full sunlight [113], and in Great Britain it is found growing in habitats in nearly full sun [51]. Ground-ivy's ability to establish and dominate on sites of variable light availability suggests that there may be factors besides shade that influence this species' ability to establish at various successional stages.

Increased shade may limit growth and reproduction of ground-ivy. In a laboratory, increases in the percentage of far-red light, typically associated with canopy shading, may decrease germination in ground-ivy (C.P.D. Birch, unpublished data, as cited in [51]). In the United Kingdom, researchers found that more flowers develop on clones growing on open sites; however, seed set was greatest in shaded habitats (review by [51]). Some researchers in England have observed the total elimination of ground-ivy with increasing canopy cover. Ground-ivy ceased to persist in a thinned woodland 3 years after thinning operations had been completed, suggesting that increased canopy cover may have inhibited its growth [2].

Establishment and persistence on disturbed sites: Several attributes make ground-ivy an effective invader of disturbed sites. Successful establishment of ground-ivy on disturbed sites may be facilitated through rapid stoloniferous growth and subsequent ramet production if a clone is nearby [6]. In a laboratory setting, fragmented stolons with a sufficient root system rapidly developed into physiologically autonomous segments, a characteristic that might enable ground-ivy to exploit disturbed habitats [7]. Ground-ivy has the ability to adapt morphologically to changes in the environment (e.g., light, nutrients) [99,102], giving it an advantage in variable conditions typically associated with disturbance. Its ability to produce greater mass under heterogeneous growing conditions [6] (see Growth) may make it a strong competitor on disturbed sites. Ground-ivy can also establish and grow in heavily compacted soils [32,91], which are often associated with disturbed sites.

Information pertaining to ground-ivy's persistence and density following disturbance is limited. Ground-ivy occurred in 1 or more hurricane impacted plots in a deciduous forest in North Carolina 4 years after the hurricane [109]. In another region of North Carolina, ground-ivy was found in a deciduous urban riparian forest invaded by English ivy (Hedera helix) that experienced intense recreational pressure [116]. In New York, ground-ivy was a dominant species in a fallow field where cultivation had ceased for approximately 20 years but mowing continued [81]. It was commonly found in portions of the floodplain on the Potomac River that were greater than 3.3 feet (1 m) from the water's edge [86]. Ground-ivy established in a recently planted tallgrass prairie restoration site in Illinois that had been previously cultivated [48].

Ground ivy occurs throughout the U.S. in all of the Lower 48 except for Nevada, Arizona and New Mexico and has been reported to be invasive in natural areas from Wisconsin to Connecticut, south to Tennessee and North Carolina. It is common in moist areas such as floodplains, low woods and disturbed sites and is a significant weed in lawns. It grows on damp, heavy, fertile and calcareous soils and does not tolerate highly acidic or saline soils.

Canada

Rounded National Status Rank: NNA - Not Applicable

United States

Rounded National Status Rank: NNA - Not Applicable

More info for the terms: density, frequency, presence, restoration

Research pertaining to ground-ivy's seed bank longevity, density, and vertical distribution in the soil differs in methods, location, and emphasis, making it difficult to derive specific inferences from. Some ground-ivy seeds apparently go through a period of physiological dormancy before they germinate (review by [4]), suggesting potential for at least short-term persistence in the soil seed bank (see Germination). Additional research is necessary to understand ground-ivy's seed banking potential in North America.

As of 2009, only two studies were found from North America that included seed banking information for ground-ivy. Using a seedling emergence method, ground-ivy was found in both the aboveground vegetation and the soil seed bank in an abandoned cultivated field undergoing restoration; however, researchers did not indicate to what extent ground-ivy was present in either stratum or report the estimated age of the seed [68]. Although ground-ivy was present in the aboveground vegetation in a Pennsylvania forest, it failed to germinate from core samples collected from the top 4 inches (10 cm) of soil from the site [66].

Available English language literature from Europe suggests ground-ivy's longevity in the soil seed bank may be highly variable; however, many studies failed to report to what extent ground-ivy occurred in the existing vegetation, making it difficult to draw conclusions about ground-ivy seed bank longevity. A review of seed bank literature in northwestern Europe [111] cites several studies suggesting that ground-ivy has only a transient soil seed bank (seeds persist for less than 1 year). A 20-year study on soil seed banking potential of weeds in a cultivated field in England found that ground-ivy seeds failed to germinate after the first 4 years of the study; however, continuous cultivation and herbicide treatments in this field may have influenced ground-ivy's persistence, seed dispersal, and seed longevity [13]. Other evidence indicates that ground-ivy seeds may remain viable in the soil for longer periods under some conditions. Researchers in Russia found viable ground-ivy seed buried at soil depths from 1.6 to 2.4 inches (4-6 cm) in a spruce plantation that was approximately 40 years old (Petrov and Palkina 1983, as cited in [51]). In an arable field in the United Kingdom, researchers found viable ground-ivy seeds at soil depths from 0 to 4.7 inches (0-12 cm) about 19 years after cultivation had ceased (Stag 1996, as cited in [51]). In 1963, excavation of a 460-year old monastery site uncovered viable ground-ivy seeds at soil depths between 21 and 29 inches (52-73 cm). The monastery and its associated buildings were gone by the mid-1500s but the land continued to be cultivated until 1935, suggesting that the ground-ivy seed found on this site is a remnant of recent cultivation activities rather than persistent in the soil for 460 years [80].

Reports on ground-ivy seed bank densities and the vertical distribution of its seeds in the soil are variable. A literature review on seed banks in northwestern Europe cites several reports on soil seed bank densities for ground-ivy. Seed densities ranged from 0 to 281 seeds/m² for various soil depths. However, the review did not report to what extent ground-ivy occurred in the aboveground vegetation, making it difficult to infer to what extent existing vegetation influenced seed banking. Additionally, different methodologies were used among studies, making comparison of the data difficult [111]. In a laboratory in Estonia, 17 ground-ivy seedlings emerged from a 4-inch³ (~63 cm³) soil core collected at a depth of about 2 to 4 inches (5-10 cm) from an early-successional (20- to 25-year-old) forest clearcut [132]. Stag (1996, as cited in [51]) determined that ground-ivy seed densities were greatest in the late summer, especially in the top 2 inches (5 cm) of soil.

Available evidence suggests that seed bank densities for ground-ivy may be site specific and influenced by localized environmental factors, making them difficult to characterize. Factors that may influence ground-ivy seed occurrence and densities include abundance of ground-ivy in the aboveground vegetation, frequency of flooding [114], soil acidity, shade, land management practices [120], and age of seed [80]. However, the presence and abundance of ground-ivy in the aboveground vegetation may not correspond to its presence and abundance in the soil seed bank [66,114].