Goutweed (Aegopodium podagraria), also known as bishop's-weed and snow-on-the-mountain, is an herbaceous perennial plant, one of several species of Aegopodium native to Europe and Asia. Most leaves are basal, with the leafstalk attached to an underground stem, or rhizome. The leaves are divided into three groups of three leaflets, making it "triternate." The leaflets are toothed and sometimes irregularly lobed. Foliage of the "wild" type is medium green in color; a commonly planted variegated form has bluish-green leaves with creamy white edges. Sometimes reversion back to solid green or a mixture of solid green and the lighter variegated pattern occurs within a patch.
Small, white, five-petaled flowers are produced in mid-summer. Flowers are arranged in flat-topped clusters (called compound umbels) and are held above the ground on a leafy stem up to about 3 feet tall. The seeds are small and elongate, similar in size and shape to carrot seeds, and ripen in late summer. In contrast to the dense foliage cover produced by goutweed, flowering shoots are uncommon in densely shaded areas.
The rhizomes of goutweed are long, white, and branching, superficially resembling those of quackgrass (Elytrigia repens, also known as Agropyron repens). Patches of goutweed typically form a dense canopy and can exclude most other herbaceous vegetation. Because of this, it is often used as a low-maintenance ground cover.
Goutweed is an aggressive invasive plant that forms dense patches, displaces native species, and greatly reduces species diversity in the ground layer. Goutweed patches inhibit the establishment of conifers and other native tree species as well. An ecologically versatile species, Goutweed is found in old gardens and flowerbeds, around shrubs and other plantings, and in a variety of other disturbed habitats such as felled forests, abandoned fields, and pastures. In Eurasia, goutweed is primarily a species of deciduous and southern boreal forests, and it expands aggressively in similar habitats in North America. Goutweed appears to do best on moist soil and in light to moderate shade, but is highly shade-tolerant and capable of invading closed-canopy forests.
Goutweed is currently known to occur in twenty-nine states in the mid-Atlantic, Northeast and Northwest (USDA PLANTS map) and is reported to be invasive in natural areas in Connecticut, Michigan, New Jersey, Pennsylvania, Vermont, and Wisconsin (WeedUS Database).
This description covers characteristics that may be relevant to fire ecology and is not meant for identification. Keys for identification are available (e.g., [28,52,58,71,74,76,92]).
Aboveground: Bishop's goutweed is a perennial ([52,62], review by [15]) herb [52,56,59,79,92,95] with erect, hollow stems (review by [14]). One review from the upper Great Lakes region indicated that bishop's goutweed grows from 4 to 12 inches (10-30 cm) tall [15], but it may grow to as tall as about 3 feet (1 m) in the northeastern United States [28]. In the Netherlands, bishop's goutweed grows from 1.5 feet (.47 m) [39] to 3 feet (1 m) tall ([59], review by [14]). Individual compound leaves are 1 to 3 inches (3-8 cm) long ([28], review by [15]). They are typically variegated but are occasionally all green [79], especially on plants established from seed [92]. Bishop's goutweed's inflorescence is a compound umbel [71,76] 2 to 4.7 inches (6-12 cm) wide [28]. Its seeds are about 1.4 mm wide [31].
Belowground: Information pertaining to bishop's goutweed's belowground morphology comes primarily from Europe. Bishop's goutweed has an extensive root system [41] that includes a main root and lateral roots. During early development, adventitious thick storage roots and thin feeding roots emerge from the hypocotyl. Eventually, additional adventitious roots form at rhizome nodes (review by [27]).
Bishop's goutweed has horizontal rhizomes [52,56,92] that may transition to vertical shoots at the end of the growing season (review by [27]). Reports of bishop's goutweed's rhizome length vary from 2 to 118 inches (5-300 cm) ([41,56], review by [27]). One study indicated that rhizomes are about 2 mm in diameter [56]. Nothing specific had been reported on how deep bishop's goutweed's rhizomes are buried in the soil as of 2009, but one review indicated that bishop's goutweed has a "weak shallow rhizome system" [34]. "Total" rhizome length may shorten as connections between ramets decay (review by [27]).
Stand structure: Bishop's goutweed exhibits clonal growth [59,62,74] and spreads by producing ramets ([59], review by [27]). In Massachusetts, bishop's goutweed forms dense mats (review by [95]). In Russia, bishop's goutweed's spatial distribution is nonrandom, and populations grow in clusters, presumably because of bishop's goutweed's rhizomatous nature [54].
Bishop's goutweed was introduced in North America from Europe [82]. In the United States, bishop's goutweed occurs from Maine south to South Carolina and west to Minnesota and Missouri. It also occurs in the Pacific Northwest from Montana to Washington and Oregon. It occurs in all the Canadian provinces excepting Newfoundland and Labrador, and Alberta. Plants Database provides a distributional map of bishop's goutweed.
Globally, bishop's goutweed occurs primarily in the northern hemisphere, particularly in Europe, Asia Minor ([28,36,58,92], reviews by [14,27]), and Russia (review by [27,63]). Bishop's goutweed's native distribution is unclear. It may have been introduced in England (review by [2]) and is considered a "weed" in the former Soviet Union, Germany, Finland (Holm 1979 cited in [14]), and Poland [44]. It is nonnative in North America [82] and Australia including Tasmania (reviews by [2,14]).
Bishop's goutweed is grown as an ornamental (reviews by [13,72]) and occasionally escapes cultivation ([28,58,71], review by [95]). Little information has been published on its rate and direction of spread in North America. Darlington (1859 cited in [50]) considered bishop's goutweed invasive in the eastern United States by 1859, but bishop's goutweed was still considered uncommon in New England in the early 1980s [76]. Subsequent reviews on invasive species in New England indicate that bishop's goutweed may be becoming more widespread in Vermont [91] and Massachusetts [55]. A flora from Nova Scotia indicates that bishop's goutweed was locally abundant and becoming common in North America by the late 1960s [74]. In the early 1970's Swink [82] described bishop's goutweed as an "occasional weed" in northern Illinois, and an Illinois flora states bishop's goutweed is infrequent and rarely escapes cultivation [58].
Fuels: As of this writing (2009) no information was available on bishop's goutweed's fuel characteristics.
FIRE REGIMES: With one exception, no published information was available at this time (2009) on North American plant communities where bishop's goutweed occurs, making it difficult to infer what FIRE REGIMES may be associated with bishop's goutweed. On one site in Illinois, bishop's goutweed occurred in a shaded ravine with box elder and slippery elm. FIRE REGIMES on this site may be similar to those described for wooded draws and ravines of the Great Plains. Surface or replacement fires may occur every 40 to 95 years, depending on moisture patterns and on the FIRE REGIMES of adjacent mixed-grass prairie and shrubland. Because native ungulates tend to concentrate in woody draws and ravines for food and cover, grazing may influence FIRE REGIMES and stand regeneration in these communities [48]. Find further fire regime information for the plant communities in which this species may occur by entering the species name in the FEIS home page under "Find FIRE REGIMES".
Seeds dispersed by bishop's goutweed plants in wildlands may have low germination rates [6], but in germination tests, bishop's goutweed seeds have shown moderate to high germination rates. In laboratory tests, 5% to 100% of bishop's goutweed seeds germinated after chilling at 41 °F (5 °C) [31,68,88].
At the time of seed dispersal, bishop's goutweed embryos are immature [25,68,88] and undergo a period of morphological and physiological dormancy before they germinate [68,88]. In Norway, 83% of bishop's goutweed seeds contained immature embryos, 15% contained endosperm but no embryos, and 2% were empty [25]. Before morphological dormancy can be broken, immature embryos must grow to full size; in the field, this process is triggered by cold temperatures in fall and early winter. An additional cold stratification period in the spring may be necessary to break physiological dormancy [88]. Several studies report that chilling of seeds induced bishop's goutweed germination. In the laboratory, exposure to temperatures of 41 °F (5 °C) for at least 16 weeks induced germination of bishop's goutweed seed [88]. In another study, no bishop's goutweed seeds germinated when fresh, but nearly all seeds germinated when exposed to 41 °F (5 °C) for 12 months [31]. A 3rd study [68] also induced bishop's goutweed germination at a temperature of 41 °F (5 °C) but obtained higher germination rates in a shorter time at 32 °F (0 °C). Vandelook and others [88] found that, once dormancy was broken, seeds germinated at constant and alternating temperatures ranging from 50 to 73 °F (10-23 °C).
Information about site characteristics where bishop's goutweed is invasive in North America is limited (2009). Information on sites where bishop's goutweed occurs comes primarily from European studies.
Climate: Bishop's goutweed occurs in temperate climates (see General Distribution). In Europe, mean precipitation on sites where bishop's goutweed occurred ranged from 19.5 [70] to 32.8 [26] inches (495-832 mm). Mean annual temperature was typically around 44 °F (7 °C), except where bishop's goutweed occurred in central Sweden, where average annual temperatures were as low as 42 °F (5.6 °C) [59].
Elevation: As of this writing (2009) no information is available on bishop's goutweed's elevational distribution in North America. Publications from Europe indicate that bishop's goutweed occurs at altitudes from 31 feet (10 m) [90] to nearly 3,488 feet (1,063 m) [33,45]. In one study from Sweden, bishop's goutweed was most common at altitudes from 1,030 to 1,120 feet (315-340 m) [33].
General habitat and moisture: Available evidence suggests that bishop's goutweed prefers moist conditions and may tolerate saturated soils. In the northeastern United States, bishop's goutweed is associated with moist sites [28]. In the upper Great Lakes region bishop's goutweed occurs on moist, well-drained soils [15]. In Australia, bishop's goutweed growth is "most prolific" in moist conditions and semishade (review by [14]). One review indicated that bishop's goutweed survives "very wet" conditions [72], and in Sweden, bishop's goutweed occurred on a site that was regularly flooded by an adjacent stream [33].
Leuschner and Lendzion [49] investigated microhabitat conditions for various herbaceous species in a beech forest in Germany and speculated that bishop's goutweed's occurrence was most influenced by relatively low soil moisture. On sites where bishop's goutweed occurred (i.e., open and sheltered valley sites, shallow and steep north-facing slopes) moisture content ranged from 33.2% to 36.4%; moisture content ranged from 25.2% to 28.1% on sites where bishop's goutweed was absent (i.e., rapid drying south-facing slopes) [49].
Microclimate and soil variables at 6 sites in a beech forest in Germany from March to May [49]
Variable
Valley North-facing slopes South-facing slopes open sheltered shallow steep shallow steep Bishop's goutweed cover (%) 15-25 15-25 3-5 1-3 0 0 Temperature (°C) 13.1 11.4 12.1 12.7 15.3 16.2 Relative humidity (%) 69.3 89.4 76.5 74.4 64 59.6 Vapor pressure deficit of air (Pa) 527 153 363 385 669 750 Photosynthetic active radiation (µmol/m²/s) 451 434 305 339 470 508 Soil moisture (volume %) 34.7 36.4 36.1 33.2 28.1 25.2 pH 7.3 7.1 7.2 7.4 7.3 7.3In North America, bishop's goutweed is associated with anthropogenically influenced habitats like roadsides and the sides of buildings [74,76]. In Canada, bishop's goutweed has escaped cultivation primarily to roadsides and "waste places" in southwestern British Columbia and from southern Manitoba to Nova Scotia [62,75]. Bishop's goutweed occurs in grasslands, forests, roadsides, "waste places", and gardens in the upper Great Lakes region [15] and in Michigan, it occurs on forest borders [92]. On 1 site in Illinois, it occurred in a shaded ravine [82]. In Connecticut, bishop's goutweed occurs in floodplains and on the edges of wildlands (review by [13]). In Vermont it occurs in riparian and upland forests (review by [91]), and in Massachusetts it occurs on uplands, wetlands, and on floodplains (review by [95]). In North Carolina and South Carolina, the all-green type of bishop's goutweed occurs on the edges of bogs [71].
Bishop's goutweed occurs on similar sites throughout Europe. It occurs in managed or abandoned grasslands [83,84] or in fields where mowing or grazing has occurred [26,65,66]. Its occurrence has been associated with gardens [6]. It occurs in wildlands, especially in open forests, forest edges [39,67,83,88], and riparian areas [83,88].
Substrate: In regions outside North America, bishop's goutweed is considered a nitrophilous species ([42,53,83,88], Ellenberg 1979 cited in [22]). Soil pH, however, may influence bishop's goutweed's distribution more than nitrogen concentrations [23,90].
Available evidence from Europe indicates that bishop's goutweed occurs in soil pH ranging from 3.1 [24] to 9 [94], but several publications indicate it is most commonly found in weakly acidic [23,24,33,61,66] to weakly basic soils ([49,102], Ellenberg and others 1992 cited in [89]). In Sweden, bishop's goutweed occurred in a forest on sites with soil pH from 4.0 to 7.0. Over a 30- to 35-year period, bishop's goutweed cover increased more rapidly on sites where pH was >6.5 than in more acidic soils [22]. In a greenhouse, bishop's goutweed occurred in soil pH ranging from 3.17 to 4.5 but was most frequent on soils in the higher portion of that range (less acidic) [23]. In Britain, bishop's goutweed's nitrogen uptake was greatest in soils of pH 7 [3]. Two publications from Europe indicate that bishop's goutweed occurs on limestone [49,93].
Information on other substrate characteristics associated with bishop's goutweed is patchy. In Belgium, bishop's goutweed occurred in a flat, low-lying forest on sandy loam and silty loam. A layer of sandy clay occurred at approximately a 3-foot (1 m) depth and impeded drainage [90]. In Sweden, bishop's goutweed occurred in soils covered with a thin layer of litter that persisted from autumn to spring and decomposed by summer. There was no or only a thin layer of humus below the litter layer [21].
Impacts: Reports on bishop's goutweed's impacts in North America are limited and anecdotal in nature. Reviews have described bishop's goutweed as an "aggressive" invader in the upper Great Lakes region [15], Vermont [91], and Massachusetts [55]. In New England, bishop's goutweed persists in wildlands and is locally abundant (review by [13]). It is considered invasive in northern Illinois [37] and Massachusetts [95]. The most detailed information comes from Vermont, where bishop's goutweed threatens forested and open areas and dominates the ground layer in some areas. It is a particular threat to native vegetation in floodplain forests (review by [91]). Reports on bishop's goutweed's impacts in Canada vary. Catling [11] considers bishop's goutweed to be a high-priority nonnative species in need of control because of its "major impacts" to wildlands in Canada. Others [62,97] consider bishop's goutweed a minor threat to native plant communities in Canada; however, White [97] cautioned that it may become locally abundant.
Bishop's goutweed invades native ecosystems outside North America (review by [72]). In the United Kingdom, it is considered a nuisance species [16]. A review from Australia describes bishop's goutweed as the "worst" of garden weeds. It spreads rapidly under favorable growing conditions; a single plant can cover an area of 10 feet² (3 m²) in 1 year [2].
Control: Regardless of what control method is employed, control of bishop's goutweed may be complicated by its rhizomatous nature. Reviews indicate that sprouting occurs if any rhizomes remain [95].
All-green bishop's goutweed may be more persistent [74] and spread more rapidly than variegated bishop's goutweed (see Seedling establishment and plant growth), making the all-green type particularly difficult to control [79].
Fire: As of this writing (2009), no information was available on the use of prescribed fire to control this species.
Prevention: 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 [51,78] (e.g., avoid road building in wildlands [85]) and by monitoring several times each year [38]. Preventing the establishment and spread of bishop's goutweed may be facilitated by preventing its escape from cultivation. One review from the upper Great Lakes region recommended planting bishop's goutweed only on sites not adjacent to wildlands and in gardens where root spread can be restricted (e.g., between a sidewalk and a house) (review by [15]).
Cultural control: No information was available as of this writing (2009).
Physical or mechanical control: A couple of reviews recommend hand pulling, raking, and digging followed up by monitoring to control bishop's goutweed [2,95]; however, caution must be taken to remove the entire rhizome and root system (reviews by [2,15,95]). Removing flowers before seed set may help control bishop's goutweed (reviews by [2,15]). Because bishop's goutweed's starch reserves are typically depleted by spring, Meyer [56] speculated that bishop's goutweed might be killed if it was prevented from photosynthesizing in the spring. Tree and shrub cutting, root trenching [102], hay making [26], and cattle grazing [65,66] may also reduce bishop's goutweed cover, but these methods have been developed for agricultural fields and may not be applicable to wildlands.
Biological control: No information was available as of this writing (2009).
Chemical control: One review from the Great Lakes region indicated that glyphosate could be applied to bishop's goutweed's foliage in spring or summer [15], but details on its effectiveness where not provided.
Integrated management: Attempts to combine herbicide with landscape cloth, bark mulch, and hand weeding to control bishop's goutweed in a garden were unsuccessful because sprouting occurred from either rhizomes or root fragments left in the soil (review by [13]).As of this writing (2009), little was known about bishop's goutweed's IMPORTANCE TO LIVESTOCK AND WILDLIFE in North America. The flowers of the Apiaceae family as a whole attract numerous insects with their nectar ([9], review by [103]). In Russia, bishop's goutweed is one of the most common plants and a "basic" source of nectar (review by [63]). In Switzerland, bishop's goutweed was 1 of only 2 plants out of 11 tested that were considered an "optimal" food source for parasitic wasps that have an important agricultural role [93]. In Sweden, 2 beetle species known to pollinate other plants were found on bishop's goutweed during anthesis [19]. In Poland, a patch of bishop's goutweed was completely eaten by a slug (Arion lusitanicus) [44].
Palatability and/or nutritional value: No information is available on this topic.
Cover value: In the Netherlands, a snail (Cepaea nemoralis) was found on bishop's goutweed leaves but did not eat them [99].
Little is known about bishop's goutweed's plant associates in North America, particularly where it may be most invasive. In Illinois [82] and the Northeast [28,76,91], bishop's goutweed occasionally occurs in wildlands. In Vermont, bishop's goutweed occurs in upland hardwood forests [91]. At one location in northern Illinois, bishop's goutweed occurred with boxelder (Acer negundo), slippery elm (U. rubra), black walnut (Juglans nigra), black raspberry (Rubus occidentalis), bristly greenbrier (Smilax tamnoides), great ragweed (Ambrosia trifida), eastern waterleaf (Hydrophyllum virginianum), and woodland lettuce (Lactuca floridana), and [82]. Based on its plant community associates in Europe, in North America bishop's goutweed may potentially occur in deciduous and coniferous woodland or forest communities and in plant communities with tall herbs.
Information from Europe indicates that bishop's goutweed most commonly occurs in deciduous woodlands and forests [21,24,53,67,101,102], especially in riparian areas [98]. It also occurs in shrublands, wetlands [46], and grasslands [26]. It typically occurs in plant communities characterized by tall herbs [83,84,98]. Bishop's goutweed sometimes dominates or codominates the herbaceous layer in plant communities and is a characteristic species for some plant communities outside of North America. In Sweden, it is a characteristic species for 2 plant community types, both dominated by buttercup (Ranunculaceae) species [67]. In Germany, there is a bishop's goutweed cover type that contains other tall herbs such as nettle (Urtica spp.) [83,84]. In the Czech Republic, bishop's goutweed dominated an abandoned grassland with tall grasses and forbs such as colonial bentgrass (Agrostis capillaris), meadow foxtail (Alopecurus pratensis), red fescue (Festuca rubra), and white bedstraw (Galium album) [26] and was codominant in a nitrophilous (species that prefer sites rich in nitrogen) plant community with stinging nettle (U. dioica) that occurs on anthropogenically altered sites (e.g., along roads, hedges, walls) [42]. In Estonia, bishop's goutweed dominates a wetland community type [46].
In North America, bishop's goutweed has been used as a ground cover (reviews by [13,95]).
Extracts from bishop's goutweed's roots have been used worldwide for their purifying and antiinflammatory properties [7]. There is evidence it has been used for treatment of gout in the past [69].
Literature pertaining to bishop's goutweed's phenology is sparse and comes primarily from locations outside North America. A few North American floras have reported flowering periods for bishop's goutweed. In Illinois, bishop's goutweed flowers from May to August [58], and a review from the Great Lakes region states that bishop's goutweed blooms in June [15]. In the northeastern United States, bishop's goutweed flowers from July to August [76]. In Nova Scotia, bishop's goutweed flowers and fruits from June through July [74].
The remainder of information, primarily from Europe, suggests a phenology that begins in early spring with seedling emergence, stem growth, and leaf development and culminates with plant senescence in fall after the first frost. In a garden in Belgium, bishop's goutweed seedlings emerged throughout the spring, but most emergence occurred in March and April [88]. In an outdoor experiment in Japan, cotyledons emerged by late April [68]. In Europe, bishop's goutweed seeds germinated in May or early June, and cotyledons photosynthesized for 1 to 2 months before dying. Primary rosette shoots develop soon after the cotyledons die (review by [27]). In Italy, optimal stem growth of bishop's goutweed occurred after mid-April [1]. In Germany, bishop's goutweed leaves begin to develop in early spring but are not fully expanded until May, when anthesis begins. Leaves stay green until August, when they begin to yellow, but they do not die until the first frost [56]. In Australia, bishop's goutweed's flowering stems emerge in midsummer [2].
In Switzerland [93], bishop's goutweed is insect pollinated, and it may be insect pollinated throughout its range. Bishop's goutweed emits a "strong" fragrance [9] and contains nectar on its nondeciduous floral parts (i.e., sepals, receptacle, gynoecium) [80]. It contains a number of volatile compounds that are suspected to influence insect-plant interactions [9,63], particularly those between bees and nectar-bearing plants [63]. In Sweden, pollinating beetles visited bishop's goutweed plants with fully developed flowers [19], although it is unclear whether beetles were acting as pollinators or just visiting the plants.
Bishop's goutweed has been described as both monocarpic [9] and polycarpic [8], but no details were given on how these determinations were made.
Bishop's goutweed seedlings are most likely to establish and survive under the forest canopy on well-lit sites where ground disturbance has occurred (e.g., animal digging) and on sites void of other plants (review by [27]). Because recruitment from seed is seldom seen in wild populations [59], seedling establishment may be rare. Even seedlings establishing in sunlight may die the same year they emerge because they compete poorly for water and nutrients compared to surrounding mature plants (review by [27]).
Gastuk [27] provides a detailed review of the process of bishop's goutweed development. Experiments in Japan indicate that bishop's goutweed cotyledons emerge in early spring after snowmelt and quickly develop primary rosette shoots [68]. A review from Europe indicates that during the next 5 to 7 years, lateral roots sprout from the main root, and horizontal rhizomes develop from axillary buds on the primary rosette shoot. Plants may reach reproductive stage 5 to 7 years after germination (review by [27]). Growth may be more rapid for clones that maintain rhizome connections, because connections allow for resource sharing between ramets in the sun and ramets in the shade [59]. Mature plants grow "vigorously" but eventually show signs of senescence and transition to a "post reproductive period" (review by [27]).
Some [74,79] consider bishop's goutweed plants with all-green foliage more "vigorous", spreading more rapidly than the variegated type. Higher photosynthetic rates in all-green plants may account for differences in growth. In a nursery, photosynthetic rates for variegated and all-green bishop's goutweed plants were comparable in full sun. However, in shade, photosynthetic rates for the all-green type were more than 50% higher than rates for the variegated type [79].
Throughout its range, bishop's goutweed prefers partial shade ([18,28,79,88], reviews by [14,15]) but tolerates deep shade ([18,49,76,82], review by [55]) with up to 90% canopy cover [33].
Although bishop's goutweed has some attributes of early successional species (e.g., establishes on disturbed sites), available evidence suggests it is not typically associated with early succession. Bishop's goutweed has limited regeneration from seed and its seed dispersal may limit its ability to establish on new sites. In Canada, bishop's goutweed does not normally grow in full sun. Photosynthetic tissue of the all-green type may be harmed if exposed to full sunlight; however, tissue on variegated plants may not be affected [79]. One review from Massachusetts indicated that bishop's goutweed grows in full sunlight [55] but provided no further details on its growth potential on such sites. In a previously mowed meadow in Poland, bishop's goutweed did not establish until year 15 of a 20-year-study even though viable seeds were collected from the soil during previous years of the study. Bishop's goutweed established only after the meadow had transitioned to a willow scrub community with a high proportion of sedges (Carex spp.) [20]. In Germany, bishop's goutweed occurred only on the floor of a deciduous forest and not in a newly vegetated patch of ground with pioneer species [17].
Outside of North America, bishop's goutweed occurs in mid- [90,101] to late-successional stages ([77,101], De Keersmaeker and Muys 1995 cited in [89], Pysek 1977 cited in [70]), and based on its affinity for shade, it may occur in similar successional stages in North America. Bishop's goutweed's abundance tends to increase over time ([20,24,53], Pysek 1977 cited in [70]), and it may become more abundant in late succession. For example, bishop's goutweed was common in a 100- to 130-year-old German beech forest [49] and in Poland, it attained greatest cover on woodland sites in late succession [100].
Verheyen and Hermy [89] speculated that bishop's goutweed's occurrence may only be moderately correlated with forest age (r² =0.51). Other factors, such as habitat quality, pH [89], nitrogen availability [24], and distance to an undisturbed population of bishop's goutweed [89], may influence the distribution of bishop's goutweed more than forest age.
Aegopodium podagraria, commonly called ground elder, is a species of flowering plant in the carrot family Apiaceae that grows in shady places. The name "ground elder" comes from the superficial similarity of its leaves and flowers to those of elder (Sambucus), which is not closely related. Other common names include herb gerard, bishop's weed, goutweed, gout wort, snow-in-the-mountain, English masterwort[2] and wild masterwort.[2] It is the type species of the genus Aegopodium. It is native to Europe and Asia, but has been introduced around the world as an ornamental plant, where it occasionally poses an ecological threat as an invasive exotic plant.[3]
This herbaceous perennial grows to a height of 100 cm (39 in) from underground rhizomes. The stems are erect, hollow, and grooved. The upper leaves are ternate, broad and toothed. It flowers in spring and early summer. Numerous flowers are grouped together in an umbrella-shaped flowerhead known as a compound umbel. The main umbel is further divided into several secondary umbels known as umbellets or umbellules. Each umbellet has 15 to 20 rays (pedicels) that are each topped with a single, small, five-petaled white flower.[4][5][6] They are visited by many types of pollinating insects.[7]
The fruits, produced in late summer and autumn, are small and have long curved styles.[8][9]
Aegopodium podagraria is distributed widely in the temperate zone of western Asia and the whole of mainland Europe.[10] It has been introduced elsewhere, including Ireland,[11] the United Kingdom,[12] the United States,[13] Canada,[13] Australia (including Tasmania),[14] New Zealand,[15] and Japan.[16]
Seed dispersal and seedling establishment are typically limited by shading, and new establishments from seed are restricted to disturbed areas. However Aegopodium podagraria readily spreads over large areas of ground by underground rhizomes. Once established, the plants are highly competitive, even in shaded environments, and can reduce the diversity of ground cover and prevent the establishment of tree and shrub seedlings. Because of its limited seed dispersal ability, short-lived seed bank and seedling recruitment, the primary vector for dispersal to new areas is human plantings as an ornamental, medicinal or vegetable plant, as well as by accidentally spreading rhizomes by dumping of garden waste. It spreads rapidly under favorable growing conditions.[17] Because of this it has been described as a nuisance species,[18] and been labelled one of the "worst" garden weeds in perennial flower gardens.[17]
A. podagraria has been introduced around the world, including in North America, Australia, New Zealand and Japan, most commonly as an ornamental plant. It readily establishes and can become naturalized in boreal, moist-temperate and moist-subtropical climates. It is an aggressive invader in the upper Great Lakes region and northeastern North America, Australia, Tasmania and New Zealand.[14] It can pose an ecological threat owing to its invasive nature, with potential to crowd out native species.[3] Because of its potential impacts on native communities and the difficulty of controlling it, it has been banned or restricted in some jurisdictions outside its native range, including in Connecticut, Massachusetts, Wisconsin and Vermont in the USA.[13]
Once established, goutweed is difficult to eradicate. The smallest piece of rhizome left in the ground will quickly form a sturdy new plant. All-green goutweed may be more persistent and spread more rapidly than ornamental, variegated goutweed varieties, making the all-green type particularly difficult to control. And all-green, wild type forms are known to reappear from seeds of variegated varieties.
Integrative management strategies that combine herbicide with landscape cloth, bark mulch, and hand weeding to control goutweed in a garden are largely unsuccessful because sprouting occurs from either rhizomes or root fragments left in the soil.[19] Hand pulling, raking, and digging followed by monitoring to control goutweed may be effective; however, caution must be taken to remove the entire rhizome and root system. Removing flowers before seed set may help control the spread of goutweed.[20] Because goutweed's starch reserves are typically depleted by spring, removal of leaves in spring could be effective in starving the plant. Once goutweed has been removed, the patch should be carefully monitored periodically for a few years. New shoots should be dug up and destroyed. Revegetation with other plant materials is recommended.
Systemic herbicides such as glyphosate are recommended because A. podagraria will regrow if merely defoliated.[21][22]
The most effective means of control is to prevent its establishment in natural communities. It is thus recommended to plant goutweed only on sites not adjacent to wildlands and in gardens where root spread can be restricted (e.g., between a sidewalk and a house).[18] However, the aggressive nature of this plant makes even this strategy risky. Several states have banned sales of goutweed (also known as bishop's weed).[23]
A variegated form is grown as an ornamental plant. However it is banned in several states owing to its invasiveness. Seeds from the variegated form may revert to the more aggressive green form.[23]
In Eurasia, it is used as a food plant by the larvae of some species of Lepidoptera, including dot moth, grey dagger and grey pug, although A. podagraria is not the exclusive host to any of these species.
The tender leaves have been used since antiquity as a spring leaf vegetable, much as spinach is used. It is commonly used for soup. Young leaves are preferred as a pot herb. It is best picked from when it appears (as early as February in the UK and other parts of northern Europe) to just before it flowers (May to June). If it is picked after this point it tastes pungent and has a laxative effect. However it can be stopped from flowering by pinching out the flowers, ensuring the plant remains edible if used more sparingly as a pot herb.[24]
It also had a history as a medicinal herb to treat gout and arthritis,[25] applied in hot wraps externally upon boiling both leaves and roots together. Ingested, the leaves have a diuretic effect and act as a mild sedative. Its use as a medicinal herb has largely declined.
The plant is said to have been introduced into Great Britain by the Romans as a food plant and into Northern Europe as a medicinal herb by monks. It is still found growing in patches surrounding many monastic ruins in Europe, and descriptions of its use are found among monastic writings, such as in Physica by Hildegard von Bingen.
Do not confuse with extremely toxic poison hemlock and hemlock water-dropwort.
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ground elder
Flowerhead from above, each secondary umbel (umbellet) with 15 to 20 rays
Basal leaf
Entire plant
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Spreading habit
Triangular stem profile
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{{cite web}}: CS1 maint: bot: original URL status unknown (link) Aegopodium podagraria, commonly called ground elder, is a species of flowering plant in the carrot family Apiaceae that grows in shady places. The name "ground elder" comes from the superficial similarity of its leaves and flowers to those of elder (Sambucus), which is not closely related. Other common names include herb gerard, bishop's weed, goutweed, gout wort, snow-in-the-mountain, English masterwort and wild masterwort. It is the type species of the genus Aegopodium. It is native to Europe and Asia, but has been introduced around the world as an ornamental plant, where it occasionally poses an ecological threat as an invasive exotic plant.
