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Species
Fallopia sachalinensis (F. Schmidt) Ronse Decraene (1988)
IUCN
NCBI
EOL Text
More info for the terms: avoidance, rhizome
Site description: Giant knotweed establishes in disturbed areas [42,78], including railroads [142], roadsides [78,142], and old homesites [142]. In Pennsylvania, giant knotweed established on abandoned fill and gravel and sand roadway materials [87]. A field guide reported that giant knotweed is likely to establish along streams or streambanks and in forests or woodlands of the Upper Midwest [28].
Japanese knotweed commonly establishes in disturbed areas ([53,65,78,83,98,114], review by [102]), including roadsides [8,32,40,51,56,73,78,98,114,142], along railroad tracks [6,56,74], in gravel pits, dumps [142], vacant lots [56,83], pastures [56], and abandoned fields [83] or gardens [51,56,83]. Japanese knotweed also occurs in woodland thickets [56] and borders [9], edge habitats [41], ravines [65], early successional forests, wetlands, wet meadows [83], floodplain forests [83,114], and the margins of ponds and lakes [114]. One source reports Japanese knotweed spreading from roadsides into adjacent forests in New York [73].
Descriptions of characteristics of sites with Bohemian knotweed are lacking in the literature (2010). One source reports it escaping cultivation and establishing on riverbanks, roadsides, garden dumps, and disturbed ground in western Washington [153].
Elevation: There is little information regarding the elevational limits of the 3 knotweeds in North America (2010). One flora reports that giant knotweed occurs from 0 to 1,800 feet (0-550 m) in North America [42]. Japanese knotweed was reported from 4,000 to 6,000 feet (1,220-1,830 m) in Utah [147] and at "low" elevations in Colorado [146]. In Japan, the upper elevation limit of Japanese knotweed is approximately 8,200 feet (2,500 m), with seedling survival decreasing as elevation increases [80].
Climate: The 3 knotweeds encounter a variety of climates throughout their North American distribution. In Washington where all 3 knotweeds occur, the average monthly maximum and minimum temperatures are 60 °F (15 °C) (August) and 40 °F (5 °C) (January). Annual precipitation averages 72 inches (1,820 mm), of which 27 inches (680 mm) falls as snow [136]. In the United States, Japanese knotweed appears to be established in all areas with more than 20 inches (>500 mm) mean annual precipitation (review by [102]).
Several sources suggest that the 3 knotweeds are limited by climate or weather events ([74,87], reviews by [7,11]). Aboveground shoots are highly susceptible to both late spring and early autumn frosts, which cause leaf drop, while the rhizome systems are able to survive in frozen soils. Early spring frosts often cause dieback, followed by regeneration from rhizomes (review by [7]). Short growing seasons and frosts that damage rhizomes also limit the ability of Japanese knotweed plants to store reserves for winter survival (review by [11]). However, one source reports that Japanese knotweed rhizome fragments dug from the ground and left out over winter were still able to regenerate [25]. At field experiment sites in Pennsylvania, giant knotweed seedlings not protected by experimental light barriers experienced early frost damage, while those under light barriers grew into October [87]. In Japan, Japanese knotweed seedlings with a dry weight of <10 mg were unable to survive a winter at either 4,600 feet (1,400 m) or 8,200 feet (2,500 m); seedlings exhibited 100% overwinter survival when dry weight was ≥40 mg. Survival was higher at 4,600 feet (1,400 m) where growing seasons were longer and winter temperatures were higher than at 8,200 feet (2,500 m) [80]. In the United Kingdom, Japanese knotweed plants were vulnerable to spring winds that damaged undeveloped leaves (review by [11]).
Some sources predict an expansion in the range of Japanese knotweed in Europe with the increasing temperatures expected from global climate change (review by [7]). Reports of recent high seed production by the 3 knotweeds in Europe could be partially due to warmer climate; as a late-season flowerer, seed production is reportedly limited by early-season frosts [3]. For information on how climate change might increase the invasiveness of Japanese knotweed in the United Kingdom see [10].
In North America, results from a Massachusetts study suggest that warming climates may allow additional Japanese knotweed seedling survival in places where cold temperatures currently limit survival. However, shade was found to be more limiting to seedling survival than climate in this study [44].
Soils: Japanese (reviews by [11,102]) and giant knotweed (review by [118]) are not limited by soil type. In its native range, Japanese knotweed commonly occurs on basaltic gravels [80]. In New Jersey, Japanese knotweed was found on sites with a range of soil textures, including silt, silt loam, and beach sand [74]. In the central Cascades of Washington, Japanese knotweed established on gravelly sandy loam [40]. Near Washington, DC, Japanese knotweed occurred on sandy loam, sand, and loamy sand [104].
Little information is available on soil nutrient preferences of the 3 knotweeds (2010). Japanese knotweed tolerated a range of soil nutrient levels in New Jersey [74]. In United Kingdom, Japanese knotweed established on relatively nutrient-rich soils (review by [11]).
Japanese knotweed can tolerate low soil pH; it is not clear if this pattern applies to giant or Bohemian knotweed. A guide for revegetating minespoils reports that Japanese knotweed tolerates extremely acidic soil, with a lower pH limit of 3.5 [141]. It grew in a range of soil pH in New Jersey (4.5 to 7.4) and was not limited by pH in the United Kingdom (review by [11]). Japanese knotweed had high survival (80%) 4 growing seasons after planting on acid surface-mine spoils in eastern Kentucky [91]. The Russian Agricultural Ministry suggests the avoidance of acidic soils when planting giant knotweed (review by [118]).
On Long Island, New York, Japanese and Bohemian knotweed have established in salt marshes. Greenhouse experiments demonstrated that individual plants varied in their response to different levels of salt exposure, suggesting that salt tolerance is not genetically predetermined but is determined by exposure [97]. In New Jersey it was noted that Japanese knotweed tolerated salt spray from the ocean [74].
The prevalence of the 3 knotweeds in riparian areas suggests tolerance of high soil moisture. Most herbarium specimens from North America documented Japanese knotweed in locations with high soil moisture (review by [7]). In New Jersey, Japanese knotweed often established near streams where soils were likely saturated with water through a majority of the growing season [74]. In New York, Japanese knotweed occurred on both dry and moist ruderal sites [35]. The occurrence of Japanese knotweed on dry ruderal sites suggests an ability to tolerate low soil moisture, though one study attributed slow seedling growth to dry local conditions [44]. The Russian Agricultural Ministry suggested avoiding excessively damp soils when planting giant knotweed (review by [118]). In the Czech Republic, it was reported that giant knotweed prefers sites with plenty of water [79].
As of 2010, there was very little information related to seed banking of the 3 knotweeds. All available information was related to seed longevity of wild-collected Japanese knotweed seeds. Japanese knotweed seeds from Massachusetts retained up to 100% viability for 4 to 16 months after indoor storage [44], while those from New Jersey rarely germinated after 1 year of storage [74]. In established stands of Japanese knotweed in Pennsylvania, the emergence of high numbers of Japanese knotweed seedlings suggested seedlings originated from the soil seed bank [16]. See Germination for more details of this study.
Disturbed places; 0-500m.
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Rights holder/Author | eFloras.org Copyright © Missouri Botanical Garden |
Source | http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=250060605 |
Though seed production of the 3 knotweeds has been documented in North America, it is not clear how representative this information is for all populations. Even if seeds are produced, they may or may not be viable. In the Pacific Northwest, the seeds of giant and Japanese knotweed were largely infertile while Bohemian knotweed seeds were viable [115]. In New Jersey, Japanese knotweed populations produced seeds but they were not viable [74]. One review reports that though giant knotweed produces seeds, seeds do not mature in temperate zones [118].
In areas with all 3 knotweeds in Pennsylvania, single stems produced 50,000 to 150,000 seeds annually; millions of seeds were produced over a 108-ft² (10-m²) area in some locations [87]. Based on field observations in Pennsylvania, 1 Japanese knotweed stem was capable of producing over 127,000 seeds/year if all flowers were pollinated and seeds set. Consequently, a single seed-bearing plant with 10 stems/plant would be capable of producing more than a million seeds/year [16]. Giant knotweed seedlings from 2 field locations in Pennsylvania produced both flowers and seeds within 3 months of emergence [87].
In Great Britain and/or Ireland:
Foodplant / saprobe
scattered, subepidermal, piercing pycnidium of Amphorula coelomycetous anamorph of Amphorula sachalinensis is saprobic on dead stem of Fallopia sachalinensis
Foodplant / saprobe
sclerotium-like pycnidium of Chaetoconis coelomycetous anamorph of Ceriospora polygonacearum is saprobic on dead stem of Fallopia sachalinensis
Remarks: season: 3-4
Foodplant / saprobe
immersed, loosely gregarious pycnidium of Phomopsis coelomycetous anamorph of Phomopsis polygonorum is saprobic on dead, epidermis blackened stem of Fallopia sachalinensis
Remarks: season: 5-8
More info on this topic.
More info for the terms: phenology, rhizome
In North America, giant knotweed flowers from July to October [42], with some regional variation [78,85,94,121,150]. In North and South Carolina, giant knotweed produces fruit from August to October [94]. In Pennsylvania, seeds are mature in September [87]. Giant knotweed overwinters via an underground woody rhizome (review by [7]). In the Pacific Northwest, giant knotweed growth begins in April and stems may grow 15 feet (4.5 m) by June [115].
Japanese knotweed flowers from June through August in Pennsylvania [16]; August to September in Illinois [85], the Great Plains [51], and New England [78]; and August to October in Kentucky [56]. In Pennsylvania, Japanese knotweed fruit begins to form in late August [16] and matures in September [87]. In the eastern United States, fruits generally remain on plants through the winter. Leaves are photosynthetically active until autumn frosts prompt senescence. Leaves drop throughout the winter months. Assimilation of resources shifts from shoots to roots near the end of the growing season, as the plant prepares for overwintering (review by [7]). Near Washington, DC, Japanese knotweed plants allocated most resources to aboveground growth until approximately 30 July. Through most of August, resources were allocated equally to both aboveground and belowground parts. After 28 August, most resources were allocated to belowground parts [103]. In the eastern United States, Japanese knotweed seedlings emerge in mid-spring (late March to May) depending on latitude and altitude. Rhizome sprouts emerge from late spring through mid-summer until the canopy closes (review by [7]).
As of this writing (2010) little information is available regarding the phenology of Bohemian knotweed. In the Pacific Northwest, Bohemian knotweed growth begins in April [115]. It probably flowers in the late summer and early fall like giant and Japanese knotweed, because seeds of all 3 species were mature in September in Pennsylvania [87]. Bohemian knotweed overwinters via an underground, woody rhizome (review by [7]).
More info for the term: fire regime
It is not known what type of fire regime the 3 knotweeds are best adapted to. They are common in riparian areas in many parts of North America, and FIRE REGIMES in riparian areas are often related to the FIRE REGIMES of adjacent upland communities. Thus FIRE REGIMES for plant communities with the 3 knotweeds could be quite variable. See the Fire Regime Table for further information on FIRE REGIMES of vegetation communities in which the 3 knotweeds may occur.
Flowering Jul-Oct.
License | http://creativecommons.org/licenses/by-nc-sa/3.0/ |
Rights holder/Author | eFloras.org Copyright © Missouri Botanical Garden |
Source | http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=250060605 |
More info for the terms: cover, fuel, fuel loading, litter, tree
It is not clear whether occurrence of the 3 knotweeds changes the fuel characteristics of invaded plant communities. Fuel characteristics of plant communities could potentially be altered in areas where the 3 knotweeds exhibit fuels traits (e.g., flammability, fuel loading, plant architecture), densities, and/or growth patterns differing from those of native vegetation.
Laboratory analyses suggest that Japanese knotweed foliage and stems are not particularly flammable [33]. Giant knotweed appears to exhibit similar characteristics. In the Czech Republic, the water content of spring giant knotweed stems reached values as high as 1,800% of dry mass. After 2 months, stem water content decreased and matched that of leaves, at 400% of dry mass [79]. In Russia, giant knotweed stems and leaves reportedly had an 82% moisture content. Consequently, Russian forestry officials investigated the use of 7-foot-tall stands of giant knotweed (referred to as Sakhalin buckwheat) as a live fire break to protect tree plantations. The testing occurred on a hot, dry day with a mild south wind. "The reaction of Sakhalin buckwheat thicket to forest fire was tested by igniting a brush fire in the wind direction 7 feet from the thicket edge. The incendiary fuel was brushwood, pine branches, drenched copiously with kerosene. Set ablaze on the buckwheat thicket side of the plantation, the brush fire whipped by wind burned fiercely for 30 minutes. The test established that buckwheat thickets minimize the effect of fire and at 8-inch depth localize it. The fire does not spread across the thicket to the tree plantation growing on the other side of the protective green zone. The zone itself suffers little from the effect of fire. Only 10% of the foliage embraced in flames, was curled up from burning. The thicket continued to stand upright. The commission concluded that thickets of Sakhalin buckwheat are a completely effective barrier against low forest fires and can be recommended for planting in fireproof zones and banks" (Russian Agricultural Ministry cited in [118]).
As of this writing (2010) no studies have documented fuel characteristics of litter of the 3 knotweeds. Litter accumulations can be high in some stands. In old fields in south-central New York, litter depth was higher in Japanese knotweed stands compared to outside the stands, though the litter material was almost all large, fibrous stems (P<0.05) [77]. In Pennsylvania it was noted that dense litter built up every autumn under riparian stands composed of all 3 knotweeds, though litter was generally washed away by summer [87]. In riparian forests of northwestern Washington, total mass of autumn litterfall did not differ between plots with and without established giant knotweed, though litter composition varied [136].
Occurrence of the 3 knotweeds may result in changes in aboveground vegetative structure that could impact fuel characteristics. Changes in vegetative architecture were observed in old fields in south-central New York. Vegetation height increased abruptly at the edge of Japanese knotweed stands, and average height of the first leaf was higher in Japanese knotweed stands compared to outside of stands [77]. In Belgium, plots with Japanese knotweed had higher aboveground biomass compared to plots with native vegetation (2.95 vs. 0.56 kg/m²) [29,30]. The 3 knotweeds often cover extensive areas [31,44,53,61,103,107,116,125] and may dominate local vegetation ([73,87], review by [118]) (see Plant growth).