Great hairy willow-herb, hairy willowherb, hairy willow herb, codlins and cream, European fireweed, fiddle grass

Similar species: E. angustifolium L. (fireweed, great willow-herb). E. angustifolium differs from E. hirsutum in that its leaves are longer, measuring 15-20 cm (6-8 in.), and that it does not have pubescent leaves.

Epilobium hirsutum is present and considered exotic in Colorado, Connecticut, Delaware, Illinois, Indiana, Kentucky, Maine, Maryland, Massachusetts, Michigan, New Hampshire, New Jersey, New York, Ohio, Oregon, Pennsylvania, Rhode Island, Vermont, Washington, West Virginia, Wisconsin, and the Canadian provinces of British Columbia, Ontario, and Quebec (Biota of North America Program 2011). It continues to expand westward.

Epilobium hirsutum is also capable of spreading through vegetative means. At the base of the stem are axillary bubs that produce stolons. Stolons produced below the soil develop into rhizomes that can reach up to 2 feet in length. Stolons produced above ground sprout a pseudo-rosette of leaves that, if separated, will produce an aerial shoot and develop into a new plant (State of Washington 2012). Above-ground stolons can grow up to 0.5 meters (Shamsi and Whitehead 1977) before dying back in the fall.

Epilobium hirsutum is able to survive water fluctuations (State of Washington 2012). When roots are submerged or waterlogged, rhizomes develop arenchyma tissue to enable easier exchange of oxygen between the roots and the aboveground parts of the plant (King County 2008, State of Washington 2012). Within a few days of flooding, wild E. hirsutum may grow adventitious roots and display stem hypertrophy (Etherington 1984).

In observations by Nazrul-Islam (1986), E. hirsutum grew best in calcareous waterlogged soils with a pH of 6.5, poorly in non-calcareous soil with a pH of 5.9, and died in acidic soils with a pH range of 3.8 — 4.5. When grown in a nutrient solution, this species responded best to conditions of high calcium (40 mg/liter) and low manganese (0.05 mg/liter). Epilobium hirsutum displayed toxicity symptoms when exposed to a manganese level of 5 mg/liter (Nazrul-Islam 1986).

In nature surveys of the British Isles, E. hirsutum was confined to the less iron-rich soils. Epilobium hirsutum seedlings grown in soils with iron concentrations greater than 50 mg/L showed poor growth and ill health due to blackening, flaccidity, and necrosis of roots, and ultimately died (Wheeler et al. 1985).

Summary of species impacts derived from literature review. Click on an icon to find out more...

Environmental	Beneficial

Epilobium hirsutum has a moderate environmental impact in the Great Lakes.

Realized:
Once established, great hairy willow herb can spread into neighboring undisturbed habitats, such as meadows (State of Washington 2012). Shamsi and Whitehead (1977) determined that this species can germinate and grow under conditions of low temperatures and short days; furthermore, due to its growth form and pattern of vegetative reproduction, it can rapidly exploit available space. The persistent nature of great hairy willow herb enables it to form monospecific populations that exclude other, especially native, species (Shamsi and Whitehead 1974). Dense stands of E. hirsutum impede hydrology in waterways and wetlands (King County 2008, State of Washington 2012).

A joint survey conducted by the Invasive Plant Associate of Wisconsin (IPAW) and the Great Lakes Indian Fish and Wildlife Commission (GLIFWC) found that this species has a limited distribution on ecologically vulnerable sites. In the sites where it does establish, it is a moderate competitor and has a moderate to high impact (Reinartz 2003).

Potential:
Epilobium hirsutum could be a competitive threat to native species in Ohio, including E. angustifolium (state endangered) and E. strictum (state threatened) (OHDNR 2012). A few occurrences of hybridization between E. hirsutum and E. ciliatum, a native to the Great Lakes and other parts of North America, have been found in Europe, resulting in E. x novae-civitatis (Online Atlas 2012). No such hybridization has been reported in the Great Lakes.

In Washington state, great hairy willow herb disrupts wetland food chains (State of Washington 2012).

There is little or no evidence to support that Epilobium hirsutum has significant socio-economic impacts in the Great Lakes.

There is little or no evidence to support that Epilobium hirsutum has significant beneficial effects in the Great Lakes.

Realized:
Epilobium hirsutum L. is considered a medical plant in Bulgaria (Ivancheva et al. 1992). Ethanolic extracts of E. hirsutum have antimicrobial properties (Battinelli et al. 2001). Methanolic extracts of E. hirsutum exhibited antinociceptive activity in mice. Doses of 500 mg/kg resulted in higher pain tolerance than doses of diclofenac (50 mg/kg) and morphine (5 mg/kg). Furthermore, doses of the methanolic extract (200-500 mg/kg) did not impair locomotors skills of mice (Pourmorad et al. 2007). A polyphenolic mixture of E. hirsutum (combined with a water-alcohol extract) had a significant inhibitory effect on the reproduction of influenza viruses (Ivancheva et al. 1992). A few of the polyphenols extracted—galloylglucose and monomeric and dimeric ellagitannins—are important compounds for the treatment of prostate cancer (Cristea et al. 2009). Initial experiments of alcohol extracts from E. hirsutum indicate other anti-tumor properties. Small doses of alcohol extract (1-3 mg/kg) prolonged the lifespan of mice with tumors by over 150% (Voynova et al. 1991).

Epilobium hirsutum can co-exist with Lythrum salicaria (purple loosestrife) along riparian areas created by erosion. Great hairy willow herb outcompetes and grows faster than purple loosestrife in the shorter days and colder temperatures of autumn. In the spring, this relationship is reversed, with purple loosestrife having a faster growth rate (Shamsi and Whitehead 1974, Shamsi and Whitehead 1977).

Potential:
Flavonoids (3-O-glycosides of quercetin, myricetin, and kaempferol) and a macrocircular dimeric ellagitannin oenothein D have been detected in dried fragments of E. hirsutum (Strgulc Krajšek et al. 2011). Increased intake of total flavonols is associated with a reduced risk of pancreatic cancer, with kaempferol linked to greatest reduction in risk (Nöthlings et al. 2007). In epidemiological studies, quercetin supplements reduced blood pressure in hypertensive rodents. Quercetin is thought to be linked with lowering the risk of coronary heart disease and/or stroke (Edwards et al. 2007).

Great hairy willow herb is ranked as having “moderate environmental invasiveness” by the New York State Office of Invasive Species and is considered “well-established” by the Ohio Department of Natural Resources (New York 2010, Ohio Division and Nature Conservancy 2000). The transportation, translocation, or introduction of E. hirsutum is prohibited in Wisconsin, except in Kenosha County (Burea of Plant Industry 2012). Epilobium hirsutum is listed as an introduced species in Ontario (Canadensys 2012). Regionally, the Great Lakes Indian Fish & Wildlife Commission (GLIFWC) classifies this species as capable of causing moderate to severe ecological impacts and/or having limited effective control options available.

Note: Check federal, state/provincial, and local regulations for the most up-to-date information.

Control
Given the invasive nature of E. hirsutum, control methods need to be applied and monitored for several years to be effective (King County 2008). For localized infestations, the GLIFWC recommends E. hirsutum “be controlled immediately upon detection before it becomes established and spreads” (Falck and Garske 2003).

Biological
Elephant moth (Deilephila elpenor) feeds on Epilobium, but is not a native to the Great Lakes (Hoskins 2012, Pittaway 2012). Genetic material extracted from E. hirsutum individuals displaying phyllody of flowers and/or plant yellowing revealed infection by epilobium phyllody (EpPh) phytoplasma, an obligate, parasitic bacteria that attach to phloem tissue (Alminaite et al. 2002). The ability of this phytoplasma to act as a biocontrol agent is still unknown. Additional insects that feed on and/or use E. hirsutum for part of their life cycle are listed on the website of J. Lindsey (http://www.commanster.eu/commanster/Plants/Flowers/SuFlowers/Epilobium.hirsutum.html).

Physical
Small populations of E. hirsutum can be hand-dug, placed into plastic bags, and disposed of in the trash (King County 2008). When hand-digging, one should be sure to remove as many of the root pieces as possible because rhizomes left in the soil can generate new plants (Campbell et al. 2010, King County 2008). Mowing or cutting of mature plants will not kill the plant, but flowering stems can be cut in late summer or early fall to prevent seed production and dispersal (King County 2008).

After 18 weeks in waterlogged and flooded conditions, Lenseen et al. (2000) found E. hirsutum populations only achieved 82% and 54%, respectively, of the mean biomass growth as populations in drained conditions. Furthermore, it was determined that flooded individuals experienced reduced rhizomal growth in terms of numbers, size, and biomass (Lenssen et al. 2000). Growth of waterlogged plants was further limited by pruning adventitious roots. This procedure reduced the depth of the plant’s primary root system and made individuals more susceptible to uprooting by various environmental conditions (flooding, wind, etc.) (Etherington 1984). Both of these experimental insights suggest that combined water level manipulation and root pruning may be beneficial to the control of E. hirsutum.

Due to the regenerative nature of rhizomes, composting plant material off-site is not recommended (King County 2008).

Chemical
Epilobium hirsutum populations treated with Patron 170 are typically susceptible to severe injury or death. It should be noted that this pesticide is currently prohibited by from use on Forest Stewardship Council (FSC) land (WIDNR 2011). Under dry conditions, 2,4-D will control great hairy willow-herb (Evans et al. 2003). In moist or aquatic locations, glyphosate will stress or kill above-ground portions of the plant, but the root system will remain intact and plants will recover (Evans et al. 2003).

Note: Check state/provincial and local regulations for the most up-to-date information regarding permits for herbicide use. Follow all label directions.