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  This content is marked PUBLIC by 2023-2024 Western IPM Project

Impatiens glandulifera -- California

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Created by: Jutta Burger
Created on: Friday, Sep 22nd, 2023
Evaluation Summary
Impatiens glandulifera (Himalayan balsam) is a succulent annual that is native to the Himalayas and introduced into many other temperate regions. It was introduced into Europe and likely North America as an ornamental but has naturalized and spread quickly since then on its own across much of its introduced range. Long-distance dispersal is primarily via waterways and contaminated materials. This species grows quickly and competes primarily with other taller understory riparian plant species, displacing them over time. Its rapid spread and effect on native understory cover contribute to its assessment as a a high risk for future invasion.
General Evaluation Information
Date of Evaluation: 
September 22, 2023
Evaluation Time (hrs): 
Not Recorded
Evaluation Status: 
Completed
Plant Information
Plant: 
Impatiens glandulifera
Plant Material: 
If the plant is a cultivar, and if the cultivar's behavior differs from its parent's (behavior), explain how: 
Regional Information
Region Name: 
California
Climate Matching Map
These maps were built using a toolkit created in collaboration between GreenInfo Network, PlantRight, Cal-IPC, and Agricultural Sustainability Institute at UC Davis.
PRE Climate Map (external link)
Climate Matching Maps PDF: 
AttachmentSize
PDF icon ClimateMatch-Impatiens_glandulifera-California-20230922.pdf1.22 MB
Invasive History and Climate Matching
1. Has the species (or cultivar or variety, if applicable; applies to subsequent "species" questions) become naturalized where it is not native?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
Impatiens glandulifera (Balsaminaceae) is a tall summer annual that is native to the foothills of the Himalayas in India and Pakistan. Several detailed studies have tracked its expansion outside of its range (e.g., Beerling and Perrins, 1993; Pysak and Prach 1995). It has become widely naturalized in moist habitats across Europe, Siberia, New Zealand, South America (Colombia and Chile), and North America, where it has been introduced deliberately as an ornamental. In Europe, it was first introduced as an ornamental 1839 and reported as naturalized in 1855. It is now the most common non-native plant in riparian systems in the UK (Tanner et al. 2014). It was first collected in Marin Co., California where it was recorded as naturalized in 1970 (CDFA herbarium record in Calflora). Impatiens glandulifera can also establish in waste places and other moist, disturbed sites away from riparian habitat.
Reference(s): 
2. Is the species (or cultivar or variety) noted as being naturalized in the US or world in a similar climate?
Yes or No: 
Yes
Points: 
2
Confidence Level: 
High
Answer / Justification: 
Impatiens glandulifera has been documented as naturalizing in a limited number of areas that are similar to more mesic regions of California, including California, parts of southern Europe (including Spain), Oregon, and parts of New Zealand (Randall 2017, GBIF 2023). In California, Impatiens glandulifera was first recorded near Tomales Bay, Marin County, by CDFA in 1970 (Calflora 2023). As of 2023, apparently naturalized populations have been reported in Calaveras, Del Norte, Marin, and Mendocino County (Calflora 2023, iNaturalist 2023).
Reference(s): 
3. Is the species (or cultivar or variety) noted as being invasive in the U.S. or world?
Yes or No: 
Yes
Points: 
2
Confidence Level: 
Very High
Answer / Justification: 
Impatiens glandulifera is considered invasive across much of Europe, where it ranks among the region's worst weeds. It is also listed as invasive or on Watch Lists for Connecticut, Idaho, Maine, Michigan, Oregon, Washington, Wisconsin, as well as in Canada.
Reference(s): 
4. Is the species (or cultivar or variety) noted as being invasive in the US or world in a similar climate?
Yes or No: 
Yes
Points: 
3
Confidence Level: 
High
Answer / Justification: 
Impatiens glandulifera is "B" listed as a noxious weed in Oregon, which partially matches California's climate. The areas where Impatiens glandulifera is highly invasive appear to generally be wetter and more temperate than those found across most of California, yet the species has clearly established in parts of California that meet those criteria. Beerling and Perrins (1993) report that its distribution is largely dictated by the presence of mesic seasonal temperature and limited by severe frost.
Reference(s): 
5. Are other species of the same genus (or closely related genera) invasive in a similar climate?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Medium
Answer / Justification: 
Impatiens balfourii, also native to the Himalayas, is considered invasive to a limited degree in the alpine foothills of Europe, some of which overlap in climate with California. Impatiens capensis, a native to eastern N. America, is naturalized in the Pacific Northwest and some parts of Europe in areas with some climate overlap with California. It has also been recorded in Southern California, Bay area and Santa Cruz, though is of unknown invasiveness there.
Reference(s): 
6. Is the species (or cultivar or variety) found predominately in a climate matching the region of concern?
Yes or No: 
No
Points: 
0
Confidence Level: 
Very High
Answer / Justification: 
Numerous publications and databases describe the extensive range expansion of Impatiens glandulifera into temperate regions that are dissimilar to California's climate (e.g., Pysek and Prach 1995, Clements et al., 2008). Climate Match tool results and GBIF (2023) show that most of the introduced range of the species is in across northern Europe, Siberia, and eastern North America, and does not match California's climate.
Reference(s): 
Impact on Native Plants and Animals
7. Does this plant displace native plants and dominate (overtop or smother) the plant community in areas where it has established?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
High
Answer / Justification: 
Impatiens glandulifera has been reported to displace native cover in riparian habitat across its introduced range in Europe (Hulme and Bremner 2006, Bruntmann et al. 2014, Coakley and Petty 2021). Its impacts are especially severe when it reaches a high cover. In highly invaded habitat, it can altern soil mycorrhizal communities and may impact native seedling recruitment through allelopathy (Gruntman et al., 2014). Impatiens glandulifera is the tallest recorded annual that occurs now in Europe, reaching heights of up to 2m in a single season. Its rapid growth, tall stature, and leafy habit enable it to overtop other species quickly. In an experimental field trial, I. glandulifera was able to successfully outcompete an otherwise vigorous native competitor, Urtica dioica (Gruntman et al., 2014). However, Hejda and Pysek (2006) found that I. glandulifera did not have a significant and lasting effect on native diversity in riparian habitat, in contrast to other invasives, such as Fallopia japonica and Heracleum mantegazzianum. Their study did suggest that I. glandulifera replaced other tall nitrophilous species, such as Urtica and Chenopodium. Impatiens glandulifera is presumed to have a less severe impact on native flora than other rhizomatous riparian invaders because of its annual nature and variable stand size across years (Coakley and Petty 2021).
Reference(s): 
8. Is the plant noted as promoting fire and/or changing fire regimes?
Yes or No: 
No
Points: 
0
Confidence Level: 
Medium
Answer / Justification: 
Impatiens glandulifera is highly unlikely to change fire regimes. It grows in moist, riparian habitats (Pisak and Prach 1995). Plants are succulent annuals that are not reported to persist and leave behind fuels.
Reference(s): 
9. Is the plant a health risk to humans or animals/fish? Has the species been noted as impacting grazing systems?
Yes or No: 
No
Points: 
0
Confidence Level: 
High
Answer / Justification: 
Impatiens glandulifera is not known to be poisonous to humans or animals, though may be toxic when ingested in large quantities; it has been used as part of an herbal treatment for "emotional distress" and "irritability" (Wikipedia 2023). It can be browsed by cattle, though its browse value is unknown (CABI 2023). Impatiens glandulifera flowers produce nectar with very high sugar content and are therefore especially attractive and potentially beneficial to bees. Arthropod assemblages are altered in highly invaded sites but not necessarily negatively impacted (see Coakley and Petti 2021).
Reference(s): 
10. Does the plant produce impenetrable thickets, blocking or slowing movement of animals, livestock, or humans?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Medium
Answer / Justification: 
Despite its annual nature and its loose growth form, Impatiens glandulifera, has been implicated as a species that creates thickets that persist, in part because of its tall growth habit and persistent, holocellulose-rich stems (Beerling and Perrins, 1993; Alaska Center for Conservation Science, 2011). It is can also apparently increase erosion along streambanks, impacting waterways (see CABI 2023). Confidence is "Medium" because evidence is inferential.
Reference(s): 
Reproductive Strategies
11. Does this species (or cultivar or variety) reproduce and spread vegetatively?
Yes or No: 
No
Points: 
0
Confidence Level: 
Very High
Answer / Justification: 
This plant is an annual; it does not reproduce vegetatively.
Reference(s): 
12. If naturally detached fragments from this plant are capable of producing new plants, is this a common method of reproduction for the plant?
Yes or No: 
No
Points: 
0
Confidence Level: 
Very High
Answer / Justification: 
This plant is an annual; it does not reproduce vegetatively.
Reference(s): 
13. Does the species (or cultivar or variety) commonly produce viable seed?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
Impatiens glandulifera is a self-compatible annual that reproduces solely by seed. In a field study in Poland, seed viability was found to be very high, at nearly 98% (Janczak 2013).
Reference(s): 
14. Does this plant produce copious viable seeds each year (> 1000)?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
Estimates of seed production for Impatiens glandulifera vary from 800 to up to 2500 seeds per plant and 5000-6000 / m2 (Pysek and Prach 1995, Janczak 2013).
Reference(s): 
15. Is there significant germination (>25%) of seeds the next growing season, with no requirement of an infrequent environmental condition for seeds to germinate (i.e. fire) or long dormancy period?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
Several field studies have shown high viability and remarkably high germination rates in the next growing season (example 97.8% in Poland; Jancak 2013) with virtually no seeds remaining dormant in the soil seed bank. Seeds with high germination rates experienced cold winter temperatures, which are common in the environments where I. glandulifera has invaded. Flooding increases seed decay and reduces germination rates. Some earlier studies suggest soil residence time of up to three years, but Jancak 2013 was not able to verify any dormancy in the field.
Reference(s): 
16. Does this plant produce viable seed within the first three years (for an herbaceous species) to five years (for a woody species) after germination?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
Impatiens glandulifera is an annual plant that matures and reproduces withing a single growing season.
Reference(s): 
17. Does this plant continuously produce seed for >3 months each year or does seed production occur more than once a year?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
High
Answer / Justification: 
The Jepson Flora of California lists flowering time to occur from April to September (Zika 2006). According to NOAA's Great Lakes Aquatics Non-indigenous Information System, Impatiens glandulifera can flower from June through October or the first frost (Cao et al., 2023). Research study measured flowering only over the course of approximately two months (Willis and Hulme 2004), but probably truncated the flowering time that it evaluated.
Reference(s): 
Dispersal
18. Are the plant’s propagules frequently dispersed long distance (>100 m) by mammals or birds or via domestic animals?
Yes or No: 
No
Points: 
0
Confidence Level: 
Low
Answer / Justification: 
Distribution patterns of seedlings at distances over 10m relative to mother plants suggest that small mammals may be moving seed (Beerling and Perrins 1993), but direct evidence is lacking that animals are moving seed across distances over 100m. Seeds can be dispersed explosively from capsules up to a distance of 7m. Canada's Invasive Species Center mentions that seeds of Impatiens glandulifera can disperse "both naturally through wind and animal dispersal" but provides no references to support their statement.
Reference(s): 
19. Are the plant’s propagules frequently dispersed long distance (>100 m) by wind or water?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
Multiple studies report seed movement via waterways. Seeds can float, lending them to movement over longer distances by water. The riparian distribution of I. glandulifera also is consistent with movement by water.
Reference(s): 
20. Are the plant’s propagules frequently dispersed via contaminated seed (agriculture or wildflower packets), equipment, vehicles, boats or clothing/shoes?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
There is strong evidence that seed has been moved through contaminated materials and equipment (see CABI). Beerling and Perrins (1993) mention movement through contaminated topsoil. Cuda et al. (2020) mention that increased "efficiency" of dispersal through the increased use of forest equipment.
Reference(s): 
Evaluation Notes

Great Lakes Fact Sheet (Cao et al., 2023): https://nas.er.usgs.gov/queries/GreatLakes/FactSheet.aspx?Species_ID=2695, accessed 12/20/2023.

Total PRE Score

  • < 13 : Low Potential Risk
  • 13 - 15 : Moderate Potential Risk
  • > 15 : High Potential Risk

PRE Score: 
18
Number of questions answered: 
20
Screener Confidence (%): 
86.0
PRE Content Access and Privacy
Organization: 
2023-2024 Western IPM Project
California Invasive Plant Council (Cal-IPC)
PlantRight
Evaluation visibility: 
Public - accessible to all site users

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