204 THE GREAT LAKES BOTANIST Vol. 56

NOTEWORTHY COLLECTION PARVIFLORA DC. (): FIRST RECORD FROM WISCONSIN AND THE GREAT LAKES REGION OF A POTENTIALLY INVASIVE

Joseph R. Rohrer Department of Biology University of Wisconsin-Eau Claire Eau Claire, WI 54702-4004 [email protected]

Previous Knowledge . (small balsam, small-flowered touch-me-not) is an annual herb native to central Asia. It became established in in the mid-19 th century, and today is a common and widespread invasive throughout eastern, central, and northern Europe (Chmura & Sierka 2006, Hejda 2012). Reczyn så ka et al. (2015) called it “the most commonly observed alien plant in Central European deciduous forests.” The Database (USDA-NRCS 2016) does not list Impatiens parvi - flora for any U.S. state, but includes it for the Canadian provinces of British Co - lumbia, New Brunswick, Nova Scotia, Prince Edward Island, and Quebec. In 2013 thousands of plants were discovered in the understory of a mesic forest in Oregon (D. Maze s.n., July 8, 2013, OSC#241051; P.F. Zika 26231 & D. Maze, July 19, 2013, OSC#241857). As of this writing, North American observations of Impatiens parviflora have been posted on the citizen science website iNatu - ralist (2016) from Prince Edward Island, the Vancouver area of British Colum - bia, the Seattle area of Washington, and the Portland area of Oregon, as well as my observation from Eau Claire, Wisconsin. Discussion . Impatiens parviflora was introduced to botanic gardens in Eu - rope beginning about 1830 (Coombe 1956). Coombe speculated that the spread of the species across Europe was probably due to a single introduction of seed, because the European populations are very uniform in contrast to the polymor - phism exhibited by populations in the species’ native mountains of Asia. Whether or not this is true, the species has proven itself to be an extremely suc - cessful invader and has proved highly adaptable in Europe over time. Today it is common in moist deciduous forests, particularly those with some degree of dis - turbance and along forest edges (Chmura & Sierka 2006). It is best at colonizing areas with a sparse herb layer, but is much less successful in areas with a thick herbaceous cover (Chmura & Sierka 2006). Unlike many exotics, it has also suc - cessfully invaded undisturbed forest (EPPO 2016). Impatiens parviflora shows high ecological plasticity in its ability to inhabit soils of varying acidity, fertility, and moisture ( Reczyn så ka et al. 2015), although it is intolerant of waterlogged soils (Coombe 1956). Although it was previously absent from central European oak forests, it began establishing itself in those habitats in the 1960s and now is 2017 THE GREAT LAKES BOTANIST 205

FIGURE 1. Dense cover of Impatiens parviflora on the campus of the University of Wisconsin-Eau Claire in Eau Claire, Wisconsin. Photo by Joseph R. Rohrer. found in over 20% of vegetation sampling plots ( Reczyn så ka et al. 2015). Mean cover of I. parviflora in those plots, however, has not increased in the past 30 years. The authors concluded that the presence of I. parviflora has not had a se - rious effect on oak forests and that, despite its invasion of a new community type, this weed has a low competitive ability and rarely becomes dominant (Reczyn så ka et al. 2015). Plant removal experiments have shown that the impact of I. parviflora on diversity and composition of the herb layer of forest commu - nities was minimal (Hejda 2012). The Eau Claire site is a highly disturbed remnant of floodplain forest on the University of Wisconsin-Eau Claire campus between Haas Fine Arts building and the Chippewa River to the south. Canopy species are a mix of native and or - namental species, some planted and others naturalized: Acer negundo L., A. pla - tanoides L., A. saccharinum L., Celtis occidentalis L., Fraxinus pennsylvanica Marshall, Gymnocladus dioicus (L.) Koch, Morus alba L., Juglans nigra L., Populus deltoides Marshall, Robinia pseudoacacia L., and Ulmus rubra Muhl. The shrub layer consists of saplings of a majority of the canopy species, the na - tive shrub Sambucus racemosa L., and two invasive exotics, Lonicera ×bella Zabel and Rhamnus cathartica L. Ageratina altissima (L.) R. M. King & H. Rob. is the most common herb species found with Impatiens parviflora . Other com - mon co-occurring herbs include Erigeron annuus (L.) Pers., Geum canadense 206 THE GREAT LAKES BOTANIST Vol. 56

FIGURE 2. Flowers of Impatiens parviflora. Photo by Joseph R. Rohrer.

Jacq., Hesperis matronalis L., Leonurus cardiaca L., Nepeta cataria L., Parthenocissus inserta (A. Kern.) Fritsch, and L. In July 2016 thousands of individuals of Impatiens parviflora were growing in deep shade on the slope just south of the Fine Arts building (Figure 1) and continuing westward for about 240 meters in moderate shade along the edge of a narrow forest rem - nant and mowed lawn to the north. What is the potential for Impatiens parviflora to become a pernicious weed in the Great Lakes region, or elsewhere in the United States? Recently the USDA Plant Epidemiology and Risk Analysis Laboratory of the Animal and Health In - spection Service (APHIS 2013) published a weed risk assessment for Impatiens parviflora concluding that it posed a high risk. Comparing it to the other species using the weed risk assessment model of Koop et al. (2012), I. parviflora shared many of the traits of other invasive species (APHIS 2013). However, when com - pared to species with similar establishment/spread risk scores, the impact score for I. parviflora was relatively low. If it follows the pattern of invasion seen in Europe, it may become widespread but have only minimal impact on forest herb diversity. Diagnostic Characters. As its name suggests, Impatiens parviflora can be distinguished from other exotic Impatiens and our two native species, I. capensis Meerb. and I. pallida Nutt., by its small flowers that measure only 0.8 –1.5 cm in length. The flowers of I. parviflora are pale yellow with some reddish brown spotting at the throat. In contrast the exotics are various shades of red, purple, blue, or white, and I. capensis is orange. Only I. pallida has a color similar enough to be confused with I. parviflora , but the flowers are decidedly larger, at least 2.5 cm in length. In I. pallida the spur is bent at a right angle to the axis of the saccate sepal, whereas in I. parviflora the spur is straight (Figure 2). Leaf blades of I. parviflora have sharp teeth, averaging about 3 teeth per cm along the 2017 THE GREAT LAKES BOTANIST 207 margin; I. pallida has blunt teeth that are more remotely spaced with only 1-2 per cm. Specimen Citation. Wisconsin, Eau Claire Co., City of Eau Claire, campus of the University of Wisconsin-Eau Claire, between Haas Fine Arts Bldg. on Water St. and the Chippewa River (N44.800631, W91.502274; elev. 238 meters). Carpeting shaded forest floor in highly disturbed remnant of floodplain forest. July 2, 2016, Joseph R. Rohrer 10892 (UWEC; WIS, MICH, WTU); August 8, 2016, Joseph R. Rohrer 10893 (UWEC).

LITERATURE CITED APHIS. (2013). Weed risk assessment for Impatiens parviflora DC. (Balsaminaceae)—Smallflower touch-me-not, small balsam. Version 1 (September 24, 2013) United States Department of Agri - culture, Animal and Plant Health Inspection Service (APHIS). Available at https://www.aphis. usda.gov/plant_health/plant_pest_info/weeds/downloads/wra/Impatiens_parviflora_WRA.pdf. (Accessed August 9, 2016). Chmura, D. and E. Sierka. (2006). Relation between invasive plant and species richness of forest floor vegetation: A study of Impatiens parviflora DC. Polish Journal of Ecology 54: 417-428. Coombe, D. E. (1956). Biological flora of the British Isles: Impatiens parviflora DC. Journal of Ecol - ogy 44: 701 –713. EPPO. (2016). EPPO data sheet on invasive plants: Impatiens parviflora (05-11832, P IAS point 7.2). European and Mediterranean Plant Protective Organization. Available at http://www.eppo.int/ QUARANTINE/Pest_Risk_Analysis/PRAdocs_plants/draftds/05-11832%20DS%20Impatiens %20parviflora.doc. (Accessed August 9, 2016). Hejda, M. (2012). What is the impact of Impatiens parviflora on diversity and composition of herbal layer communities of temperate forests? PLoS ONE 7(6): e39571. Available at http://journals. plos.org/plosone/article?id=10.1371/journal.pone.0039571 . (Accessed August 9, 2016). iNaturalist. (2016). Available at http://www.inaturalist.org. (Accessed August 9, 2016). Koop, A. L., L. Fowler, L. P. Newton, and B. P. Caton. (2012). Development and validation of a weed screening tool for the United States. Biological Invasions 14: 273-294. Reczyn så ka , K., K. S wÅ ierkosz, and Z. Dajdok. (2015). The spread of Impatiens parviflora DC. in cen - tral European oak forest—another stage of invasion? Acta Societas Botanicorum Poloniae 84: 401 –411. USDA NRCS. (2016). The PLANTS Database. National Plant Data Team, Greensboro, North Car - olina. Available at http://plants.usda.gov. (Accessed August 9, 2016).