Impatiens is a large genus of 900 or more species (many new species have been described in the past years). Most are native in tropical and subtropical areas of Africa and Asia. Species diversity is largest in China; molecular studies demonstrated that the genus originates there. However, many species occur in more temperate regions of eastern Asia as well and some also in Europe and North America. Only one species, Impatiens noli-tangere L., is a native species in Belgium (Lambinon & al. 2004). It is rare but locally more common
About 20 species are cultivated as ornamentals in Europe (Grey-Wilson 1983, Grey-Wilson 1997, Jäger & al. 2008). In addition to those treated in detail below, two more species are often cultivated in Belgium and might be found as casual escapes on dumps: Impatiens balsamina L. (now probably much rarer in cultivation than it used to be in the past) and I. walleriana Hook. f. (incl. I. sultani Hook. f.). The latter still is a very frequent garden plant. Finally, two more species were recently discovered in neighbouring countries and should be looked for: Impatiens edgeworthii Hook. f. is increasingly recorded as an escape in parts of Germany (Baade & Gutte 2008, John 2008, Weiss 2013, Kalveram 2014, Weiss 2020) and I. scabrida DC. (or perhaps rather I. tricornis Lindl., see Akiyama & Ohba 2016) persists since several years in Amsterdam in the Netherlands (see http://waarneming.nl/waarneming/view/51036938). Both are closely related and belong to the same clade but the former is glabrous and the latter densely hairy. They somehow resemble native Impatiens noli-tangere and might pass unrecorded.
Several species of Impatiens are reputed invasive environmental weeds. Two are on the black- or watchlist in Belgium as well (Impatiens glandulifera and I. parviflora). Most of these were initially introduced as ornamentals. More species, especially from mountainous regions in temperate Asia, are to be expected (Adamowski 2008).
1. Flowers pink, pinkish-purple (or rarely white). Leaves opposite, in whorls or alternate === 2
1. Flowers yellow or orange, often with brownish spots. Leaves alternate === 3
2. Leaves opposite or in whorls of 3(-5). Sepal spur 2-7 mm long, strongly bent === Impatiens glandulifera
2. Leaves alternate. Sepal spur 10-18 mm long, straight or slightly bent === I. balfourii
3. Flowers pale yellow, unspotted, 5-15 mm long. Sepal spur straight or slightly bent. Largest leaves with more than 20 teeth on either side === I. parviflora
3. Flowers yellow or orange, with brownish spots, 20-35 mm long. Sepal spur bent. Largest leaves with less than 20 teeth on either side === 4
4. Flowers yellow with small brownish spots. Sepal spur bent for ca. 90° (native) === I. noli-tangere
4. Flowers orange with large brownish spots. Sepal spur bent for ca. 180° (lying more or less parallel to the sac) === I. capensis
References
Adamowski W. (2008) Balsams on the offensive: the role of planting in the invasion of Impatiens species. In: Tokarska-Guzik & al. (eds.), Plant Invasions: Human perception, ecological impacts and management. Backhuys Publishers, Leiden, the Netherlands: 57-70.
Akiyama S. & Ohba H. (2016) Studies of Impatiens (Balsaminaceae) of Nepal. 3. Impatiens scabrida and allied species. Bull. Natl. Mus. Nat. Sc., ser. B 42(4): 121-130. [available online at: http://www.kahaku.go.jp/research/publication/botany/download/42_4/BNMNS_...
Baade H. & Gutte P. (2008) Impatiens edgeworthii Hook.f. – ein für Deutschland neues Springkraut. In: Evers C. (ed.), Dynamik der synanthropen Vegetation. Braunschweiger Geobotanische Arbeiten 9: 55-64. [available online at:
http://www.botanik-bochum.de/publ/OVBBV6_6_Kalveram_Impatiens_edgeworthi...
Bhaskar V. (2012) Impatiens L. (Balsaminaceae) of Western Ghats, South India: 283 p.
Chen Y.L., Akiyama S. & Ohba H. (2008) Balsaminaceae. In: Wu Z.Y. & Raven P.H. (eds.), Flora of China, vol. 12. Beijing: Science Press/ St. Louis: Missouri Botanical Garden Press: 43-113.
Dericks G. (2006) Ökophysiologie und standörtliche Einbindung neophytenreicher Gattungen (Impatiens, Solanum) der Rheintalaue. Inaugural-Dissertation, Institut für ökologische Pflanzenphysiologie und Geobotanik der Heinrich-Heine Universität Düsseldorf : 238 p. [available online at: http://docserv.uni-duesseldorf.de/servlets/DerivateServlet/Derivate-4379...
Grey-Wilson C. (1980) Impatiens of Africa. A.A. Balkema, Rotterdam: VIII + 235 p.
Grey-Wilson C. (1983) A survey of the genus Impatiens in cultivation. The Plantsman 5(2): 86-102.
Grey-Wilson C. (1997) Impatiens. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 5. Cambridge University Press, Cambridge: 159-163.
Jäger E.J., Ebel F., Hanelt P. & Müller G. (eds.) (2008) Rothmaler Band 5. Exkursionsflora von Deutschland. Krautige Zier- und Nutzpflanzen. Springer Verlag, Berlin: 880 p.
Janssens S., Geuten K., Yuan Y.M., Song Y., Kupfer P. & Smets E. (2006) Phylogenetics of Impatiens and Hydrocera (Balsaminaceae) using chloroplast atpB-rbcL spacer sequences. Syst. Bot. 31(1): 171-180.
Kalveram Th. (2014) Das Bunte Springkraut (Impatiens edgeworthii) in Essen-Borbeck (Nordrhein-Westfalen). Veröff. Bochumer Bot. Ver. 6(6): 47-49. [available online at: http://www.botanik-bochum.de/html/publ/OVBBV6_6_Kalveram_Impatiens_edgeworthii.pdf]
Lambinon J., Delvosalle L., Duvigneaud J. (avec coll. Geerinck D., Lebeau J., Schumacker R. & Vannerom H. (2004) Nouvelle Flore de la Belgique, du Grand-Duché de Luxembourg, du Nord de la France et des Régions voisines (Ptéridophytes et Spermatophytes). Cinquième édition. Jardin botanique national de Belgique, Meise: CXXX + 1167 p.
Matthews J., Beringen R., Boer E., Duistermaat H., Odé B., van Valkenburg J.L.C.H., van der Velde G. & Leuven R.S.E.W. (2015) Risks and management of non-native Impatiens species in the Netherlands. Reports Environmental Science 491. Available online at: https://www.researchgate.net/publication/283500931_Risks_and_management_...
Moore D.M. (1968) Impatiens. In: Tutin T.G. & al. (eds.), Flora Europaea, vol. 2. Cambridge University Press, Cambridge: 240-241.
Morgan R.J. (2007) Impatiens: The Vibrant World of Busy Lizzies, Balsams, and Touch-Me-Nots. Timber Press: 219 p.
Skálová H., Havlíčková V. Pyšek P. (2012) Seedling traits, plasticity and local differentiation as strategies of invasive species of Impatiens in central Europe. Ann. Bot. 110: 1429-1438. [available online at: http://aob.oxfordjournals.org/content/early/2012/01/12/aob.mcr316.full.pdf+html]
Slavík B. (1996) Rod Impatiens v České republice. Preslia 67: 193-211.
Weiss V. (2013) Zur Ökologie von Impatiens edgeworthii HOOK. f. in Mitteldeutschland. Mitt. florist. Kart. Sachsen-Anhalt 18: 15-29. [available online at: http://www.bv-st.de/Publ2013.htm]
Weiss V. (2015) Die rote Pest aus grüner Sicht: Springkräuter – von Imkern geschätzt, von Naturschützern bekämpft. Leopold-Stocker-Verlag, Graz.
Weiss V. (2020) Impatiens edgeworthii, an invasive balsam in Central Europe by its ecology. Does it be an aggregate species? [available online at: https://www.researchgate.net/publication/341055958_Impatiens_edgeworthii...
Yu Shengxiang (2012) Balsaminaceae of China: 214 p.
Yuan Y.M., Song Y., Geuten K., Rahelivololona E., Wohlhauser S., Fischer E. & Smets E. (2004) Phylogeny and biogeography of Balsaminaceae inferred from ITS sequences. Taxon 53(2): 391-403.