Impatiens noli‐tangere L.

Abstract

Balsaminaceae. A glabrous annual herb, 20–180 cm tall. Stems translucent yellow/green often suffused with red, simple or branched, becoming swollen at nodes; branches of the third order present on well-developed plants. Stems to 2 cm diameter, becoming hollow with age. Roots simple, to a depth of 10–15 cm. Leaves 1.5–10 × 1.5 cm, with 5–8 pairs of lateral veins, opposite becoming alternate, ovate–elliptical to ovate–lanceolate or oblong, base cuneate to subcordate, apex obtuse to acute, mucronate, margin serrate to subcordate, often glandular near base. Teeth 7–16 (−20) on each side of leaf, usually mucronate, 2–3 mm deep. Flowers (2–) 3–6 in axillary racemes, some cleistogamous, the others (1.5–) 2–3.5 cm, yellow with small brownish/red spots. Flower resupinate, being twisted through 180°, with 3 sepals and 5 petals. The lower sepal is large (8–) 10–20 × 7–13 mm, almost funnel-shaped, longer than wide, gradually contracted to a nectar-tipped spur. This spur is 6–12 mm, curved, rarely bent through 90° or more. The two outer opposite sepals are flat and oblique, green. Upper petal separate, small, broad and hollow with pale glaucous-green vein on back. Remaining 4 petals united into 2 lateral pairs, oblique and irregularly lobed (see illustrations in Ross-Craig (1952) and dimensions in Fig. 10). The dorsal petal forms a characteristic hood over the androecium and the united lateral petals provide a prominent lip for alighting insects. Stamens 5, fused together closely around the ovary, alternate with petals, filaments usually short and inverted–subulate, distant. Anthers short and thick, united around the stigma. Gynoecium of 5 united carpels, 2 to many ovules in each locule, inserted in the inner angles. After flowering, the whole corolla falls from the plant. Capsule 5-chambered, c. 1.5 cm, linear, glabrous, containing 1–9 seeds with mass c. 2–6 mg. Seeds obovoid–obpyriform, 4-angled in transverse section, 3.3–4.6 mm long, 1.4–2.2 mm wide, 0.8–1.5 mm thick; longitudinal ridges, one at each angle, acute to obtuse 0.06–0.2 mm wide, 0.06–0.3 mm high (Anderberg 1994). Floral structure of Impatiens noli-tangere. Seventy-five newly mature flowers from an experimental population of over 1000 plants at the University of Reading, Reading, UK, were measured in July 2001. Floral measurements follow Schemske (1978), apart from N, the distance from the pollen source to the nectar source, determined by dissection. Impatiens noli-tangere has a variable phenotype, with plants ranging from < 15 cm tall, unbranched and producing 1–10 cleistogamous flowers to > 150 cm tall, with considerable primary and some secondary branching and > 100 chasmogamous flowers (‘broom’ type of Falińska 1979). Shade, moisture and nutrient levels may affect the appearance of the phenotypes. The size of the cotyledons is important for the later development of the plant (Falencka 1983). A molecular survey of the genetic affinities of samples in 1999 from the Lake District and North Wales and a reference population from Switzerland was performed using AFLP and ISSR analyses. There was clear differentiation between the populations of I. noli-tangere in Wales and those in the Lake District, and between both UK populations and the Swiss population (P.E.H. et al.). Most of the genetic variation was partitioned between rather than within regions and there was little evidence of gene flow between regions. There was little differentiation between metapopulations in the Lake District and a modest estimate of gene flow (Nm = 0.61) compared with greater evidence of population differentiation in Wales and a very low estimate of gene flow (Nm = 0.13). No varieties have been recorded from the UK, but several have been reported elsewhere. These include var. albiflora Schwarz and var. micrantha Rouy & Fouc. in central Europe (Browicz & Zieliński 1976), var. pallescens Nakai from Korea and the Far East (Hong & Oh 1993) and var. parviflora Kitagawa from Japan (Kitagawa 1954). Impatiens is essentially a montane genus of the Old World, containing over 900 spp. (Cullen et al. 1997), half of which occur in the subcontinent of India. Impatiens noli-tangere is the only native Impatiens species in the UK: the introduced I. glandulifera, I. parviflora and I. capensis are also established. Impatiens noli-tangere (touch-me-not balsam) is a scarce native annual of wet woodlands, streams and lakesides, which is locally common in mid-Wales and the English Lake District. Classified by Preston & Hill (1997) as a Eurasian temperate species, Impatiens noli-tangere is generally considered to be native only in the English Lake District and mid-Wales (Watson 1883) where it has been recorded from 24 10-km squares since 1950 (Fig. 1). Preston et al. (2002) record I. noli-tangere as native from 16 10-km squares since 1987, 4 from 1970 to 1986 and 1 pre 1970. The two outlier records of native plants in Fig. 1 (south of the Lake District and mid-way between mid-Wales and the Lake District) are considered alien plants by Preston et al. (2002). Coombe (1956b) suggested that the presence of the monophagous Eustroma reticulatum (Lepidoptera) on the plants in the Lake District and mid-Wales (see Section IX (A) ii) can be used to distinguish sites where it is native from sites in southern England where it is an escape. Preston (1986), however, suggests caution here. The distribution of Impatiens noli-tangere in the British Isles. Each symbol represents at least one record in a 10-km square of the National Grid. Native: (○) pre 1950, (•) 1950 onward; introduced: (×) pre 1950, (+) 1950 onward. Mapped by H. R. Arnold, Biological Records Centre, Centre for Ecology and Hydrology, Monks Wood, mainly from records collected by members of the Botanical Society of the British Isles. In 1990, an estimated 7650 plants were recorded from 26 sites in the English Lake District (Hatcher & Alexander 1994). In a re-survey in 2000, an estimated 25 655 plants were found from 55 sites (Fig. 2) (Hatcher 2001a). Twenty-nine of these populations, comprising 20 245 plants, were from sites first found after 1990: in 2000 there was a 16% decrease in the number of plants found at sites extant in 1990 (Hatcher 2001a). In the Lake District, the plant is concentrated in nine areas: the east and west shores of Windermere; the east shore of Coniston Water; the east and west shores of Derwentwater; the Ambleside–Rydal area; the Broughton-in-Furness area; Dunnerdale; and Muncaster (Fig. 2). In 1991, 3295 plants were also recorded from 17 sites in Wales (Hatcher & Alexander 1994): to the west and north of Dolgellau; the east of Montgomery; the south-east of Welshpool. The distribution of Impatiens noli-tangere in the English Lake District in 2000. 10-km National Grid squares superimposed. Numbers of plants per 1-km square recorded: [1] > 1000 plants; [2] 101–1000 plants; [3] 11–100 plants; [4] < 11 plants; [5], plants present in 1990 but not in 2000. Data from Hatcher & Alexander (1994) and Hatcher (2001a). Impatiens noli-tangere has been recorded as an alien from 81 10-km squares since 1950 and 18 pre 1950 (Fig. 1); Preston et al. (2002) record it as an alien in 35 10-km squares post 1987, 6 between 1970 and 1986 and 63 pre 1970. In some of these cases the plant has been established for a number of years; for example, for at least 40 years (1933–74) near a pond in Surrey (Lousley 1976), and it has been suggested that the plant should be considered as a native in sites in Northumberland (Swan 1993) and West Yorkshire (Lees 1888). Impatiens noli-tangere has been cultivated occasionally (Grieve 1931; Grey-Wilson 1983; Cullen et al. 1997) and throughout England there have been scattered records of it as a naturalized garden escape (e.g. Murray 1896; de Tabley 1899; Druce 1930; Cadbury et al. 1971; Messenger 1971; Roe 1981). However, the distribution and status of the plant in the UK outside of the Lake District and mid-Wales (Fig. 1) are uncertain as many old records were misidentifications for one of the introduced yellow–orange flowered balsams, either I. capensis or I. parviflora (de Tabley 1899; Salmon 1931; Coombe 1956a). For example, the only Wiltshire record for I. noli-tangere was in error for I. capensis (Fl. Wilt.), and the only herbarium specimen of I. noli-tangere for Lincolnshire proved to be I. parviflora (Gibbons 1975). Outside the UK, I. noli-tangere is found from the Iberian peninsula (where it is rare) and southern France across Europe (although absent from the extreme south), Russia and Siberia to Japan and Kamchatka, and also in North America from South Alaska to Washington State, Manitoba, Saskatchewan and British Columbia (Fig. 3). It is found up to 67°30′ N in Sweden. The world distribution of Impatiens noli-tangere. (Redrawn from Hultén 1971). The native presence of I. noli-tangere in North America remains controversial (Ornduff 1967; Jouret 1977). It was first described in North America in 1803, but Rydberg (1910) believed that this was a misidentification of I. pallida. Impatiens noli-tangere was re-identified from north-western Washington State in 1890 (Rydberg 1910; Ornduff 1967) but Rydberg (1910) considered it a separate, new, species, I. occidentalis Rydberg, and it is listed as such by Abrams (1951). Impatiens noli-tangere is considered a circumpolar ring species, as is I. capensis (Hultén 1971; Jouret 1977). Impatiens noli-tangere reaches altitudes of 1400–1500 m in central Europe, 1500 m in France and 700 m in Norway (Hultén 1971), and to about 2000 m in the Chinese mountains (Alt. N.W. Eur.). In Wales and the English Lake District it is found up to 210 m, although in the latter area 89% of the plants occurred below 100 m (Fig. 4). Altitudinal distribution of Impatiens noli-tangere in the English Lake District in 2000. Total number of plants: 25 655. Data from Hatcher (2001a). Impatiens noli-tangere is a therophyte, occurring on damp to wet, occasionally waterlogged soils mainly in damp woods, on the edges of rivers, streams and lakes (wetness value 7, Ellenberg 1988). In the English Lake District, 78% of the I. noli-tangere plants recorded in the 2000 survey occurred in areas with an annual rainfall of 1600–2000 mm, 17% in areas with 1200–1600 mm and 5% with 2000–2400 mm annual rainfall (Hatcher 2001a; average annual rainfall figures from Halliday 1997). Impatiens noli-tangere is considered nitrophilous (nitrogen value 6, Ellenberg 1988); in riverside woods it is frequently fertilized by mud after flooding. It occurs mainly in partial shade, generally with more than 5% relative light (light value 4, Ellenberg 1988) and in fairly warm conditions (temperature value 5, Ellenberg 1988). Its distribution suggests that all these factors, and particularly rainfall, are important, but it is notably absent from some suitable areas in the UK. Impatiens noli-tangere is part of the early succession herb flora of forests, and as such is maintained in some mature stands only by soil disturbance from, for example, trampling by animals, forestry operations, vehicle tracks, local drainage and wind-throw of trees (Faliński 1986; Jankowska-Błaszczuk & Grubb 1997). In the Russian far-east it is part of the post-fire succession (Komarova 1996). Impatiens noli-tangere grows on a range of open-textured soils, from those which are constantly damp to those, for example on the edge of lakes, which are periodically waterlogged. It generally grows on mull-type soils with high base status, rich in humus and available nitrogen, and can also occur on gley soils in alder carr. It occurs in weakly acidic to circumneutral soils but is never found on very acid soils (Ellenberg 1988). Details of a soil analysis of five typical sites in the English Lake District containing the plant are given in Table 1. Dzwonko (2001) found I. noli-tangere growing in soil with pH 4.81 and 4.62, total nitrogen 0.186% and 0.177% and cation exchange capacity 6.54 and 5.24 meq g−1 soil, in ancient and recent woodland in Poland, respectively. Likewise, Laskowski et al. (1995) recorded I. noli-tangere from weakly leached gleys in a Polish oak–hornbeam forest with pH 4.9. Of the plants recorded in the 2000 English Lake District survey (Hatcher 2001a), 92% grew in areas underlain by rocks of the Silurian Windermere Supergroup (mainly Coniston Grits and Bannisdale Slates), 7% by the Ordovician Borrowdale Volcanic Group and 1% were underlain by the Ordovician Skiddaw Slates. Of the plants recorded from the 1991 survey of Wales and the borders (Hatcher & Alexander 1994), 75% of I. noli-tangere grew in areas underlain by Upper Cambrian rocks, 18% by Silurian rocks of the Wenlock Formation and 7% by rocks of the Ordovician Hagley Shale Formation. In the UK, and particularly the Lake District, Impatiens noli-tangere occurs mainly in open deciduous woodland, although it is also found in grassland, gardens and parkland (Table 2). The woods in which it occurs have a high canopy, sparse understorey and low herb layer. In drier soils in the Lake District, I. noli-tangere occurs mainly in Quercus petraea woodland, often with Fagus sylvatica and formerly sometimes with Ulmus glabra. Introduced tree species include Acer pseudoplatanus, Aesculus hippocastanum, Larix spp., Picea abies and Abies spp. In several Lake District sites large colonies of I. noli-tangere occur under single large A. pseudoplatanus, where little other ground cover is present. The understorey in these woods is predominantly Corylus avellana coppice with frequent Fraxinus excelsior and occasional Crataegus monogyna, Ilex aquifolium, Betula spp., A. pseudoplatanus seedlings and Sambucus nigra. Some of these woodlands correspond to Peterken's (1981) stand type 1D, ‘western valley ash–wych elm woods’ in which I. noli-tangere is mentioned as a rare species, and to NVC W9 (Fraxinus excelsior–Sorbus aucuparia–Mercurialis perennis woodlands) and W10 (Quercus robur–Pteridium aquilinum–Rubus fruticosus woodland, Rodwell 1991) although I. noli-tangere is not mentioned in the NVC (Rodwell 1991). In conifer plantations, I. noli-tangere is predominantly restricted to gaps in the canopy caused by streams or wind-throw. In wetter habitats, I. noli-tangere occurs predominantly in alder woodland (W7: Alnus glutinosa–Fraxinus excelsior–Lysimachia nemorum woodland, Rodwell 1991) with occasional Fraxinus excelsior. The understorey is again Corylus avellana coppice, F. excelsior, Betula spp., and A. glutinosa seedlings, and less commonly occasional Crataegus monogyna, and Ilex aquifolium on the drier edges. Impatiens noli-tangere has few associated species in the herb layer and often forms pure stands. A list of co-occurring species in 37 woodland sites in the English Lake District is given in Table 3. Impatiens noli-tangere has occurred with I. parviflora in several places on the wooded slopes above the western shore of Windermere since at least the 1950s (Coombe 1956a). However, Coombe (1956a) suggested that I. noli-tangere reached its maximum development in areas too wet for I. parviflora. Impatiens noli-tangere has also been recorded associated with I. glandulifera in Sweden (Larsson & Martinsson 1998) but is not associated with this species in the UK. Outside the Lake District and North Wales, I. noli-tangere has been recorded from damp woodland in the New Forest, Hampshire, where it grew in profusion with Athyrium filix-femina, Dryopteris affinis, D. carthusiana and Hydrocotyle vulgaris (Gimingham 1957). In central Europe, I. noli-tangere is considered part of the Carex remota group of woodland herbs occurring in damp to fairly wet less acid soils and is associated also with Equisetum sylvaticum, Galium aparine, Lamium maculatum, Silene dioica, Stellaria nemorum, Urtica dioica and Veronica montana (Ellenberg 1988). Here I. noli-tangere occurs in a wide variety of woodlands from quite dry Allium ursinum-rich beech woods through to swampy alder forests. Impatiens noli-tangere occurs mainly in ancient woodlands but also in recently wooded abandoned pasture, arable land and old gardens (Koerner et al. 1997; Falińska 1999; Dzwonko 2001). Four main woodland associations in which it is abundant may be distinguished. The characteristic damp mixed beech woods of this association (Fraxino-Fagetum or Querco-Carpinetum elymetosum/asperuletosum) with a dominant I. noli-tangere herb layer have been termed ‘touch-me-not mixed beech woods’ (Ellenberg 1988) to distinguish them from Melica–beech woods and fern–beech woods. Likewise, Miadok (1971) denoted a Piceto-Fagetum carpaticum cilicicolum variant with I. noli-tangere. In these woods, I. noli-tangere occurs with the moisture indicators listed above and also Circaea lutetiana, Stachys sylvatica and Festuca gigantica (Ellenberg 1988; Tichý 1997). In the Ukranian Carpathians, I. noli-tangere occurred in this type of wood in clear fellings in areas managed for shelter woods (Gorshenin et al. 1972; Tichý 1997) noted I. noli-tangere in the geobiocenosis type Hordelymus europaeus-Asperula odorata filicies-Oxalis acetosella within this woodland association. Impatiens noli-tangere occurs in sycamore, Acer pseudoplatanus, forests with Corydalis spp. (Corydali-Aceratum) in shaded and cool sites exposed to the north, or in gorges or scree slopes, rich in fine earths and nutrients. Acer pseudoplatanus and Fraxinus excelsior are the main tree species, with Ulmus scabra, Tilia platyphyllos, Acer platanoides, Fagus sylvatica and Abies alba also common (Moor 1973; Ellenberg 1988). Impatiens noli-tangere occurs in the Tilio-Carpinetum (T.-C.) association. These forests occur mostly outside the range of beech, chiefly with Quercus robur and Q. petraea, Tilia cordata, Acer pseudoplatanus and in the north-east with Picea abies (Ellenberg 1988). T.-C. corydaletosum cavae occurs in sites including Białowieża Primeval Forest, Poland (Pigott 1975; Falencka 1981, 1983; Faliński 1986) where it is abundant along with Lysimachia vulgaris, Stellaria nemorum, Equisetum sylvaticum, Brachypodium sylvaticum and less commonly with Ranunculus repens, Urtica dioica, Athyrium filix-femina and Geum urbanum (Faliński 1986). Here, I. noli-tangere can be one of the most abundant herb species in the soil seed bank (Jankowska-Błaszczuk 1998). In cooler and more oceanic climates, I. noli-tangere occurs in stitchwort–oak–hornbeam woods (T.-C. stachyetosum sylvaticae or Stellario-Carpinetum-stachyetosum). In this association in the Białowieża Primeval Forest, I. noli-tangere is dominant along with Anemone nemorosa, Oxalis acetosella, Lamiastrum galeobdolon, Cardamine bulbifera, Galium odoratum, Aegopodium podagraria, Isopyrum thalictroides, Stachys sylvatica, Corydalis solida and Gagea lutea (Faliński 1986). In all these woods, I. noli-tangere is considered a moisture indicator along with Athyrium filix-femina, Urtica dioica, Circaea lutetiana and S. sylvatica (Ellenberg 1988). Impatiens noli-tangere also occurs on forest roads in these woodlands (Plantagineta), characterized by Plantago major, Poa annua, Prunella vulgaris, Festuca gigantea, Urtica dioica, Stellaria nemorum and Rumex sanguineus (Faliński 1986). Species associations for I. noli-tangere in an oak–ash woodland in western Norway, including Alno-Prunetum, Alno-Ulmion and Ulmo-Tilietum communities are given by Austad & Skogen (1990). Impatiens noli-tangere occurs in many flood-plain wood associations including poplar–willow (Salici-Populetum) associations dominated by Populus nigra, Carex spp. or Geum urbanum. These associations grade through to poplar-dominated flood-plain woods (Sambuco-Populetum) including those generally dominated by Ulmus minor or planted Fraxinus excelsior. Impatiens noli-tangere occurs in elm flood-plain woodlands (Omphalodo-Ulmetum) rich in Fagus spp. and with Salix alba (Ellenberg 1988). Impatiens noli-tangere is one of the dominant herbs in black (common) alder, Alnus glutinosa, woods throughout Europe (Passarge 1956; Ellenberg 1988; Döring-Mederake 1990; Prieditis 1997; Vasilevich & Stchukina 2001). These woods can be divided into alder swamp woods (Carici elongatae-Alnetum), alder flood-plain forests (Circaeo-Alnetum) and alder–ash woods (Pruno-Fraxinetum, Quercus robur and ash associations on muddy peat). These assemblages are a diagnostic group for broad-leaved forests including Querco-Fagetea, Fagetalia and Alno-Ulmion. Prieditis (1997) provides many examples of species associations for I. noli-tangere in these communities. Passarge (1956) noted that a mixture of fen species and species associated with base-rich clay soils at least periodically wet (e.g. Circaealutetiana, Geum urbanum, Glechoma hederacea, Ranunculus ficaria, Rumex sanguineus) were associated with I. noli-tangere in these habitats, while in the flood-plain alder forests, Fali¢ski (1986) noted greatest cover by Lamiastrum galeobdolon, Chrysosplenium alternifolium and Geum rivale, along with I. noli-tangere. Pretzell & Reif (1999) recognize a characteristic I. noli-tangere formation in the Carici elongatae-Alnetum of the upper Rhine valley; this also contains Poa palustris and Ranunculus repens as characteristic species. Deforestation of the Circaeo-Alnetum flood-plain in the Białowieża Primeval Forest 200 years ago led to the development of rich meadow communities (Cirsietum-rivularis, Falińska 1999). Impatiens noli-tangere reappeared 20 years after these meadows were abandoned, as the community was reverting to Betula pendula, Salix spp. and A. glutinosa scrub. In the Russian Far East, I. noli-tangere is one of the initial colonizing species of broadleaved/Pinus koraiensis forests in post-fire successions (Komarova 1996) along with Conyza canadensis, Epilobium davuricum, Chelidonium asiaticum, Lamium barbatum, Chamerion angustifolium, Urtica angustifolia, Artemisia rubripes and Carex campylorhina. Impatiens noli-tangere is grazed by deer and cattle, and trampling of stands occurs frequently (Markov 1991). In the English Lake District grazing cattle remove all leaves and side branches, leaving the bare main stem. Impatiens noli-tangere responds poorly to competition, although it was reported to have a deleterious effect on first-year Abies alba seedlings in Romanian mixed fir and beech forests (Pauca-Comanescu et al. 1974). In Białowieża Primeval Forest, Poland, greater survival (80% vs. 62–67%), and larger plants were recorded in weeded plots than in unweeded, respectively, with considerable evidence of competition with the herb layer (Falencka 1981, 1983). In the English Lake District, plants recorded in 1990 were under threat of encroachment by Pteridium aquilinum (37% of colonies), Rubus spp. (21%), Urtica dioica (18%), Rhododendron ponticum (11%) and other ground vegetation (10%) (Hatcher & Alexander 1994). The interaction with light and moisture appears crucial here. Although the plant responds well to an opening up of the canopy (for example by selective tree or branch removal), if the soil is too dry then I. noli-tangere is soon out-competed by the aforementioned species and coppice regrowth, surviving only in the wetter habitats. Management of a neglected fodder woodland in western Norway, which involved removing the understorey tree layer of Alnus incana, re-pollarding Ulmus glabra and Corylus avellana and mowing the field layer once or twice a year, led to an increase in I. noli-tangere (Austad & Skogen 1990). Impatiens noli-tangere was frequent, but at low abundance, in the wood before the management; however, in the first and second years after management it became completely dominant over large parts of the forest for several weeks. In some years two generations of plants were produced: one in spring and the other later after an early mowing. However, 5 years after management I. noli-tangere populations stabilized at moderate levels (Austad & Skogen 1990). Impatiens noli-tangere often forms dense single-species stands, resulting from synchronous germination of seeds in the spring. Seedlings appearing at the beginning of the germination period have a greater chance of survival, whereas seedlings reaching the soil surface at the end of the 3-week germination period (first 10 days of June in Poland) usually die after a few days (Falencka 1983). Individual I. noli-tangere populations in the English Lake District usually contain 1–6000 plants (Hatcher 2001a), with up to 25 000 plants having been recorded in one site between 1990 and 2000 (Fig. 5); populations fluctuate markedly from year to year (Fig. 6). Similar temporal variability has been noted in the Białowieża Primeval Forest, Poland: 377–1625 I. noli-tangere were recorded annually in one 10-m2 plot and 590–2055 individuals in another plot over 7 years’ observations (Faliński 1986). Distribution of Impatiens noli-tangere colony sizes in the English Lake District 1990–2000. All records between 1990 and 2000 combined. Data from Hatcher (2001a). Size of Impatiens noli-tangere populations at Coniston Water (open bars) and Derwentwater (filled bars) 1990–2002, Lake District, England. Derwentwater sites were not sampled in 1993. The Coniston Water total for 2001 is estimated as not all sites could be visited owing to food-and-mouth disease restrictions. Data from Hatcher & Hooson (2000), Hatcher (2001a,b, 2002). Between 1993 and 2000, I. noli-tangere became extinct in 23 sites in the English Lake District (Hatcher 2001a). These sites had significantly fewer plants the year before disappearance than populations that remained (populations lost: 32 ± 9 plants, populations remaining: 358 ± 58 plants, t = 5.59, P < 0.001). Apart from this, there was little correlation between population size and degree of change the following year (r = 0.066, P > 0.05, n = 152). Plants rarely re-appeared at sites from which they were lost: there were only 10 records of re-appearances in the English Lake District between 1990 and 2000, only a couple of which could have been genuine re-colonizations (Hatcher 2001a). Large-scale extinctions have been reported: Tichý (1997) noted the complete disappearance of the plant over a 30-year period from a Czech forest where it was formerly abundant. In the UK, I. noli-tangere rarely occurs at densities above 100 plants m−2 (P.E.H.), although densities of up to 995 seedlings m−2 have been recorded in continental Europe (Schmucker & Drude 1934). In continental European alder woodland, densities ranged from 29 seedlings m−2 (27.9 g m−2 fresh, 0.997 g m−2 dry) (Eliáš 1987) through 64 ± 21.5 (Falińska 1979) to 125–167 seedlings m−2 (Falencka 1981). In continental European oak–hornbeam forests densities between 3 and 130 plants m−2 have been recorded (Falińska 1979; Falencka 1981; Eliáš 1987). In the Białowieża Primeval Forest, plant density seldom exceeded 10–50 m−2 within woodland, but in sites with more light and along forest paths the density varied between 100 and 200 plants m−2 (Faliński 1986). Several studies have investigated the growth of Impatiens noli-tangere in contrasting habitats. Markov (1991) considered that I. noli-tangere grew more vigorously in a dry as opposed to a wet site in the same forest, and that the plants were more variable and allocated more to root production in the wet location. However, others demonstrate that the plant is more successful in the wetter alder woods as opposed to the drier ash (Eliáš 1987) or oak–hornbeam forests (Falencka 1981, 1983). Alder wood populations of I. noli-tangere had a greater density and degree of space filling (Falencka 1981) than those in oak–hornbeam forests. Furthermore, individual plants were 3- to 5-fold heavier in alder woods and were more variable (Falencka 1983; Eliáš 1987). However, Falińska (1979) and Eliáš (1987) found that the oak–hornbeam and ash wood I. noli-tangere populations, respectively, were denser and formed by smaller and lighter plants than those in alder wood populations. The alder woods were considered to have higher soil fertility, better light conditions and higher water levels than the ash or hornbeam woods (Falencka 1981, 1983; Eliáš 1987). Plants growing on and near forest roads in the Białowieża Primeval Forest were taller, heavier, at a greater density and produced twice as much seed than plants growing in alder flood-plain or oak–hornbeam forest populations (Falińska 1979). Cleistogamous flowers were much rarer in roadside populations and here plants often formed a ‘broom’ type with the top of the shoot covered with leaves and numerous branchings, seldom noted elsewhere (Falińska 1979). Site conditions affect both the proportion of plants flowering and the proportion of cleistogamous flowers. In the Białowieża Primeval Forest, 60% of plants flowered in woodland with 70–90% tree cover, 75% with 70% tree cover and 90% in less than 50% tree cover (Falińska 1979). In the woodland, 90–96% of flowers were cleistogamous, but in plants transplanted to a garden with high light levels, only 18–26% of flowers were cleistogamous (Falińska 1979). Impatiens noli-tangere stands are associated with soil disturbance. Markov (1991) considered that I. noli-tangere grows only where there are at least minor disturbances of the forest floor, including human activity and temporary water flows. Jankowska-Błaszczuk & Grubb (1997) categorized I. noli-tangere as a species which did not need large-scale disturbances of the tree canopy for establishment, but suggested that disturbance by wild boar (Sus scrofa) and bison (Bison bonasus) coupled with reduction in root competition from trees and herbs by disturbance of the soil was very important for its establishment in the Białowieża Primeval Forest. However, Jankowska-Błaszczuk (1998) found an 8-fold reduction in seed density in areas of oak–hornbeam forest with soil disturbed by wild boar than in undisturbed areas, although seedlings still appeared frequently in the disturbed areas. It also occurs after clear fellings and in areas managed for shelter wood in the Ukrainian Carp