Impatiens glandulifera is an erect, annual herb which stands from 1-5 m tall. Its leaves are glabrous, simple, oblong, ovate to elliptical, and arranged oppositely. Leaves are 5-18 cm inches long, 2.5-7 cm wide, and sharply serrated. Stems are reddish coloured, multi-branched, erect, hollow, and hairless with large swollen nodes. Roots to a depth of 10-15 cm. Its inflorescences are racemes of 2-14 flowers 2.5-4 cm long, which range in colour from white, pink, red, and purple. Flowers are irregular, bearing 5 petals and zygomorphic, with the lowest sepal forming a sac that ends in a straight spur. Seed capsules are 1.5-3.5 cm long, up to 3.5 cm wide, and contain 4-16 seeds (ANHP, 2004; Helmisaari, 2006; Beerling & Perrins, 1993; Willis & Hulme 2004).
Impatiens glandulifera has been found to be an important source of nectar for bumble-bees and to their conservation, especially in the changing seasons and among agricultural lands (Stary & Tkalcu, 1998).
An annual species, Impatiens glandulifera germinates in February to March. A period of chilling at 4º C for over 45 days is necessary to break seed dormacy. Germination is epigeal and occurs relatively early giving seedlings an advantage over other plants as long as they are not exposed to frost. After 12 days the first lateral roots emerge and by 18 days these roots, the radicle, and hypocotyl greatly elongate. Within four weeks the testa is lost and the cotyledons become photosynthetically active. The first true foliage emerges as a whorl of 4 leaves, with subsequent whorls of 3. Seed sets occur about 13 weeks after flowering (Beerling & Perrins, 1993; NWCB, 2007)
Impatiens glandulifera is a popular ornamental internationally. Many of its introductions to new locations have resulted from its unintentional establishment after \"escaping\" confined habitats (Beerling & Perrins, 1993).
Impatiens glandulifera requires moist and relatively nutrient rich habitats and does particularly well in frequently disturbed areas. Tolerant of a wide range of soil textures and structures I. glandulifera occurs in fine and course alluvium, maritime shingle, free-draining mineral soils, peats, and colliery spoil. It most commonly occurs in riparian zones, but may also be found in open areas of forests, forest edges, riverine and fen scrub, roadsides, and man-made structures. I. glandulifera is tolerant to a pH range of about 4.5-7.7, elevations 1800-3200 m, and relatively low sunlight. I. glandulifera was found to require a growing season of 2195 day-degrees in Europe. Distributions may also be constrained by its high moisture requirement and frost sensitivity. Late spring and early autumn frosts are known to kill seedlings and adults respectively outside its native range (DAISIE, 2009; Beerling & Perrins, 1993; Beerling, 1993; Hedja & Psyek, 2006).
Impatiens glandulifera is a summer-annual, therophyte with no vegetative reproduction. Seed production varies with plant density. From germination flowering takes about 13 weeks and continues for another 12 weeks. Seed capsules mature producing up to 10 seeds and burst, expelling the seeds 3-5 m. Individual plants may produce more than 2,500 seeds in a vegetative period with taller plants producing more seeds and pods. I. glandulifera competes on river banks through synchronous germination of a large seed bank providing sufficient biomass to suppress neighbouring species. This synchronous reproductive strategy is thought to rely on habitats with seasonally predictable disturbances such as flooding (Beerling & Perrins, 1993; Burkhart & Nentwig, 2008; Sheppard et al, 2005; Willis & Hulme, 2004).
Many introductions of Impatiens glandulifera are the result of their use as decorative plants (Beerling & Perrins, 1993), and as a nectar source for commercial bees and planted by beekeepers (Helmisaari, 2006).Transportation of topsoil bearing overwintering seeds a common means of dispersal of Impatiens glandulifera (Beerling & Perrins, 1993).
Impatiens glandulifera is known to compete with and displace native plant species as in the case of European native Impatiens noli-tangere, reduce native plant diversity, and negatively impact habitat for wildlife. Its hardiness, high reproductive rate, rapid growth, early germination, and propensity to establish thick, dense stands all make I. glandulifera a very formidable competitor. Hulme & Bremner (2006) reported that the introduction of Himalayan balsam resulted in more than a 25% reductions in species richness and diversity. However, studies in some locations claim effects of I. glandulifera on native biodiverstiy are mild, and that it predominately displaces non-native weeds. I. glandulifera promotes erosion in watercourses and can alter water flow. Its modest root system and characteristic dying back in the fall renders river banks more susceptible to erosion in the fall and winter, which damages river banks and increases flooding. I. glandulifera can also compete with and exclude native plants from pollination. It produces nectar sugar at a significantly higher rate (0.47 ± 0.12 mg per flower per hour) than many of its native neighbours in introduced habitats. In central Europe, its main invasive range, no plant produces more than 0.3 mg per flower per hour. Being a more appealing source of nectar to pollinators including bumblebees, honeybees, moths, and wasps, I. glanulifera has been demonstrated to cause pollinators to neglect native plants, reducing instances of their pollination and their resultant reproductive success. Finally because of their high holocellulose content, I. glandulifera stems persist throughout the winter and suppress competing seedlings the following spring (ANHP, 2004; NNSS, undated; DAISIE, 2006; Burkhart & Nentwig, 2008; Chitka & Schurkens, 2001; Lopezaraiza-Mikel et al, 2007; Perrins et al, 1993; Hulme & Bremner, 2006).
is a highly invasive plant and should not be introduced to new locations. Care should be taken to prevent ornamental and contained plants from establishing in the wild. Studies indicate once widely established, eradication is extremely difficult. Maintenance of a dense grass sward along river banks may prevent the germination of I. glandulifera
seedlings (Centre for Ecology and Hydrology, 2004; Wadsworth et al
Please follow this link for more details on the management and control of Impatiens glandulifera.