Impatiens parviflora D.C., 1824
Common names: Small yellow balsam [En], Balsamine à petites fleurs [Fr], Klein springzaad [Nl], Kleines Springkraut [De]
Invasive species (Central Europe)
Meise, BRABANT ● Belgium
Description: Glabrous, erect annual herb, usually 20-60 cm tall, rarely reaching 150 cm. It is single stemmed or branched from the lower nodes, with third-order branches in well-developed plants. The leaves are simple, alternate, ovate, 5-12 cm long and 2.5-5 cm wide, sharply serrated at the edges with 20-35 teeth on each side. Petioles carry stalked glands which may serve as extrafloral nectaries. Flowers in axillary racemes of (1-) 4-10 (-15). Racemes as long as the upper leaves or longer. Flowers 10-15 mm long including their spur, upright (as opposed to hanging flowers in other Impatiens species). Flowers pale yellow with red spots on the inside. Petals 5, the anterior large and single, the others united in pairs. Capsule linear to club-shaped, 15-20 mm long, glabrous and green. Seeds 1-5 per capsule, oblong, 4-5 mm long with fine longitudinal striations. The root system is shallow, the primary root usually short-lived and replaced by laterals and adventitious roots from the lower node (Hegi, 1912; Coombe, 1956; Sebald et al., 1998).
Biology: Small yellow balsam is intolerant to late frost. Seeds may be dispersed over long distances via epizoochory (mammal fur) and water.
Habitat: I. parviflora is the only exotic plant being dispersed on a large scale in European forests. It prefers shaded and moist nutrient-rich stands but can also develop in acidic conditions. It thrives in beech and alder forests, but also in parks, hedgerows, forest edges, waste grounds and ruderal habitats. Its development is favoured by habitat perturbation and forest management practices (e.g. soil compaction). It easily penetrates into degraded and floristically impoverished communities, but dense groundlayer may provide an effective barrier to its expansion. Up to 800 m.
Distribution: Originated from Asia (Siberia, Turkestan), Impatiens parviflora is one of the most widespread aliens to Central Europe. Dense populations inhabit most of the sites available. Impatiens parviflora is sometimes even considered to have decreased in its occurrence in the last years and to be in “post-invasive stage”.
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.
Invasive Species in Belgium