Josef Holec, Markéta Kosánová and Josef Soukup
Department of Agreoecology and Plant production, Faculty of Agrobiology, Food and Natural Resources, Czech University of Life Sciences Prague, 165 00 Prague 6 – Suchdol, Czech Republic
Rosa multiflora Thunb. (Rosaceae) is a shrub native to East Asia (China, Korea and Japan), preferring soils with higher nutrient content. In Central Europe, this species is cultivated for its ornamental flowers and it is a parental species for many ornamental Rosa hybrids. The relatively small fruits are eaten by frugivorous birds (such as Turdus merula) and the species can easily escape from cultivation. It is a problematic environmental weed in North America (Banasiak & Meiners 2009). Větvička (1995) refers to R. multiflora as an important cultivated species giving no information about its feral occurrence. Currently, it is classified as a casual neophyte (Pyšek et al. 2012) that can be found not only in cities, but also in the open landscape (Tichá 2004).
In 2017, we commenced monitoring in a part of the Prague 6 district – Suchdol, Sedlec, Lysolaje in north-western borders of the city of Prague in a close proximity to the Vltava River. In total, 54 plants of R. multiflora were recorded. We found both cultivated (30%) and escaped (70%) individuals. This indicates that R. multiflora can easily become feral in this region and currently feral plants are already more common than cultivated ones. In the group of feral plants that escaped from cultivation, 87% were mature flowering plants and only 13% were juvenile individuals in a vegetative stage. A relatively low share of juvenile individuals can be interpreted as lower intensity of invasion since the plant can colonise the site but it is not spreading very fast.
In the invaded region, R. multiflora mainly occurs in shrub vegetation with other woody species, often climbing on trees and taller shrubs. Feral individuals were found in ornamental woody vegetation (including the CULS campus) but also in semi-natural vegetation on the river bank. Thus, we recommend to avoid planting the original type of R. multiflora in areas where it can escape and invade natural vegetation and to select for cultivated varieties with a lower invasion potential.
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