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Systematic studies carried out in the greenhouses of the Botanical Garden - Center for Biological Diversity Conservation of the Polish Academy of Sciences in Warsaw-Powsin revealed that the flora of weeds ras very rich there. A total of 243 taxa of vascular plants and 17 species of bryophytes were recorded. With regard to the division of the flora of vascular plants according to species origin and degree of naturalization, it was found that native plants (89 species), greenhouse-escapes (87 species) and permanently established aliens (48 species) co-dominated there. In addition, 10 species of garden-escapes, i.e. plants cultivated in the immediate neighbourhood of greenhouses, were recorded indoors. Noteworthy were two species that had been brought accidentally to the glasshouses together with plant material - this group of plants is least numerous but quite frequent in the study area. Observations made in the vicinity of Powsin greenhouses showed that relationships between the studied flora and the plants growing outside were unilateral. In Powsin no proved example of expansion of greenhouse plants to other parts of the Garden has been recorded. By contrast, influx of diaspores to the study area is observed frequently - the flora of greenhouse weeds is dominated by plants found also in the immediate neighbourhood (147 species). The most important factors affecting the composition of the weed flora of glasshouses include the flora of the surrounding areas and the mode of greenhouse management (e.g. the range of species cultivated there). The diversity of the flora is not related to greenhouse size.
Galera et al. (Mon,) studied this question.