During the three-year field research (2019-2022) in the area of the Canton of Sarajevo, we discovered many invasive plant species in localities where they had not been recorded before. Among them, Ailanthus altissima (Mill.) Swingle, Ambrosia artemisiifolia L. and Reynoutria japonica Houtt. stand out in particular due to their abundance and coverage. This study aimed to provide data on the localities where these invasive plants were found, including altitude, longitude and latitude, soil type and their floristic and phytocoenological features. Data from these localities should contribute to the creation of a database that can be used for more a efficient fight against the aforementioned invasive species. In total, 42 new localities were recorded for Ailanthus altissima, 10 for Ambrosia artemisiifolia and 15 for Reynoutria japonica. Due to their abundance and appearance, Ailanthus altissima and Reynoutria japonica have already become a big problem for urban horiculture in Sarajevo, while Ambrosia artemisiifolia poses a health concern, and therefore, urgent measures and necessary to remove them.

Ragweed is a neophyte which inhabits various crops and ruderal habitats. That is the reason why this paper is dedicated to phytocenology and ecological relations of ragweed in such a habitat. Research was carried out in the area of a former railway freight and customs terminal, in the period from 2021 to 2023. Phytocenological image was made and all the parameters were assessed: life form, phytocenological affiliation, floral elements, indicator values, and soil analysis. The aim of the paper is to present the places where ragweed may be found, as well as under what ecological conditions and with what other species it occurs. This research yielded new data on the phytocenology of ragweed, determined in the vegetation of the order Chenopodietalia. A total of 69 species from 23 families were identified. The most numerous is the Asteraceae family. Phytocenologically, the largest number of species belongs to the order Chenopodietalia, and as far as the indicator values are concerned, the most numerous are the representatives of tertiary vegetation. Hemicryptophytes predominate regarding life forms, and concerning the floral elements, 40 different elements from 9 groups were noted. The most numerous group are Eurasian species, and the most numerous individual floral elements are euras-smed and eurassubozean-smed.