Phytoremediation, i.e. recovering the health of soils or sediments contaminated with heavy metals by using green vegetation has today been a stimulating challenge for research and solutions in environmental protection all over the world. Among the phytoremediation processes, it is the in-situ inactivation technique that has special significance, since it reduces the dangers caused by the potential toxic impacts of heavy metals. Due to the vegetation providing green surfaces, the phytoremediation processes are environmentally friendly and cost-effective (10-12% percent of traditional methods). This paper presents the results of the floristical and vegetation examinations performed in the units of a former secondary sedimentation pond system in Hungary. The outcome of analyses on the chromium content of the plants will also be discussed.