Water quality of Lake Balaton has improved significantly in recent years due to Kis-Balaton Wetland System. Many papers deal with the water purification effect of the macrophytes, but decomposing materials have an enormous nutrient load to aquatic environments. This study deals with the dissolution of different parts (leaves, stalks and rhizomes) of the reed (Phragmites australis) in water. An experiment was set up between 16 November 2017 and 23 April 2018 in the area of Lake Balaton and Kis-Balaton Wetland System. The release of total nitrogen and total phosphorus in different plant parts were monitored. Our results show that the rate of leaching was the highest in the first two weeks for both nitrogen and phosphorus. Different amounts of nitrogen and total phosphorus leaching from different plant parts were detected. The total phosphorus contents of the plant parts were around 0.1- 10% at the end of the investigated period. Higher values were measured (leaf 54.4-51.3%, stalk 78.9.81.4%, rhizome 55.4-66.0%), compared to nitrogen. According to our results there was no significant difference between the two sampling sites. The publication is supported by the EFOP-3.6.3-VEKOP- 16-2017-00008 project. The project is co-financed by the European Union and the European Social Fund.