We studied plant biomass production and nutrient accumulation by wood club-rush (Scirpus sylvaticus) and reed (Phragmites australis) in a horizontal subsurface flow constructed wetland in 2001 and 2002. The wetland consists of two beds, one with dry and another with wetter conditions. From both beds, 5 above-ground, below-ground, and litter samples were taken in the summer, during the maximum flowering period of the dominant species. The average dry biomass of whole plant and litter was considerable higher in 2002 (3071 g m(-2)) than in 2001 (620 g m(-2)) due to the climatic conditions. The average dry weight biomass of 5 plots in 2001 was 513 g m(-2) in the dry bed and 729 g m(-2) in the wet bed. In 2002 these values were 2,520 and 3,765, respectively. Variations in biomasses will also appear in values for nutrient accumulation, in all cases the N and P accumulation was higher in 2002. The average nitrogen accumulation by plants was 16.6 g m(-2) in the wet and 10.7 g m(-2) in the dry bed in 2001, and 51.7 and 83.5 g m(-2) in 2002 respectively. Phosphorus accumulation was higher in the wet bed during 2001--2.8 g m(-2), in the dry bed this value was 1.9 g m(-2). In 2002, the phosphorus accumulation was higher in the dry bed--12.8 g m(-2), in the wet bed it was 12.43 g m(-2). The total biomass at the same conditions in the wet bed was slightly higher in case of wood club-rush--765 g m(-2) in 2001 and 3846 g m(-2) in 2002, same values for reed were 674 g m(-2) and 3,646, respectively.