Construction of green zones in urban areas is of great importance in urban environment. Various vegetation and substrates have been suggested, but little information is available about moss as a target vegetation for green zones including rooftop greening. This study aims to test the feasibility of construction of Sphagnum wetlands in urban ecosystems by collecting basic information about Sphagnum growth and decomposition. We constructed 12 groups of Sphagnum microcosms (1m x 1m) with three replicates. A factorial design with two types of plating bases (Plain planting base and planting base with water reservoir), two types of planting methods (Capitulum without stem and Capitulum with stem), and three levels of nitrogen additions (Control, 2 g N m⁻² yr⁻¹, and 6 g N m⁻² yr⁻¹) was prepared. The changes in length, dry mass and decomposition rates of Sphagnum were monitored over a growing season. Net primary production ranged between 175 – 260 g m⁻² yr⁻¹ for dry mass, and 12.1 - 26.5 ㎜/yr for the length. These values are comparable to those from natural bogs over N48 ° in latitude. Decomposition rates measured by a litter-bag method exhibited 10.9 - 21.4% mass loss per year, which are within the ranges of decomposition rates reported from natural bogs. Overall results of this study indicate that construction of Sphagnum wetlands can be successfully employed as a greening technology in urban ecosystems even in mid-latitude.