This research evaluated the effectiveness of organic matter ratios in substrate and mulching materials under mn-irrigated condition green roofs by measuring the effects on growth of Liatris spicata. Four mulching materials were installed, i. e. nun-mulched control(CON), volcanic ash soils(VAS), non-woven black fabric mat(NBM) and pine bark(PAK). Three levels of organic maller volume percentage in an amended soil were evaluated, amended soil: organic matter=100:0($A_1O_0$), amended soil: organic matter=80:20($A_4O_1$) and amended soil: organic matter=50:50($A_1O_1$). Plant height, number of leaves, diameter of flower stalk, number of florets, chlorophyll contents, shoot fresh and dry weight were recorded from April to September, 2010, and survival rate was examined on May 2011 of the following year. In the $A_1O_0$, the number of leaves, number of florets and chlorophyll contents were higher in Liatris spicata grown on NBM than other mulching treatments. Especially, plant height, shoot fresh and dry weight were significantly higher. However, it resulted the lowest survival rate than other mulching treatments. 2. In the $A_4O_1$, the plant height, number of leaves, number of florets, shoot fresh and dry weight were higher than other mulching treatments, but there was no significant difference except for the plant height of Liatris spicata grown on NBM. The survival rate was decreased by 40~60%, compared with $A_1O_0$, after overwintering. 3. In the $A_1O_1$, the plant height, number of leaves, diameter of flower stalk, number of florets, chlorophyll contents, shoot fresh and dry weight were slightly higher than other mulching treatments, but there was no significant difference from Liatris spicata grown on NBM and VAS. The survival rate was observed by 0% over all mulching treatments after overwintering. Therefore, the non-woven black fabric mat(NBM) promoted the Liatris spicata's growth and flowering compared with other mulching treatments. However, the survival rate was decreased significantly, and the organic matter ratios were increased after overwintering under non-irrigated green roofs.