Malaysia’s cut slopes,especially for road lines accommodation,are prone to erosions and landslides.These problems mainly occur due to lack of vegetation cover and strong erosive forces.In addition,the topography factors have also become a major factor affecting soil degradation.Thus,this study is aimed at determining the effects of planting density of a selected species,namely Melastoma malabathricum;one,two,and three seedlings per box,on the erosion rate at selected slopes of different orientation(morning and evening sun) at the Guthrie Corridor Expressway,Selangor.In six months of observation,treatment with three seedlings/box on the morning sun slope showed a lower erosion rate by 69.2%than those with the same treatment on the evening sun slope.In addition,the treatment of the three seedlings recorded at month six(final observation) had the highest reduction of soil saturation level(STL),by 23.6%.Furthermore,the physiological values of the species studied,grown on the morning sun slope,were higher in terms of stomatal conductance and photosynthetic rate by 12.1%and 15.8%(three seedlings/box),respectively.The overall results showed that plant density was inversely related to the STL and erosion rate on the slope.In conclusion,a planting density of three seedlings/box and morning sun orientation gave positive effects on the plant’s physiological performance of the slope,reducing the STL,as well as alleviating the erosion rate of slope soils. Malaysia’s cut slopes, especially for road lines accommodation, are prone to erosions and landslides.These problems occur occur due lack of vegetation cover and strong erosive forces. In addition, the topography factors have also become a major factor affecting soil degradation.Thus, this study is aimed at determining the effects of planting density of a selected species, namely Melastoma malabathricum; one, two, and three seedlings per box, on the erosion rate at selected slopes of different orientation (morning and evening sun) at the Guthrie Corridor Expressway, Selangor. In six months of observation, treatment with three seedlings / box on the morning sun slope showed a lower erosion rate by 69.2% than those with the same treatment on the evening sun slope. In addition, the treatment of the three seedlings recorded at month six (final observation) had the highest reduction of soil saturation level (STL), by 23.6% .Furthermore, the physiological values ​​of the species studied, grown on the morning sun sl ope, were higher in terms of stomatal conductance and photosynthetic rate by 12.1% and 15.8% (three seedlings / box), respectively. The overall results showed that plant density was inversely related to the STL and erosion rate on the slope. conclusion, a planting density of three seedlings / box and morning sun orientation gave positive effects on the plant’s physiological performance of the slope, reducing the STL, as well as alleviating the erosion rate of slope soils.