We investigate the effects of wall-normal velocity ($V_b$) on high Schmidt number ($Sc>600$) natural convection boundary layers formed on permeable horizontal surfaces. Using integral boundary layer equations, we define a blowing parameter, $S = (Re_L^5/ Gr_L)^{1/8}$ to characterize the strength of blowing relative to the buoyancy and the viscous effects. The analysis is performed for $0.1\leq S \leq 0.26$. The upper limit being given by $Re_d = V_b\delta_v/\nue <1$ so that inertial effects in the boundary layer are small. The lower limit of $S$ ensures that there is negligible diffusive mass transfer in the species boundary layer. As expected, blowing increases the velocity boundary layer thickness and the species boundary layer thickness; the effect is felt more on the species boundary layer thickness. Blowing also increases the horizontal velocity in the boundary layers. We show that the species boundary layer thickness scales as $x(Re_x/Gr_x)^{1/4}$ while the horizontal velocity scales as $V_b (Gr_x/Re_x)^{1/4}$.