Add grass with today’s tutorial!
Select the Brush tool (B) and click the brush preview. Select the single blade of grass brush. Set your Foreground colour to a bright green. Paint in large sweeping strokes across the base of the image. This will mostly be hidden so doesn’t need to look realistic.
Set a more conservative green as your Foreground colour and on a new layer, start painting more carefully. This will help you control the Jitter and Scattering effects that are applied to the brush. Vary your green while you’re painting, for realism.
Create a new layer and increase the size of your paint brush. Paint blades of grass in the foreground, using single clicks. Go to Filter>Blur>Lens Blur and apply a blur to these front blades, setting the Radius to about 30, Curvature: 94, Rotation: 360.
Make colour tweaks to integrate the grass. Try adding a Gradient Map adjustment layer. Use dark greens and blacks and make that adjustment layer a clipping mask to a group containing your grass layers. Set blend mode to Hard Light.